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Simulated impact of a change in fish consumption on intake of n-3 polyunsaturated fatty acids
Journal of Food Composition and Analysis 22 (2009) 657–662
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Original Article
Simulated impact of a change in fish consumption on intake of n-3 polyunsaturated fatty acids Ying Zhang a,b,*, Satoshi Nakai a, Shigeki Masunaga a a b
Graduate School of Environment and Information Sciences, Yokohama National University, 79-7 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan School of Environment and Biological Science and Engineering, Dalian University of Technology, No. 2 Linggong Road, Dalian 116024, China
A R T I C L E I N F O
A B S T R A C T
Article history: Received 9 August 2008 Received in revised form 28 January 2009 Accepted 2 March 2009
The objective of this study was to elucidate the impact of a change in fish consumption on the intake of long chain n-3 polyunsaturated fatty acids (LC n-3 PUFA), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) by Japanese women. A probabilistic assessment model for EPA&DHA intake was first proposed to describe the relationship between fish consumption and EPA&DHA intake, and was compared with the survey data. Various scenarios were designed for women representing potential responses to an advisory on fish consumption recently issued in order to avoid risks associated with intake of methyl mercury (MeHg). Elimination of women’s consumption of fish species with high and medium levels of MeHg resulted in a reduction of EPA&DHA intake from 0.85 g/d to 0.82 g/d. The percentage of women with an EPA and DHA intake over 0.25 g/d also decreased from 99.5% to 99.0%. The model results suggested that the changes in fish consumption related to MeHg advisories have a minor influence on the intake of EPA&DHA and on the percentage of women with EPA&DHA intake exceeding the guideline for Japanese women. Nevertheless this simulation could aid the selection of fish species in order to ensure adequate intake of EPA&DHA while minimizing exposure to MeHg. ß 2009 Elsevier Inc. All rights reserved.
Keywords: EPA&DHA n-3 polyunsaturated fatty acids (n-3 PUFA) Intake assessment Fish consumption Japanese women Methyl mercury (MeHg) Food analysis Food composition
1. Introduction Consumption of fish or seafood is important because of its positive effects on human health. Recent studies indicate that an adequate consumption of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the important long chain n-3 polyunsaturated fatty acids (LC n-3 PUFA), can help to protect humans against several adverse health effects, including mortality due to coronary heart disease (CHD), and stroke, as well as cancer. (Bouzan et al., 2005; Colombo et al., 2004; Iso et al., 2006; Kris-Etherton et al., 2002; MacLean et al., 2006; Wakai et al., 2005a). Humans are unable to synthesize EPA and DHA in their body at a sufficient level and, therefore, they must obtain them from their diet. Fish is a rich dietary source of LC n-3 PUFA, especially EPA and DHA. Most of the EPA and DHA found in the human body are derived from fish (Tokudome et al., 1999). Among the LC n-3 PUFA, DHA may be especially critical for the developing brain in uterus (Cohen et al., 2005; Daniels et al., 2004), since the fetus must obtain DHA directly from the mother. Although fish is a rich source of LC n-3 PUFA, it may also contain methyl mercury (MeHg), a neurotoxin that may adversely affect the development of the brain and nervous system. Epidemiological studies in the Faroe Islands, Seychelles, and New Zealand indicate
* Corresponding author. Tel.: +86 411 8470 6251; fax: +86 411 8470 6252. E-mail address: [email protected] (Y. Zhang). 0889-1575/$ – see front matter ß 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.jfca.2009.03.007
that even low-dose chronic exposure to MeHg through fish consumption leads to cognitive developmental delays in children (Myers et al., 2000; Yokoo et al., 2003; Zahir et al., 2005). Moreover, fetuses have been identified as the population most sensitive to MeHg exposure through maternal fish consumption (NRC, 2000). In order to avoid the risk related to MeHg, the US Food and Drug Administration recommends that pregnant women, women who might become pregnant, young children and nursing mothers modify their fish consumption pattern (USFDA, 2001, 2004). This advisory has been taken up in other countries, including Japan (CFIA, 2002; MHLW, 2003a; UKFSA, 2003). Specifically, the advisory issued in Japan (MHLW, 2003a) recommends that women of child-bearing age modify their seafood consumption. The marine species designated in the advisory, such as bottlenose dolphin, whale, blackfish, shark, swordfish and splendid alfonsino, should be reduced to a limited amount, i.e. a consumption pattern of less than once every two weeks, once every month, or once every two months. In 2005, the advisory was revised to include 16 species. Fish consumption incurs both PUFA-related benefits and MeHgrelated risks. Therefore, the advisories issued in order to avoid MeHg-related risk may raise another kind of risk, namely that of lower EPA&DHA intake. To avoid MeHg-related risk, people could either reduce the amount of fish consumed or modify the fish species they consume. However, the impact of these changes on EPA&DHA intake has not been clearly shown. To assess the
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potential impact of the advisory, and to help people understand the impact of these modifications on EPA&DHA intake, we designed a population-based model of EPA&DHA intake and simulated the impact of shifts in fish consumption on EPA&DHA intake for the Japanese population. Our PUFA intake model aimed to describe the relationship between EPA&DHA intake and fish consumption. It was constructed based on fish consumption by individual, species-specific fish market share, and EPA&DHA concentration in fish. Then the estimated EPA&DHA intakes from our proposed model were compared with the reported data from a dietary survey study conducted in Japan (Okuda et al., 2005) as part of the International Study of Macronutrients and Blood Pressure (INTERMAP). Next, the impact of shifts in fish consumption on EPA&DHA intake was estimated only for women by simulating the EPA&DHA intake under various scenarios using the proposed PUFA intake model. A number of scenarios were simulated in order to analyze alternative choices for avoiding the MeHg-related risk from fish consumption, and to describe different patterns of fish consumption that consumers may choose in response to the advisories. 2. Data and methodology
Fish groups
Fish name
Market sharea (%)
EPA&DHAb (mg/g)
Tuna
Yellowfin tuna Bluefin tuna Albacore tuna Southern bluefin Bigeye tuna Other tuna
33.8 3.4 19.2 1.9 35.0 6.7
0.75 1.47–46 1.87 0.09–40 2.3 11.6
Seabream and Flat fish
Red seabream Porgy Black seabream Flounder Flatfish
46.2 3.8 2.3 40.0 7.6
9.1–18.7 4.4 6.7 1.64–11.8 4.1–6.7
a Market share was estimated from the domestic fish catch amounts (MAFF, 1995). b EPA&DHA data were adopted from the standard tables of food composition (fifth revised and enlarged edition, fatty acids section) MEXT (2005). EPA&DHA concentration is given as a range, when more than one EPA&DHA level provided in the database (MEXT, 2005); EPA&DHA concentration is given as one value, while only one value of EPA&DHA level provided in the database.
based on the data taken from the U.S. Department of Agriculture Continuing Survey of Food Intake by Individuals (CSFII) (USDA, 1998). These data were kindly provided by Dr. Carrington from USFDA, one of the authors of Carrington and Bolger (2002).
2.1. PUFA intake model 2.1.1. Species-specific fish consumption Fish consumption data for Japanese individuals were adopted from the Health and Nutrition Information Infrastructure Database System (HNIIDS, 1995) by National Institute of Health and Nutrition, which was constructed based on the National Nutrition Survey (NNS, 1995) in Japan. The NNS is carried out using a questionnaire on a day in the month of November every year, and the respondents are required to perform 24-h recall. The NNS is the representative diet and nutrient survey in Japan. More than 15,000 respondents are involved in the NNS, and over 95% of the consumers reported their fish consumption. In the HNIID database, the fish consumed were not given as the fish species directly consumed in the one-day record by each respondent, but reported as mean value and standard deviation (S.D.) of 13 fish groups for various population groups (i.e. children (1–6 years), women, men and total population). The mean and S.D. were reported based on the cumulative statistics for only those individuals who reported consumption of seafood on the survey day, according to the questionnaires of the one-day diet record. In order to capture the variability of EPA&DHA intake from each species, the concentration of EPA&DHA in the various fish species had to be considered. However, the EPA&DHA concentrations differed considerably within the 13 fish groups reported in the HNIID database. Thus, the market-weight shares within each fish group were used to divide 13 fish groups into 58 fish species groups. The market-weight shares within each group were estimated for each species based on the weight of domestic catches reported by the Ministry of Agriculture, Forestry and Fisheries of Japan (MAFF, 1995) (examples listed in Table 1). Thus, species-specific fish consumption by an individual was estimated based on the reported fish consumed by the individual and species-specific market share of fish, using the following formula: Mi ¼ M j F k j
Table 1 Examples of market share and EPA&DHA level in some fish species.
2.1.2. PUFA levels in fish The EPA&DHA level in each species depends heavily on the preparation methods, e.g. raw, steamed, or fried (MEXT, 2005). The range (minimum to maximum) of EPA&DHA level for each species prepared in different ways was taken from the Standard Tables of Food Composition (Edition 5), issued by Ministry of Education, Culture, Sports, Science, and Technology of Japan (MEXT, 2005). Some examples of EPA&DH levels in fish species are given in Table 1. Since the relevant data are difficult to collect, the distribution of EPA&DHA level in each fish species has been difficult to describe until now, therefore, the distribution of EPA&DHA levels in each fish species was assumed to be uniform simply. 2.1.3. Estimating PUFA intake Daily individual PUFA intake was estimated using the following formula: X D¼ ðC i M i Þ (2) i
where D is the daily PUFA intake; i is fish species; Ci is PUFAs level in the ith fish species; and Mi is the consumption of the ith fish species.
(1)
where Mi is an individual’s intake of fish of the ith species; Mj is the daily intake of fish of the jth group; and Fkj isX the market share of 13 kth fish species in jth fish group (j = 13, i ¼ k j ¼ 58). The distribution of the fish consumed j¼1 was assumed to be lognormal, similar to the fish consumption pattern reported for Americans (Fig. 1) according to the likelihood empirically. Fig. 1 is
Fig. 1. Daily fish consumption pattern of Americans.
Y. Zhang et al. / Journal of Food Composition and Analysis 22 (2009) 657–662
The distribution of PUFA intake among population was simulated using Crystal Ball1 with Monte Carlo simulation. Specifically, Crystal Ball1 was used to estimate the output by combining randomly sampled amounts of fish species consumed by an individual with PUFA concentration in each fish species. These samples were generated randomly from two database sets: (i) the distribution of consumed fish and (ii) the distribution of PUFA levels in these fish species. The sampling process was repeated 100,000 times, which was considered to sufficiently represent the variability of the PUFA intake, for each sex and age group. 2.2. Scenarios To simulate the influence of different risk management options on EPA&DHA intake, some hypothetical scenarios were designed to represent potential consumer responses to the advisory. The scenarios considered changes in both choice of fish species and amounts of each fish species consumed, assuming that these changes would be completely accurate throughout the entire fish market. The impact of changes in fish consumption on the EPA&DHA intake under these scenarios was simulated for only women, since women are the primary target population of the advisory. Scenario 0 corresponds to the baseline (no changes in response to the advisory). Scenario 1 is somewhat less optimistic. The advisory issued in Japan recommends that women of child-bearing age avoid consuming fish species with high MeHg concentration. In this
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scenario, women were assumed to misinterpret the advisory, such that they decreased their total fish consumption by 12% but did not change the fish species consumed. This extent of reduction in fish consumption was assumed to be at the same extent across all fish species, and was applied based on the fact that total amount of fish consumption has reported decreased by approximately 12% following the issuance of the advisory issued in 2003 (MHLW, 2003b). It was impossible to say with certainty whether the 12% reduction was due entirely to the advisory; nevertheless, this reduction served to indicate potential changes in consumption. Scenario 2 corresponds to an optimistic response to the advisory. In the advisory, fish were categorized into three groups based on their concentration of MeHg: high (MeHg concentration >0.4 mg/g), medium (MeHg concentration of 0.14–0.4 mg/g), and low (MeHg concentration <0.14 mg/g) (Table 2). This scenario assumes that only low-MeHg fish were consumed by women of child-bearing age, which leads to a reduction in overall fish consumption. Scenario 3 is similar to scenario 2, but differs in that only highMeHg fish species were eliminated by women. Scenario 4 represents the ideal response to the advisory. In addition to not consuming high- or medium-MeHg fish, women maintained the same overall amount of fish consumption by increasing their consumption of low-MeHg fish. This scenario was considered more optimistic than scenario 2, because it allowed for women to maintain their pre-advisory LC n-3 PUFA intake. Scenario 5 describes a response opposite to that of scenario 1. Under this scenario, women increased their overall fish consumption by 12%, assuming that they completely relied on the health
Table 2 EPA&DHA and MeHg concentrations in some fish species. Groups based on the advisory
Fish species
MeHga (mean, mg/g)
High
Swordfish Bigeye tuna Bluefin tuna Southern bluefin
0.67 0.57 0.54 0.40
6.4 2.3 1.47–46 0.09–40
Medium
Shark Marlin Porgy Other tuna Perch Black seabream Yellowtail Tilefish Snow crab Blue marlin Yellowfin tuna Albacore tuna
0.36 0.35 0.33 0.31 0.27 0.21 0.20 0.20 0.19 0.19 0.18 0.16
0.59–11.2 3.71 4.4 11.6 4.5 6.7 26.4–29 4.2–5.9 0.73–1.5 0.4 0.75 1.87
Low
Red seabream Frigate mackerel Skipjack Canned tuna Flatfish Sand lance Mackerel Sea bass Cod roe Alaska pollock Atka mackerel Cutlass fish Cod & Hake Sardine Eel Trout
0.13 0.13 0.12 0.11 0.08 0.08 0.07 0.07 0.07 0.06 0.06 0.05 0.05 0.05 0.05 0.05
9.1–18.7 6.5 1.12–13.7 0.79–5.5 4.1–6.7 9.5–14.2 12–44 7 9.5–14.3 0.58–1.14 8.3–9.8 23.7 0.56–1.74 9.5–9.7 16.1–20.5 6.9–21.9
a
EPA&DHAb (mg/g)
DHAb (mg/g) 5.3 1.9 1.2–32 0.07–27 0.5–6.9 3.1 3.3 8.5 2.5 4.1 17–19 2.7–3.9 0.33–0.5 0.36 0.65 1.5 8.9–11 4.7 0.88–9.7 0.65–4.4 2.9–4.5 5–7.7 7–27 4 5–7.8 0.34–0.67 3.5–5.3 14 0.42–1.1 6.6 0.47–13 4.9–14
MeHg data were adopted from the MeHg levels in fish (MHLW, 2004). EPA&DHA data were adopted from the standard tables of food composition (fifth revised and enlarged edition, fatty acids section) (MEXT, 2005). The groups based on the advisory: high means MeHg level in fish over 0.4 mg/g; medium means MeHg level between 0.14 and 0.4 mg/g, and low means MeHg level below 0.14 mg/g. EPA&DHA concentration is given as a range, when more than one levels are available in the database (MEXT, 2005); EPA&DHA concentration is given as one value, while only one value of level available in the database. b
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3.2. Daily PUFA intake for women under different scenarios
Table 3 EPA&DHA intake from fish consumption for Japanese population. Percentile (g/day)
Women
Men
Total
Mean 2.5th 5th Median 90th Percentage >0.25 g/d
0.85 0.31 0.35 0.70 1.81 99.5%
1.02 0.38 0.43 0.85 2.15 99.9%
0.93 0.35 0.39 0.70 1.81 99.8%
Table 4 Comparison of n-3 PUFA intake between INTERMAP study and this study. n-3 PUFA (g/day)
Data
Women, mean (S.D.)
Men, mean (S.D.)
EPA&DHA
This study INTERMAP (Okuda et al., 2005)
0.85 (0.70) 0.88 (0.56)
1.02 (0.77) 1.20 (0.73)
This study INTERMAP (Okuda et al., 2005)
0.51 (0.38) 0.56 (0.33)
0.62 (0.47) 0.75 (0.43)
DHA
Note: Women and men referred belonged to all age segments in life span in this study; while women and men aged 40–59 years were involved in Okuda et al. (2005).
benefits, but regardless of the health risk related to fish consumption. 3. Results 3.1. Estimated results of PUFA intake Utilizing the proposed intake model, EPA&DHA and DHA intakes were estimated for all Japanese as well as for women and men. The estimated results with mean, median and several percentiles are given in Table 3. The mean value of EPA&DHA intake for women is 0.85 g/d, with a median of 0.70 g/d and 90th percentile of 1.81 g/d. Okuda et al. (2005) conducted a dietary survey in Japan (n = 572 men and 570 women), within the context of the International Study of Macronutrients and Blood Pressure (INTERMAP), which was one of the largest studies on daily PUFA intake in Japan. In their study, the n-3 PUFA intakes for men and women aged 40–59 years were reported with means and standard deviations (see Table 2 in Okuda et al., 2005). We applied their results to compare with our estimations. Table 4 illustrates the comparison of the two studies, and it shows that our results are somewhat underestimated compared with those of the INTERMAP study.
The proposed intake model was utilized to estimate EPA&DHA intake under various scenarios. Table 5 gives the simulated results for each scenario, expressed in terms of EPA&DHA intake, as well as the percentage of population achieving or exceeding the guideline. The results illustrate that eliminating fish species with high- and medium-MeHg levels resulted in the reduction of EPA&DHA intake from 0.85 g/d to 0.82 g/d (from baseline to scenario 2). When the eliminated amounts of high- and medium-MeHg fish were compensated for by increasing consumption of other fish species, EPA&DHA intake increased from 0.82 g/d to 0.89 g/d (from scenario 2 to scenario 4). 4. Discussion The primary motivation of this study was to demonstrate the impact of changes in fish consumption on EPA&DHA intake among Japanese women. A probabilistic PUFA intake model was proposed to provide an analytical tool that relates EPA&DHA intake to fish consumption. Our estimations were somewhat underestimated for both women and men compared to the survey data from Okuda et al. (2005); however, the similarity of our model’s results with those of the INTERMAP study suggests that the model is satisfactory for simulating the PUFA intake from fish consumption (see Table 4). The intake of n-3 PUFA was illustrated to protect humans against several adverse health effects, e.g. heart diseases and stroke. Accordingly, a number of countries and organizations have made formal, population-based dietary recommendations on LC n-3 PUFA intake. In Japan, the dietary reference intake on LC n-3 PUFA was issued, but not on EPA&DHA, where LC n-3 PUFA refer to C18:3, C18:4, C20:4, C20:5 (EPA), C21:5, C22:5 and C22:6 (DHA). In this issue, the adequate dietary intake of LC n-3 PUFA for women (above 6 years) was recommended to be more than 2.2 g/d (MHLW, 2005). Typical recommendations are 0.3– 0.5 g/d of EPA&DHA for healthy people (Kris-Etherton et al., 2002). The meta-analysis of Mozaffarian and Rimm (2006) found that an average daily intake of 250 mg of EPA&DHA was sufficient for optimal protection against heart attacks. Since there is no guideline on EPA&DHA intake in Japan, we applied the recommendation of 250 mg/d of EPA&DHA intake as the guideline to Japanese. Our simulations showed that 99.8% of the Japanese population consume more than 0.25 g/d of EPA&DHA at the baseline (Table 3), indicating that nearly all Japanese people consumed an adequate amount of EPA&DHA, defined as 0.25 g/d, through fish consumption.
Table 5 EPA&DHA intake for Japanese women under various scenarios. Scenario
0 1 2 3 4 5
Mean fish consumption (g/d)
88.2 77.6 81.1 85.5 88.2 98.8
(EPH + DHA) intake (g/d) Mean
2.5th percentile
5th percentile
Median
95th percentile
0.85 0.75 0.82 0.83 0.89 0.95
0.31 0.28 0.29 0.30 0.31 0.35
0.35 0.31 0.33 0.33 0.35 0.39
0.70 0.61 0.67 0.68 0.73 0.78
1.80 1.58 1.77 1.80 1.93 2.02
Note: Women referred belonged to all age segments in the life span. Scenario 0: represents baseline. Scenario 1: fish consumption decreased by 12%. Scenario 2: only fish with low MeHg (<0.14 mg/g) consumed. Scenario 3: fish with high MeHg (>0.4 mg/g) avoided to consume. Scenario 4: fish with low MeHg (<0.14 mg/g) consumed, and the overall consumption amount maintained by increasing low-MeHg fish. Scenario 5: fish consumption increased by 12%.
Percentage of EPA&DHA >0.25 g/d (%) 99.5 98.7 99.0 99.2 99.4 99.8
Y. Zhang et al. / Journal of Food Composition and Analysis 22 (2009) 657–662
To reduce MeHg exposure by simply reducing the amount of highMeHg fish can lead to a reduction in EPA&DHA intake. Eliminating the high- and medium-MeHg fish species, resulting in the reduction of overall fish consumption, led to decreased EPA + DHA intake by women from 0.85 g/d in the baseline to 0.82 g/d in scenario 2 (Table 5). It illustrated that the changes in consumption related to MeHg advisories have a minor influence on the intake of EPA&DHA. This is because few of the fish species that recorded high levels of EPA&DHA also had high MeHg levels. Such that avoiding intake of fish species with high MeHg levels did not necessarily eliminate high EPA&DHA containing fish species. However, when the overall fish consumption was maintained by increasing the consumption of fish species with a low level of MeHg, EPA + DHA intake increases from 0.82 g/d in scenario 2 to 0.89 g/d in scenario 4. It suggested that EPA&DHA intake could be reconverted by maintaining overall fish consumption. In addition, people could increase their EPA&DHA intake by selecting fish species low in MeHg and high in EPA&DHA. As shown in Fig. 2, the fish species located at the upper left are preferred. There are two methods to avoid MeHgrelated risk: one is to reduce overall fish consumption, and the other is to eliminate consumption of high- or medium-MeHg fish species. The simulated results showed that a greater percentage of Japanese women took in more EPA&DHA than what the guideline prescribed when more fish was consumed. This comparatively higher EPA&DHA intake seemed to be correlated with greater fish consumption. This suggests that the strategy to reduce MeHg exposure by reducing the amount of fish consumption has a greater impact on PUFA intake than the strategy to change the fish species consumed. However, relations between MeHg and EPA&DHA concentrations in seafood may be different depending on countries, thus present results may be specific for Japanese women. The simulated results under various scenarios showed that the percentages of women with over 0.25 g/d EPA + DHA intake changed with the change of fish consumption. However, the percentage of women with over 0.25 g/d EPA + DHA intake in each scenario were still more than 99% (except scenario 1), which suggests that the elimination of consumption of fish species with high and/or medium levels of MeHg has quite limited effect on the EPA&DHA intake. This impact may be explained by the fact that the overall amount of fish consumption by Japanese population is very large, while fish species with high MeHg concentration might not necessarily contain high EPA&DHA concentration.
Fig. 2. MeHg and (EPA + DHA) concentrations in some fish species.
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EPA&DHA intake was estimated from fish consumption in this analysis. However, it should be noted that EPA&DHA could also be obtained from other sources of food, such as eggs, meats, and milk. Mahaffey et al. (2008) noted that fish consumption accounted for the majority of the intake of EPA + DHA. Similarly, it has been suggested that fish are the main source of DHA for Japanese individuals, and that fish intake explains more than 90% of the inter-individual variation in EPA intake (Tokudome et al., 1999). These findings indicate that changes in fish consumption can cause changes in EPA&DHA intake. In addition to estimating the dietary EPA&DHA intake, it would also be useful to estimate the body (blood or serum) levels of EPA&DHA. This is because the body EPA&DHA levels would be directly related to the derived health benefits. The dietary EPA&DHA intake from fish consumption was reported to be related to the body (blood or serum) levels for the Japanese (Kuriki et al., 2003; Kobayashi et al., 2003; Wakai et al., 2005b). However, the quantitative relationship between them is not available; hence we could not estimate the body levels from the dietary EPA&DHA intake. We compared our estimations using the proposed model with the empirical data from the INTERMAP study, which showed that our estimations were comparatively lower. This may be explained from several respects. The age ranges of participants were different for the two studies: the subjects recruited in INTERMAP study were aged 40–59 years, while women of all age segments of life span were recruited in this present study. In addition, some assumptions presently made for the purpose of this EPA&DHA intake assessment may also cause some errors in our results, such as the market share and distribution patterns of PUFA. The market share of each fish species was calculated based on the domestic fish catch amounts reported by MAFF, though only half of the fish consumed were caught domestically (MAFF, 1995). Therefore, taking the import portion of fish into consideration may improve the intake assessment. The distribution of EPA&DHA levels in each fish species was simply assumed to be uniform. Sioen et al. (2007) constructed a nutrient database based on 14 food composition databases from various countries. The fish species consumed by the Japanese were focused in this study, so we did not apply their database. However, better selection of distribution patterns may improve the resulting estimations. Moreover, the consumption data used were adopted from the survey in 1995, which were the only one available for the public until now although they were rather old. The estimation would be updated as the fish consumption got updated in the future. It should be noted that there are some other contaminants present in seafood, e.g. dioxins-like compounds, polychlorinated biphenyls, and other heavy metals (As, Pb, etc.). MeHg was focused on in this analysis in view of the fact that fish is the most important dietary source of mercury in the human diet. Additionally, changes in fish consumption would possibly influence the exposure to other contaminants, although it was not taken into account here. Sioen et al. (2008a,b) have presented the relation between dioxin exposure and EPA&DHA intake from fish consumption. Considering the fish consumption associated health benefits, the hazards from other contaminants should also be taken into account. Since survey data are probably more reliable than the derived predictions from a simulation, the purpose of this simulated intake assessment was much of one that could provide an analysis tool to relate EPA&DHA intake with fish consumption and EPA&DHA level in fish across the Japanese population. This EPA&DHA intake model is considered to be useful in simulating the changes in EPA&DHA intake when fish consumption changes. The results of this analysis may be expanded to predict the change in health benefits when combined with dose–response relationships. Essentially, this analysis may be particularly useful as part of risk-benefit analysis.
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5. Conclusions To reduce MeHg exposure by simply reducing the amount of high-MeHg fish could lead to a reduction in EPA&DHA intake, which was demonstrated quantitatively using the developed assessment model and designed scenarios for women. Eliminating fish species with high and medium levels of MeHg led to a quite limited reduction of the EPA&DHA intake among Japanese women population. While avoiding the risk associated with MeHg from fish consumption, the EPA&DHA intake could be maintained by maintaining the overall fish consumption or selecting fish species low in MeHg and high in EPA&DHA. Additional attention should be paid to the exposure to other contaminants, e.g. dioxins and polychlorinated biphenyls, which would also be changed along with the fish consumption. Nevertheless, this simulation has the potential to aid the selection of fish species in order to ensure adequate intake of EPA&DHA while minimizing exposure to MeHg, and may be particularly useful as part of risk-benefit analysis. Acknowledgements The authors thank the anonymous reviewers for their constructive comments and suggestions. Thanks from the authors also to Mr. Jonathan N. Hogarh, and Dr. Vasu Tiwari, both of Yokohama National University for their constructive comments on our manuscript. References Bouzan, C., Cohen, J.T., Connor, W.E., Kris-Etherton, P.M., Gray, G.M., Konig, A., Lawrence, R.S., Savitz, D.A., Teutsch, S.M., 2005. A quantitative analysis of fish consumption and stroke risk. American Journal of Preventive Medicine 29, 347–352. Carrington, C.D., Bolger, P.M., 2002. An exposure assessment for methyl mercury from seafood for consumers in the United States. Risk Analysis 22, 689–699. CFIA, 2002. Food Inspection Agency, Canada. Retrieved June 18, 2008 from: http:// www.inspection.gc.ca/english/fssa/concen/specif/mercury.shtml. Cohen, J.T., Bellinger, D.C., Connor, W.E., Shaywitz, B.A., 2005. A quantitative analysis of prenatal intake of n-3 polyunsaturated fatty acids and cognitive development. American Journal of Preventive Medicine 29, 366–374. Colombo, J., Kannass, K.N., Shaddy, D.J., Kundurthi, S., Maikranz, J.M., Anderson, C.J., Blaga, O.M., Carlson, S.E., 2004. Maternal DHA and the development of attention in infancy and toddlerhood. Child Development 75, 1254–1267. Crystal Ball1, 2000. Decisioneering, professional edition, Japanese version. Daniels, J.L., Longnecker, M.P., Rowland, A.S., Golding, J., ALSPAC Study Team, 2004. Fish intake during pregnancy and early cognitive development of offspring. Epidemiology 15, 394–402. HNIIDS, 1995. Health and Nutrition Information Infrastructure Database System. Retrieved November 18, 2006 from: http://www.nih.go.jp:888 (being locked now due to some reasons, in Japanese). Iso, H., Kobayashi, M., Ishihara, J., Sasaki, S., Okada, K., Kita, Y., Kokubo, Y., Tsugane, S., JPHC Study Group, 2006. Intake of fish and n-3 fatty acids and risk of coronary heart disease among Japanese. Circulation 113, 195–202. Kobayashi, M., Sasaki, S., Kawabata, T., Hasegawa, K., Tsugane, S., 2003. Validity of a self-administered food frequency questionnaire used in the 5-year follow-up survey of the JPHC Study Cohort I to assess fatty acid intake: comparison with dietary records and serum phospholipid level. Journal of Epidemiology 13 (1 Suppl.), s64–s81. Kris-Etherton, P.M., Harris, W.S., Appel, L.J., 2002. Fish consumption, fish oil, omega3 fatty acids, and cardiovascular disease. Circulation 106, 2747–2757. Kuriki, K., Nagaya, T., Tokudome, Y., Imaeda, N., Fujiwara, N., Sato, J., Goto, C., Ikeda, M., Maki, S., Tajima, K., Tokudome, S., 2003. Plasma concentrations of (n-3) highly unsaturated fatty acids are good biomarkers of relative dietary fatty acid intakes: a cross-sectional study. The Journal of Nutrition 133 (11), 3643–3650. MacLean, C.H., Newberry, S.J., Mojica, W.A., Khanna, P., Issa, A.M., Suttorp, M.J., Lim, Y.-W., Traina, S.B., Hilton, L., Garland, R., Morton, S.C., 2006. Effects of omega-3 fatty acids on cancer risk: a systematic review. Journal of the American Medical Association 295, 403–415.
MAFF, 1995. Domestic Fish Catch Amounts. The Ministry of Agriculture, Forestry and Fisheries, Japan. Retrieved June 18, 2008 from: http://www.jfa.maff.go.jp (in Japanese). Mahaffey, K.R., Clickner, R.P., Jeffries, R.A., 2008. Methylmercury and omega-3 fatty acids: co-occurrence of dietary sources with emphasis on fish and shellfish. Environmental Research 107, 20–29. MEXT, 2005. Standard Tables of Food Composition (fifth revised and enlarged edition, fatty acids section). The Ministry of Education, Culture, Sports, Science & Technology, Japan. Retrieved June 18, 2008 from: http://www.mext.go.jp/ b_menu/shingi/gijyutu/gijyutu3/toushin/5031801/004/009.pdf (in Japanese). MHLW, 2003a. The Advisory on Fish Consumption. The Ministry of Health, Labor and Welfare, Japan. Retrieved June 18, 2008 from: http://www.mhlw.go.jp/ topics/bukyoku/iyaku/syoku-anzen/suigin (in Japanese). MHLW, 2003b. National Nutrient Survey. The Ministry of Health, Labour and Welfare, Japan. Retrieved June 18, 2008 from: http://www.mhlw.go.jp/ bunya/kenkou/eiyou-chosa2-01 (in Japanese). MHLW, 2004. MeHg Levels in Fish. The Ministry of Health, Labor and Welfare, Japan. Retrieved June 18, 2008 from: http://www.mhlw.go.jp/shingi/2004/08/dl/ s0817-2q.pdf (in Japanese). MHLW, 2005. The Dietary Guideline on Fatty Acids Intake. The Ministry of Health, Labor and Welfare, Japan. Retrieved Jan 18, 2009 from: http://www.mhlw.go.jp/ houdou/2004/11/dl/h1122-2b.pdf (in Japanese). Mozaffarian, D., Rimm, E.B., 2006. Fish intake, contaminants, and human health: evaluating the risks and the benefits. Journal of American Medical Association 296, 1885–1899. Myers, G.J., Davidson, P.W., Cox, C., Shamlaye, C., Cernichiari, E., Clarkson, T.W., 2000. Twenty-seven years studying the human neurotoxicity of methylmercury exposure. Environmental Research 83, 275–285. NNS, 1995. National Nutrition Survey Database, Japan. Retrieved June 18, 2008 from: http://wwwdbtk.mhlw.go.jp/toukei/kouhyo/indexkk_14_2.html (in Japanese, with English abstract). NRC, 2000. National Research Council. Toxicological Effects of Methyl Mercury. Committee on the Toxicology Effects of Methyl Mercury. National Academy Press, Washington, DC. Okuda, N., Ueshima, H., Okayama, A., Saitoh, S., Nakagawa, H., Rodriguez, B.L., Sakata, K., Choudhury, S.R., Curb, J.D., Stamler, J., 2005. Relation of long chain n-3 polyunsaturated fatty acid intake to serum high density lipoprotein cholesterol among Japanese men in Japan and Japanese-American men in Hawaii: the INTERLIPID study. Atherosclerosis 178, 371–379. Sioen, I., De Henauw, S., Verdonck, F., Van Thuyne, N., Van Camp, J., 2007. Development of a nutrient database and distributions for use in a probabilistic riskbenefit analysis of human seafood consumption. Journal of Food Composition and Analysis 20 (8), 662–670. Sioen, I., Van Camp, J., Verdonck, F., Verbeke, W., Vanhonacker, F., Willems, J., De Henauw, S., 2008a. Probabilistic intake assessment of multiple compounds as a tool to quantify the nutritional-toxicological conflict related to seafood consumption. Chemosphere 71, 1056–1066. Sioen, I., De Henauw, S., Verbeke, W., Verdonck, F., Willems, J., Van Camp, J., 2008b. Fish consumption is a safe solution to increase the intake of long chain n-3 fatty acids. Public Health Nutrition 11, 1107–1116. Tokudome, Y., Imaeda, N., Ikeda, M., Kitagawa, I., Fujiwara, N., Tokudome, S., 1999. Foods contributing to absolute intake and variance in intake of fat, fatty acids and cholesterol in middle-aged Japanese. Journal of Epidemiology 9, 78– 90. UKFSA, 2003. Food Standards Agency, UK. Retrieved June 18, 2008 from: http:// www.food.gov.uk/news/pressreleases/2003/feb/tuna_mercury. USDA, 1998. US Department of Agriculture, Agricultural Research Service. 1989–91 continuing survey of food intakes by individuals and 1989–91 diet and health knowledge survey. Accession number: PB96-501747. USFDA, 2001. Food and Drug Administration, USA. Retrieved June 18, 2008 from: http://vm.cfsan.fda.gov/dms/admehg.html. USFDA, 2004. Food and Drug Administration, USA. Retrieved June 18, 2008 from: http://www.cfsan.fda.gov/dms/admehg3.html. Wakai, K., Ito, Y., Kojima, M., Tokudome, S., Ozasa, K., Inaba, Y., Yagyu, K., Tamakoshi, A., Group, J.S., 2005a. Dietary intakes of fat and fatty acids and risk of breast cancer: a prospective study in Japan. Cancer Science 96, 590–599. Wakai, K., Tamakoshi, K., Date, C., Fukui, M., Suzuki, S., Lin, Y.S., Niwa, Y., Nishio, K., Yatsuya, H., Kondo, T., Tokudome, S., Yamamoto, A., Toyoshima, H., Tamakoshi, A., Group, J.S., 2005b. Intake frequency of fish and serum levels of long-chain n-3 fatty acids: a cross-sectional study within the Japan Collaborative Cohort Study. Journal of Epidemiology 15, 211–218. Yokoo, E., Valente, J., Grattan, L., Schmidt, S.L., Platt, I., Silbergeld, E.K., 2003. Low level methyl mercury exposure affects neuropsychological function in adults. Environmental Health: A Global Access Science Source 200, 8–19. Zahir, F., Rizwi, S.J., Haq, S.K., Khan, R.H., 2005. Low dose mercury toxicity and human health. Environmental Toxicology and Pharmacology 20, 351–360.
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Original Article
Simulated impact of a change in fish consumption on intake of n-3 polyunsaturated fatty acids Ying Zhang a,b,*, Satoshi Nakai a, Shigeki Masunaga a a b
Graduate School of Environment and Information Sciences, Yokohama National University, 79-7 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan School of Environment and Biological Science and Engineering, Dalian University of Technology, No. 2 Linggong Road, Dalian 116024, China
A R T I C L E I N F O
A B S T R A C T
Article history: Received 9 August 2008 Received in revised form 28 January 2009 Accepted 2 March 2009
The objective of this study was to elucidate the impact of a change in fish consumption on the intake of long chain n-3 polyunsaturated fatty acids (LC n-3 PUFA), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) by Japanese women. A probabilistic assessment model for EPA&DHA intake was first proposed to describe the relationship between fish consumption and EPA&DHA intake, and was compared with the survey data. Various scenarios were designed for women representing potential responses to an advisory on fish consumption recently issued in order to avoid risks associated with intake of methyl mercury (MeHg). Elimination of women’s consumption of fish species with high and medium levels of MeHg resulted in a reduction of EPA&DHA intake from 0.85 g/d to 0.82 g/d. The percentage of women with an EPA and DHA intake over 0.25 g/d also decreased from 99.5% to 99.0%. The model results suggested that the changes in fish consumption related to MeHg advisories have a minor influence on the intake of EPA&DHA and on the percentage of women with EPA&DHA intake exceeding the guideline for Japanese women. Nevertheless this simulation could aid the selection of fish species in order to ensure adequate intake of EPA&DHA while minimizing exposure to MeHg. ß 2009 Elsevier Inc. All rights reserved.
Keywords: EPA&DHA n-3 polyunsaturated fatty acids (n-3 PUFA) Intake assessment Fish consumption Japanese women Methyl mercury (MeHg) Food analysis Food composition
1. Introduction Consumption of fish or seafood is important because of its positive effects on human health. Recent studies indicate that an adequate consumption of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the important long chain n-3 polyunsaturated fatty acids (LC n-3 PUFA), can help to protect humans against several adverse health effects, including mortality due to coronary heart disease (CHD), and stroke, as well as cancer. (Bouzan et al., 2005; Colombo et al., 2004; Iso et al., 2006; Kris-Etherton et al., 2002; MacLean et al., 2006; Wakai et al., 2005a). Humans are unable to synthesize EPA and DHA in their body at a sufficient level and, therefore, they must obtain them from their diet. Fish is a rich dietary source of LC n-3 PUFA, especially EPA and DHA. Most of the EPA and DHA found in the human body are derived from fish (Tokudome et al., 1999). Among the LC n-3 PUFA, DHA may be especially critical for the developing brain in uterus (Cohen et al., 2005; Daniels et al., 2004), since the fetus must obtain DHA directly from the mother. Although fish is a rich source of LC n-3 PUFA, it may also contain methyl mercury (MeHg), a neurotoxin that may adversely affect the development of the brain and nervous system. Epidemiological studies in the Faroe Islands, Seychelles, and New Zealand indicate
* Corresponding author. Tel.: +86 411 8470 6251; fax: +86 411 8470 6252. E-mail address: [email protected] (Y. Zhang). 0889-1575/$ – see front matter ß 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.jfca.2009.03.007
that even low-dose chronic exposure to MeHg through fish consumption leads to cognitive developmental delays in children (Myers et al., 2000; Yokoo et al., 2003; Zahir et al., 2005). Moreover, fetuses have been identified as the population most sensitive to MeHg exposure through maternal fish consumption (NRC, 2000). In order to avoid the risk related to MeHg, the US Food and Drug Administration recommends that pregnant women, women who might become pregnant, young children and nursing mothers modify their fish consumption pattern (USFDA, 2001, 2004). This advisory has been taken up in other countries, including Japan (CFIA, 2002; MHLW, 2003a; UKFSA, 2003). Specifically, the advisory issued in Japan (MHLW, 2003a) recommends that women of child-bearing age modify their seafood consumption. The marine species designated in the advisory, such as bottlenose dolphin, whale, blackfish, shark, swordfish and splendid alfonsino, should be reduced to a limited amount, i.e. a consumption pattern of less than once every two weeks, once every month, or once every two months. In 2005, the advisory was revised to include 16 species. Fish consumption incurs both PUFA-related benefits and MeHgrelated risks. Therefore, the advisories issued in order to avoid MeHg-related risk may raise another kind of risk, namely that of lower EPA&DHA intake. To avoid MeHg-related risk, people could either reduce the amount of fish consumed or modify the fish species they consume. However, the impact of these changes on EPA&DHA intake has not been clearly shown. To assess the
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potential impact of the advisory, and to help people understand the impact of these modifications on EPA&DHA intake, we designed a population-based model of EPA&DHA intake and simulated the impact of shifts in fish consumption on EPA&DHA intake for the Japanese population. Our PUFA intake model aimed to describe the relationship between EPA&DHA intake and fish consumption. It was constructed based on fish consumption by individual, species-specific fish market share, and EPA&DHA concentration in fish. Then the estimated EPA&DHA intakes from our proposed model were compared with the reported data from a dietary survey study conducted in Japan (Okuda et al., 2005) as part of the International Study of Macronutrients and Blood Pressure (INTERMAP). Next, the impact of shifts in fish consumption on EPA&DHA intake was estimated only for women by simulating the EPA&DHA intake under various scenarios using the proposed PUFA intake model. A number of scenarios were simulated in order to analyze alternative choices for avoiding the MeHg-related risk from fish consumption, and to describe different patterns of fish consumption that consumers may choose in response to the advisories. 2. Data and methodology
Fish groups
Fish name
Market sharea (%)
EPA&DHAb (mg/g)
Tuna
Yellowfin tuna Bluefin tuna Albacore tuna Southern bluefin Bigeye tuna Other tuna
33.8 3.4 19.2 1.9 35.0 6.7
0.75 1.47–46 1.87 0.09–40 2.3 11.6
Seabream and Flat fish
Red seabream Porgy Black seabream Flounder Flatfish
46.2 3.8 2.3 40.0 7.6
9.1–18.7 4.4 6.7 1.64–11.8 4.1–6.7
a Market share was estimated from the domestic fish catch amounts (MAFF, 1995). b EPA&DHA data were adopted from the standard tables of food composition (fifth revised and enlarged edition, fatty acids section) MEXT (2005). EPA&DHA concentration is given as a range, when more than one EPA&DHA level provided in the database (MEXT, 2005); EPA&DHA concentration is given as one value, while only one value of EPA&DHA level provided in the database.
based on the data taken from the U.S. Department of Agriculture Continuing Survey of Food Intake by Individuals (CSFII) (USDA, 1998). These data were kindly provided by Dr. Carrington from USFDA, one of the authors of Carrington and Bolger (2002).
2.1. PUFA intake model 2.1.1. Species-specific fish consumption Fish consumption data for Japanese individuals were adopted from the Health and Nutrition Information Infrastructure Database System (HNIIDS, 1995) by National Institute of Health and Nutrition, which was constructed based on the National Nutrition Survey (NNS, 1995) in Japan. The NNS is carried out using a questionnaire on a day in the month of November every year, and the respondents are required to perform 24-h recall. The NNS is the representative diet and nutrient survey in Japan. More than 15,000 respondents are involved in the NNS, and over 95% of the consumers reported their fish consumption. In the HNIID database, the fish consumed were not given as the fish species directly consumed in the one-day record by each respondent, but reported as mean value and standard deviation (S.D.) of 13 fish groups for various population groups (i.e. children (1–6 years), women, men and total population). The mean and S.D. were reported based on the cumulative statistics for only those individuals who reported consumption of seafood on the survey day, according to the questionnaires of the one-day diet record. In order to capture the variability of EPA&DHA intake from each species, the concentration of EPA&DHA in the various fish species had to be considered. However, the EPA&DHA concentrations differed considerably within the 13 fish groups reported in the HNIID database. Thus, the market-weight shares within each fish group were used to divide 13 fish groups into 58 fish species groups. The market-weight shares within each group were estimated for each species based on the weight of domestic catches reported by the Ministry of Agriculture, Forestry and Fisheries of Japan (MAFF, 1995) (examples listed in Table 1). Thus, species-specific fish consumption by an individual was estimated based on the reported fish consumed by the individual and species-specific market share of fish, using the following formula: Mi ¼ M j F k j
Table 1 Examples of market share and EPA&DHA level in some fish species.
2.1.2. PUFA levels in fish The EPA&DHA level in each species depends heavily on the preparation methods, e.g. raw, steamed, or fried (MEXT, 2005). The range (minimum to maximum) of EPA&DHA level for each species prepared in different ways was taken from the Standard Tables of Food Composition (Edition 5), issued by Ministry of Education, Culture, Sports, Science, and Technology of Japan (MEXT, 2005). Some examples of EPA&DH levels in fish species are given in Table 1. Since the relevant data are difficult to collect, the distribution of EPA&DHA level in each fish species has been difficult to describe until now, therefore, the distribution of EPA&DHA levels in each fish species was assumed to be uniform simply. 2.1.3. Estimating PUFA intake Daily individual PUFA intake was estimated using the following formula: X D¼ ðC i M i Þ (2) i
where D is the daily PUFA intake; i is fish species; Ci is PUFAs level in the ith fish species; and Mi is the consumption of the ith fish species.
(1)
where Mi is an individual’s intake of fish of the ith species; Mj is the daily intake of fish of the jth group; and Fkj isX the market share of 13 kth fish species in jth fish group (j = 13, i ¼ k j ¼ 58). The distribution of the fish consumed j¼1 was assumed to be lognormal, similar to the fish consumption pattern reported for Americans (Fig. 1) according to the likelihood empirically. Fig. 1 is
Fig. 1. Daily fish consumption pattern of Americans.
Y. Zhang et al. / Journal of Food Composition and Analysis 22 (2009) 657–662
The distribution of PUFA intake among population was simulated using Crystal Ball1 with Monte Carlo simulation. Specifically, Crystal Ball1 was used to estimate the output by combining randomly sampled amounts of fish species consumed by an individual with PUFA concentration in each fish species. These samples were generated randomly from two database sets: (i) the distribution of consumed fish and (ii) the distribution of PUFA levels in these fish species. The sampling process was repeated 100,000 times, which was considered to sufficiently represent the variability of the PUFA intake, for each sex and age group. 2.2. Scenarios To simulate the influence of different risk management options on EPA&DHA intake, some hypothetical scenarios were designed to represent potential consumer responses to the advisory. The scenarios considered changes in both choice of fish species and amounts of each fish species consumed, assuming that these changes would be completely accurate throughout the entire fish market. The impact of changes in fish consumption on the EPA&DHA intake under these scenarios was simulated for only women, since women are the primary target population of the advisory. Scenario 0 corresponds to the baseline (no changes in response to the advisory). Scenario 1 is somewhat less optimistic. The advisory issued in Japan recommends that women of child-bearing age avoid consuming fish species with high MeHg concentration. In this
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scenario, women were assumed to misinterpret the advisory, such that they decreased their total fish consumption by 12% but did not change the fish species consumed. This extent of reduction in fish consumption was assumed to be at the same extent across all fish species, and was applied based on the fact that total amount of fish consumption has reported decreased by approximately 12% following the issuance of the advisory issued in 2003 (MHLW, 2003b). It was impossible to say with certainty whether the 12% reduction was due entirely to the advisory; nevertheless, this reduction served to indicate potential changes in consumption. Scenario 2 corresponds to an optimistic response to the advisory. In the advisory, fish were categorized into three groups based on their concentration of MeHg: high (MeHg concentration >0.4 mg/g), medium (MeHg concentration of 0.14–0.4 mg/g), and low (MeHg concentration <0.14 mg/g) (Table 2). This scenario assumes that only low-MeHg fish were consumed by women of child-bearing age, which leads to a reduction in overall fish consumption. Scenario 3 is similar to scenario 2, but differs in that only highMeHg fish species were eliminated by women. Scenario 4 represents the ideal response to the advisory. In addition to not consuming high- or medium-MeHg fish, women maintained the same overall amount of fish consumption by increasing their consumption of low-MeHg fish. This scenario was considered more optimistic than scenario 2, because it allowed for women to maintain their pre-advisory LC n-3 PUFA intake. Scenario 5 describes a response opposite to that of scenario 1. Under this scenario, women increased their overall fish consumption by 12%, assuming that they completely relied on the health
Table 2 EPA&DHA and MeHg concentrations in some fish species. Groups based on the advisory
Fish species
MeHga (mean, mg/g)
High
Swordfish Bigeye tuna Bluefin tuna Southern bluefin
0.67 0.57 0.54 0.40
6.4 2.3 1.47–46 0.09–40
Medium
Shark Marlin Porgy Other tuna Perch Black seabream Yellowtail Tilefish Snow crab Blue marlin Yellowfin tuna Albacore tuna
0.36 0.35 0.33 0.31 0.27 0.21 0.20 0.20 0.19 0.19 0.18 0.16
0.59–11.2 3.71 4.4 11.6 4.5 6.7 26.4–29 4.2–5.9 0.73–1.5 0.4 0.75 1.87
Low
Red seabream Frigate mackerel Skipjack Canned tuna Flatfish Sand lance Mackerel Sea bass Cod roe Alaska pollock Atka mackerel Cutlass fish Cod & Hake Sardine Eel Trout
0.13 0.13 0.12 0.11 0.08 0.08 0.07 0.07 0.07 0.06 0.06 0.05 0.05 0.05 0.05 0.05
9.1–18.7 6.5 1.12–13.7 0.79–5.5 4.1–6.7 9.5–14.2 12–44 7 9.5–14.3 0.58–1.14 8.3–9.8 23.7 0.56–1.74 9.5–9.7 16.1–20.5 6.9–21.9
a
EPA&DHAb (mg/g)
DHAb (mg/g) 5.3 1.9 1.2–32 0.07–27 0.5–6.9 3.1 3.3 8.5 2.5 4.1 17–19 2.7–3.9 0.33–0.5 0.36 0.65 1.5 8.9–11 4.7 0.88–9.7 0.65–4.4 2.9–4.5 5–7.7 7–27 4 5–7.8 0.34–0.67 3.5–5.3 14 0.42–1.1 6.6 0.47–13 4.9–14
MeHg data were adopted from the MeHg levels in fish (MHLW, 2004). EPA&DHA data were adopted from the standard tables of food composition (fifth revised and enlarged edition, fatty acids section) (MEXT, 2005). The groups based on the advisory: high means MeHg level in fish over 0.4 mg/g; medium means MeHg level between 0.14 and 0.4 mg/g, and low means MeHg level below 0.14 mg/g. EPA&DHA concentration is given as a range, when more than one levels are available in the database (MEXT, 2005); EPA&DHA concentration is given as one value, while only one value of level available in the database. b
Y. Zhang et al. / Journal of Food Composition and Analysis 22 (2009) 657–662
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3.2. Daily PUFA intake for women under different scenarios
Table 3 EPA&DHA intake from fish consumption for Japanese population. Percentile (g/day)
Women
Men
Total
Mean 2.5th 5th Median 90th Percentage >0.25 g/d
0.85 0.31 0.35 0.70 1.81 99.5%
1.02 0.38 0.43 0.85 2.15 99.9%
0.93 0.35 0.39 0.70 1.81 99.8%
Table 4 Comparison of n-3 PUFA intake between INTERMAP study and this study. n-3 PUFA (g/day)
Data
Women, mean (S.D.)
Men, mean (S.D.)
EPA&DHA
This study INTERMAP (Okuda et al., 2005)
0.85 (0.70) 0.88 (0.56)
1.02 (0.77) 1.20 (0.73)
This study INTERMAP (Okuda et al., 2005)
0.51 (0.38) 0.56 (0.33)
0.62 (0.47) 0.75 (0.43)
DHA
Note: Women and men referred belonged to all age segments in life span in this study; while women and men aged 40–59 years were involved in Okuda et al. (2005).
benefits, but regardless of the health risk related to fish consumption. 3. Results 3.1. Estimated results of PUFA intake Utilizing the proposed intake model, EPA&DHA and DHA intakes were estimated for all Japanese as well as for women and men. The estimated results with mean, median and several percentiles are given in Table 3. The mean value of EPA&DHA intake for women is 0.85 g/d, with a median of 0.70 g/d and 90th percentile of 1.81 g/d. Okuda et al. (2005) conducted a dietary survey in Japan (n = 572 men and 570 women), within the context of the International Study of Macronutrients and Blood Pressure (INTERMAP), which was one of the largest studies on daily PUFA intake in Japan. In their study, the n-3 PUFA intakes for men and women aged 40–59 years were reported with means and standard deviations (see Table 2 in Okuda et al., 2005). We applied their results to compare with our estimations. Table 4 illustrates the comparison of the two studies, and it shows that our results are somewhat underestimated compared with those of the INTERMAP study.
The proposed intake model was utilized to estimate EPA&DHA intake under various scenarios. Table 5 gives the simulated results for each scenario, expressed in terms of EPA&DHA intake, as well as the percentage of population achieving or exceeding the guideline. The results illustrate that eliminating fish species with high- and medium-MeHg levels resulted in the reduction of EPA&DHA intake from 0.85 g/d to 0.82 g/d (from baseline to scenario 2). When the eliminated amounts of high- and medium-MeHg fish were compensated for by increasing consumption of other fish species, EPA&DHA intake increased from 0.82 g/d to 0.89 g/d (from scenario 2 to scenario 4). 4. Discussion The primary motivation of this study was to demonstrate the impact of changes in fish consumption on EPA&DHA intake among Japanese women. A probabilistic PUFA intake model was proposed to provide an analytical tool that relates EPA&DHA intake to fish consumption. Our estimations were somewhat underestimated for both women and men compared to the survey data from Okuda et al. (2005); however, the similarity of our model’s results with those of the INTERMAP study suggests that the model is satisfactory for simulating the PUFA intake from fish consumption (see Table 4). The intake of n-3 PUFA was illustrated to protect humans against several adverse health effects, e.g. heart diseases and stroke. Accordingly, a number of countries and organizations have made formal, population-based dietary recommendations on LC n-3 PUFA intake. In Japan, the dietary reference intake on LC n-3 PUFA was issued, but not on EPA&DHA, where LC n-3 PUFA refer to C18:3, C18:4, C20:4, C20:5 (EPA), C21:5, C22:5 and C22:6 (DHA). In this issue, the adequate dietary intake of LC n-3 PUFA for women (above 6 years) was recommended to be more than 2.2 g/d (MHLW, 2005). Typical recommendations are 0.3– 0.5 g/d of EPA&DHA for healthy people (Kris-Etherton et al., 2002). The meta-analysis of Mozaffarian and Rimm (2006) found that an average daily intake of 250 mg of EPA&DHA was sufficient for optimal protection against heart attacks. Since there is no guideline on EPA&DHA intake in Japan, we applied the recommendation of 250 mg/d of EPA&DHA intake as the guideline to Japanese. Our simulations showed that 99.8% of the Japanese population consume more than 0.25 g/d of EPA&DHA at the baseline (Table 3), indicating that nearly all Japanese people consumed an adequate amount of EPA&DHA, defined as 0.25 g/d, through fish consumption.
Table 5 EPA&DHA intake for Japanese women under various scenarios. Scenario
0 1 2 3 4 5
Mean fish consumption (g/d)
88.2 77.6 81.1 85.5 88.2 98.8
(EPH + DHA) intake (g/d) Mean
2.5th percentile
5th percentile
Median
95th percentile
0.85 0.75 0.82 0.83 0.89 0.95
0.31 0.28 0.29 0.30 0.31 0.35
0.35 0.31 0.33 0.33 0.35 0.39
0.70 0.61 0.67 0.68 0.73 0.78
1.80 1.58 1.77 1.80 1.93 2.02
Note: Women referred belonged to all age segments in the life span. Scenario 0: represents baseline. Scenario 1: fish consumption decreased by 12%. Scenario 2: only fish with low MeHg (<0.14 mg/g) consumed. Scenario 3: fish with high MeHg (>0.4 mg/g) avoided to consume. Scenario 4: fish with low MeHg (<0.14 mg/g) consumed, and the overall consumption amount maintained by increasing low-MeHg fish. Scenario 5: fish consumption increased by 12%.
Percentage of EPA&DHA >0.25 g/d (%) 99.5 98.7 99.0 99.2 99.4 99.8
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To reduce MeHg exposure by simply reducing the amount of highMeHg fish can lead to a reduction in EPA&DHA intake. Eliminating the high- and medium-MeHg fish species, resulting in the reduction of overall fish consumption, led to decreased EPA + DHA intake by women from 0.85 g/d in the baseline to 0.82 g/d in scenario 2 (Table 5). It illustrated that the changes in consumption related to MeHg advisories have a minor influence on the intake of EPA&DHA. This is because few of the fish species that recorded high levels of EPA&DHA also had high MeHg levels. Such that avoiding intake of fish species with high MeHg levels did not necessarily eliminate high EPA&DHA containing fish species. However, when the overall fish consumption was maintained by increasing the consumption of fish species with a low level of MeHg, EPA + DHA intake increases from 0.82 g/d in scenario 2 to 0.89 g/d in scenario 4. It suggested that EPA&DHA intake could be reconverted by maintaining overall fish consumption. In addition, people could increase their EPA&DHA intake by selecting fish species low in MeHg and high in EPA&DHA. As shown in Fig. 2, the fish species located at the upper left are preferred. There are two methods to avoid MeHgrelated risk: one is to reduce overall fish consumption, and the other is to eliminate consumption of high- or medium-MeHg fish species. The simulated results showed that a greater percentage of Japanese women took in more EPA&DHA than what the guideline prescribed when more fish was consumed. This comparatively higher EPA&DHA intake seemed to be correlated with greater fish consumption. This suggests that the strategy to reduce MeHg exposure by reducing the amount of fish consumption has a greater impact on PUFA intake than the strategy to change the fish species consumed. However, relations between MeHg and EPA&DHA concentrations in seafood may be different depending on countries, thus present results may be specific for Japanese women. The simulated results under various scenarios showed that the percentages of women with over 0.25 g/d EPA + DHA intake changed with the change of fish consumption. However, the percentage of women with over 0.25 g/d EPA + DHA intake in each scenario were still more than 99% (except scenario 1), which suggests that the elimination of consumption of fish species with high and/or medium levels of MeHg has quite limited effect on the EPA&DHA intake. This impact may be explained by the fact that the overall amount of fish consumption by Japanese population is very large, while fish species with high MeHg concentration might not necessarily contain high EPA&DHA concentration.
Fig. 2. MeHg and (EPA + DHA) concentrations in some fish species.
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EPA&DHA intake was estimated from fish consumption in this analysis. However, it should be noted that EPA&DHA could also be obtained from other sources of food, such as eggs, meats, and milk. Mahaffey et al. (2008) noted that fish consumption accounted for the majority of the intake of EPA + DHA. Similarly, it has been suggested that fish are the main source of DHA for Japanese individuals, and that fish intake explains more than 90% of the inter-individual variation in EPA intake (Tokudome et al., 1999). These findings indicate that changes in fish consumption can cause changes in EPA&DHA intake. In addition to estimating the dietary EPA&DHA intake, it would also be useful to estimate the body (blood or serum) levels of EPA&DHA. This is because the body EPA&DHA levels would be directly related to the derived health benefits. The dietary EPA&DHA intake from fish consumption was reported to be related to the body (blood or serum) levels for the Japanese (Kuriki et al., 2003; Kobayashi et al., 2003; Wakai et al., 2005b). However, the quantitative relationship between them is not available; hence we could not estimate the body levels from the dietary EPA&DHA intake. We compared our estimations using the proposed model with the empirical data from the INTERMAP study, which showed that our estimations were comparatively lower. This may be explained from several respects. The age ranges of participants were different for the two studies: the subjects recruited in INTERMAP study were aged 40–59 years, while women of all age segments of life span were recruited in this present study. In addition, some assumptions presently made for the purpose of this EPA&DHA intake assessment may also cause some errors in our results, such as the market share and distribution patterns of PUFA. The market share of each fish species was calculated based on the domestic fish catch amounts reported by MAFF, though only half of the fish consumed were caught domestically (MAFF, 1995). Therefore, taking the import portion of fish into consideration may improve the intake assessment. The distribution of EPA&DHA levels in each fish species was simply assumed to be uniform. Sioen et al. (2007) constructed a nutrient database based on 14 food composition databases from various countries. The fish species consumed by the Japanese were focused in this study, so we did not apply their database. However, better selection of distribution patterns may improve the resulting estimations. Moreover, the consumption data used were adopted from the survey in 1995, which were the only one available for the public until now although they were rather old. The estimation would be updated as the fish consumption got updated in the future. It should be noted that there are some other contaminants present in seafood, e.g. dioxins-like compounds, polychlorinated biphenyls, and other heavy metals (As, Pb, etc.). MeHg was focused on in this analysis in view of the fact that fish is the most important dietary source of mercury in the human diet. Additionally, changes in fish consumption would possibly influence the exposure to other contaminants, although it was not taken into account here. Sioen et al. (2008a,b) have presented the relation between dioxin exposure and EPA&DHA intake from fish consumption. Considering the fish consumption associated health benefits, the hazards from other contaminants should also be taken into account. Since survey data are probably more reliable than the derived predictions from a simulation, the purpose of this simulated intake assessment was much of one that could provide an analysis tool to relate EPA&DHA intake with fish consumption and EPA&DHA level in fish across the Japanese population. This EPA&DHA intake model is considered to be useful in simulating the changes in EPA&DHA intake when fish consumption changes. The results of this analysis may be expanded to predict the change in health benefits when combined with dose–response relationships. Essentially, this analysis may be particularly useful as part of risk-benefit analysis.
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5. Conclusions To reduce MeHg exposure by simply reducing the amount of high-MeHg fish could lead to a reduction in EPA&DHA intake, which was demonstrated quantitatively using the developed assessment model and designed scenarios for women. Eliminating fish species with high and medium levels of MeHg led to a quite limited reduction of the EPA&DHA intake among Japanese women population. While avoiding the risk associated with MeHg from fish consumption, the EPA&DHA intake could be maintained by maintaining the overall fish consumption or selecting fish species low in MeHg and high in EPA&DHA. Additional attention should be paid to the exposure to other contaminants, e.g. dioxins and polychlorinated biphenyls, which would also be changed along with the fish consumption. Nevertheless, this simulation has the potential to aid the selection of fish species in order to ensure adequate intake of EPA&DHA while minimizing exposure to MeHg, and may be particularly useful as part of risk-benefit analysis. Acknowledgements The authors thank the anonymous reviewers for their constructive comments and suggestions. Thanks from the authors also to Mr. Jonathan N. Hogarh, and Dr. Vasu Tiwari, both of Yokohama National University for their constructive comments on our manuscript. References Bouzan, C., Cohen, J.T., Connor, W.E., Kris-Etherton, P.M., Gray, G.M., Konig, A., Lawrence, R.S., Savitz, D.A., Teutsch, S.M., 2005. A quantitative analysis of fish consumption and stroke risk. American Journal of Preventive Medicine 29, 347–352. Carrington, C.D., Bolger, P.M., 2002. An exposure assessment for methyl mercury from seafood for consumers in the United States. Risk Analysis 22, 689–699. CFIA, 2002. Food Inspection Agency, Canada. Retrieved June 18, 2008 from: http:// www.inspection.gc.ca/english/fssa/concen/specif/mercury.shtml. Cohen, J.T., Bellinger, D.C., Connor, W.E., Shaywitz, B.A., 2005. A quantitative analysis of prenatal intake of n-3 polyunsaturated fatty acids and cognitive development. American Journal of Preventive Medicine 29, 366–374. Colombo, J., Kannass, K.N., Shaddy, D.J., Kundurthi, S., Maikranz, J.M., Anderson, C.J., Blaga, O.M., Carlson, S.E., 2004. Maternal DHA and the development of attention in infancy and toddlerhood. Child Development 75, 1254–1267. Crystal Ball1, 2000. Decisioneering, professional edition, Japanese version. Daniels, J.L., Longnecker, M.P., Rowland, A.S., Golding, J., ALSPAC Study Team, 2004. Fish intake during pregnancy and early cognitive development of offspring. Epidemiology 15, 394–402. HNIIDS, 1995. Health and Nutrition Information Infrastructure Database System. Retrieved November 18, 2006 from: http://www.nih.go.jp:888 (being locked now due to some reasons, in Japanese). Iso, H., Kobayashi, M., Ishihara, J., Sasaki, S., Okada, K., Kita, Y., Kokubo, Y., Tsugane, S., JPHC Study Group, 2006. Intake of fish and n-3 fatty acids and risk of coronary heart disease among Japanese. Circulation 113, 195–202. Kobayashi, M., Sasaki, S., Kawabata, T., Hasegawa, K., Tsugane, S., 2003. Validity of a self-administered food frequency questionnaire used in the 5-year follow-up survey of the JPHC Study Cohort I to assess fatty acid intake: comparison with dietary records and serum phospholipid level. Journal of Epidemiology 13 (1 Suppl.), s64–s81. Kris-Etherton, P.M., Harris, W.S., Appel, L.J., 2002. Fish consumption, fish oil, omega3 fatty acids, and cardiovascular disease. Circulation 106, 2747–2757. Kuriki, K., Nagaya, T., Tokudome, Y., Imaeda, N., Fujiwara, N., Sato, J., Goto, C., Ikeda, M., Maki, S., Tajima, K., Tokudome, S., 2003. Plasma concentrations of (n-3) highly unsaturated fatty acids are good biomarkers of relative dietary fatty acid intakes: a cross-sectional study. The Journal of Nutrition 133 (11), 3643–3650. MacLean, C.H., Newberry, S.J., Mojica, W.A., Khanna, P., Issa, A.M., Suttorp, M.J., Lim, Y.-W., Traina, S.B., Hilton, L., Garland, R., Morton, S.C., 2006. Effects of omega-3 fatty acids on cancer risk: a systematic review. Journal of the American Medical Association 295, 403–415.
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