Knowledge of dietary supplement label information among female supplement users

Patient Education and Counseling 52 (2004) 291–296

Knowledge of dietary supplement label information among female supplement users Carla K. Miller a,∗ , Teri Russell b a

Department of Nutritional Sciences, Pennsylvania State University, 12 Henderson Building, University Park, PA 16802, USA b Graduate Program in Nutrition, University of North Carolina at Greensboro, Greensboro, NC, USA Received 5 August 2002; received in revised form 8 January 2003; accepted 17 January 2003

Abstract The use of dietary supplements is a popular form of health behavior, especially among women. Little research has been conducted to determine consumers’ comprehension of supplement label information. Therefore, this research evaluated comprehension of supplement label information among women 25–45 years of age who consumed a dietary supplement ≥4 times per week. Participants (n = 51) completed a written questionnaire about supplement practices, a 10-item knowledge test, and an individual interview about terms used on supplement labels. Participants answered 70% of the questions correctly on the knowledge test indicating adequate knowledge of dietary sources of nutrients. Knowledge of recommended dosages, dosing instructions, and instructions about inappropriate use of supplements for certain people also was adequate. However, misconceptions regarding the term “natural” on supplement labels, product claims, and testing for product safety existed among participants. Supplement users need additional education about supplement claims and testing for product safety and efficacy to make informed health care choices. © 2003 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Dietary supplements; Knowledge; Health promotion; Labeling

1. Introduction The prevalent use of dietary supplements is one of the most striking events that occurred in health behavior in the US in recent years. Estimates of prevalence of vitamin and mineral supplement intake range from 40% in recent national surveys to >60% in specialized populations [1–6]. The most commonly used supplements are vitamin, mineral, and herbal preparations [7]. Supplement users reported out-of-pocket expenditures of US$ 3.3 billion in 1997 for high-dose vitamin supplements and US$ 5.1 billion for herbal products [8]. Higher rates of adult vitamin and mineral supplement use are consistently reported among women, the better educated, and the more affluent [1,9–13]. Supplement users report taking supplements to maintain health, prevent disease, and “feel better” [14–16]. The Dietary Supplement Health and Education Act (DSHEA) was passed by Congress in 1994. Under DSHEA, supplements must be safe under the conditions recommended on the label, or, if no conditions of use are given,

∗ Corresponding author. Tel.: +1-814-865-4479; fax: +1-814-865-5870. E-mail address: [email protected] (C.K. Miller).

under ordinary conditions of use [17]. The responsibility for safety of the supplement is placed on the manufacturer or marketer of the substance, not the Food and Drug Administration (FDA). DSHEA also regulates the use of statements of ingredients, statements of nutritional support or structure/function claims (e.g. ginkgo helps increase blood circulation to the brain), and nutrient content claims (e.g. “high,” “low,” or a “good source” of a supplement) [18]. Statements of nutritional support may be added to a supplement label as long as: (1) the manufacturer has substantiation that such a statement is truthful and not misleading; and (2) the label displays the disclaimer that “This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease” [18]. In enacting DSHEA, Congress indicated that supplements should be available in the marketplace to consumers, and consumers should be able to make informed and appropriate health care choices [17]. Women of childbearing age often make decisions regarding supplement use for themselves and their families. However, little research has been reported regarding women’s knowledge and understanding of information found on supplement labels such as statements of nutritional support and product safety. Whether supplement

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users accurately interpret the information on supplement labels to make informed health care choices has received little investigation. Survey and questionnaire research can provide information about consumers’ attitudes, beliefs, and health practices. However, closed-ended survey questions limit the responses consumers can offer to those included on the survey and fail to explain why a specific response was chosen. In contrast, open-ended interview questions allow consumers to answer questions in their own words. One-on-one interviews are the most penetrating method for assessing a person’s knowledge and problem solving ability [19]. Thus, an integration of closed-ended survey questions and open-ended interview questions can provide a comprehensive assessment of consumers’ knowledge of and practices in a given domain. The purpose of this study was to identify supplement users’ beliefs and knowledge about information found on supplement labels and knowledge of dietary sources of nutrients. Women of childbearing age were recruited since women in this age group are frequent users of dietary supplements [5,6,9]. Both survey and interview methodologies were used. The information gained from this research can enable educators to develop appropriate and effective targeted messages about supplement use for this audience.

2. Materials and methods Women 25–45 years of age in an urban community who consumed a dietary supplement at least four times per week were eligible for the study. Women who were pregnant or lactating or planning on becoming pregnant or lactacting were excluded since prenatal vitamins are recommended for these women. Recruitment included advertisements in local newspapers and a college newspaper and at gynecology and family practice medical offices, hair salons, and health clubs. The study was advertised as a general consumer research study instead of a nutrition study to reduce social desirability effects. People who responded to recruitment notices were screened for eligibility through a telephone interview. Questions regarding age, supplement use, and intention to become pregnant or breastfeed were included during the screening process. All eligible and interested participants were mailed a written questionnaire to complete at their convenience. The questionnaire included items regarding supplement use, demographic characteristics of the sample, and 10 multiple choice knowledge questions about dietary sources of nutrients and dietary supplements. Six of the questions on the knowledge test listed food items, and participants were asked to select the food that was the best source of a nutrient (e.g. best source of vitamin E). Three questions on the knowledge test assessed participants’ knowledge of nutrients for health conditions (e.g. iron

Fig. 1. Interview questions administered to each participant.

needed to prevent anemia). One question asked participants to select the supplement that was an antioxidant. Then, each participant completed an individual, face-toface interview about the information found on dietary supplement labels (see Fig. 1 for the interview questions). Bottles of St. John’s wort and echinacea were used as props during the interview. The interview was audio recorded for later analysis. Field notes were made following each interview to record pertinent observations and comments made by participants. All methods were approved by the Institutional Review Board at the sponsoring university and participants provided informed consent. Each person received a small honorarium upon study completion. Analyses of the written questionnaire and oral interviews were conducted. Frequency distributions and means were calculated for data from the written questionnaire using JMP statistical analysis software (version 4, 2001, SAS Institute Inc., Cary, NC). Analysis of the interviews included transcribing the audiotapes of the interviews verbatim. A summary was written for each answer provided by each participant. The investigators reviewed and discussed the field notes, transcripts, and summary statements to identify common themes and response categories for each interview question. Participants’ response to each question was assigned to the appropriate category; however, some responses could not be assigned to a category due to an ambiguous or “don’t know” response. Direct quotes of participants’ responses to interview questions are provided below to illustrate participants’ knowledge and beliefs regarding dietary supplements.

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293

Table 1 Demographic characteristics of study participants (n = 51)

3. Results

Mean ± S.D.

3.1. Participant characteristics and supplement use Sixty-one women responded to recruitment notices and were screened for study eligibility. Nine women did not meet the eligibility criteria for the study and one person failed to complete the interview. Therefore, complete data were available for 51 women. The mean ± standard deviation (S.D.) age of the sample was 36.0 ± 6.0 years (Table 1). Seventy five percent of the sample had a college education. The majority of the sample was Caucasian (84.3%) and employed on a full-time basis outside the home (54.9%). Table 2 includes the five most frequently consumed supplements by study participants. About half of the sample consumed Vitamin C, calcium and a One A Day® multivitamin. Of those who took these supplements, most consumed the supplement on a daily basis. In contrast, 66.7% of participants who used echinacea reported taking echinacea less than once per week and only when experiencing symptoms of a cold. The majority (60.8%) of participants reported taking supplements to prevent an illness (Table 3). Participants purchased supplements primarily in drugstores (60.8%) or health food stores (56.9%). Average monthly expenses for supplements ranged from US$ 40 per month (20%) (Table 3). The mean ±S.D. number of questions correct on the knowledge test was 7.0 ± 1.7 out of 10 possible points. 3.2. Knowledge about ingredients, use, and dosing instructions on supplement labels Three questions included during the individual interviews assessed participants’ ability to accurately determine specific information from supplement labels. A bottle of St. John’s wort was provided. Participants were asked to name the active ingredient in St. John’s wort, identify the recommended dose for the supplement, and explain the instructions about who should avoid taking the product according to information on the label. Analysis of the interview questions revealed only 54.2% of the participants correctly named the active ingredient in St. John’s wort. Most (76.7%) of the participants identified the recommended dose of a supplement. Almost all (98.0%) of the participants correctly stated those who should not take the supplement according to the label.

Age (years) Body mass index (kg/m2 )a

36.0 ± 6.0 24.4 ± 4.7 n

%

Education ≤12th grade Some college Bachelor’s degree Advanced degree

2 11 23 15

3.9 21.6 45.1 29.4

Employment Full-time (≥32 h per week) Part-time (<32 h per week) Full-time student Full-time homemaker Unemployed

28 8 5 9 1

54.9 15.7 9.8 17.6 2.0

Race/ethnicity Caucasian African American Asian American Native American Hispanic

43 4 2 1 1

84.3 7.8 3.9 2.0 2.0

Household composition Lives with spouse only Lives with children only Lives with spouse & children Lives with someone other than spouse Lives alone

14 4 18 4 11

27.5 7.8 35.3 7.8 21.6

Household incomeb
7 3 5 9 5 5 15

14.3 6.1 10.2 18.4 10.2 10.2 30.6

a b

Values are based on self-reported data for height and weight. Two people did not provide data for this item.

3.3. Knowledge about the percent daily value Participants were queried during the interview about the meaning of the percent daily value on the label. Fourteen percent confused the daily value with the recommended dietary allowance (RDA) previously used on food labels. One person said, “I thought it meant recommended daily amount

Table 2 Five most frequently consumed supplements among study participants and their frequency of consumption Supplement

Vitamin C One A Day® multivitamin Calcium Echinacea Vitamin E

Sample consuming (%)

51 43 43 37 27

Frequency of consumption (%) <1 per week

1–3 per week

4–6 per week

1 per day

≥2 per day

16.0 0.0 4.5 66.7 0.0

12.0 9.1 9.1 11.1 7.1

20.0 31.8 13.6 0.0 28.6

28.0 45.5 36.4 5.6 28.6

24.0 13.6 36.4 16.7 35.7

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Table 3 Measures related to dietary supplement use among study participants (n = 51) Supplement characteristic

%

Reasons for taking a supplement Prevent an illness Feel lack of energy Recommended by family or friend Treat an illness Advertisement

60.8 54.9 31.4 27.5 13.7

Sources of information about supplements Health food store Magazine Health book Friend Family member Physician Co-worker Television Dietitian/nutritionist Other health care professional Radio

72.5 64.7 60.8 47.1 43.1 39.2 23.5 19.6 15.7 13.7 9.8

Places of purchase for supplements Drugstore or pharmacy Health food store Grocery store Mail order Direct sales

60.8 56.9 35.3 19.6 7.8

Use of supplements by members of householda Spouse or partner Children Self only Parent Other family member

48.0 30.0 24.0 22.0 10.0

Average monthly expense for supplementsa ≤US$ 10.00 US$ 11.00–20.00 US$ 21.00–30.00 US$ 31.00–40.00 >US$ 40.00

28.0 22.0 18.0 12.0 20.0

a

One person did not provide data for this item.

or RDA.” Six percent of the sample believed the amount was based on the amount needed for a 2000 kcal diet. However, most participants (65%) believed the daily value was a guideline for the quantity of the supplement needed per day. Of these, 27% believed the guideline was established by scientists or a regulatory agency. “It’s the recommended amount you should take” as one person stated. Another person said, “It means that some scientists somewhere for the government have determined how much of this I absolutely need.” Participants were shown a bottle for an herbal supplement and asked to describe their understanding of the term “not established” under the percent daily value heading on the supplement label. Many participants (43%) believed that “not established” meant experts did not know whether the supplement was required by or would be beneficial to the body. Thirty one percent thought the term meant scientists did not know the quantity of the herbal required. As one per-

son said, “Those same people who work in that field don’t know what is needed for our bodies on a daily basis. They can’t give us an amount.” The lack of research regarding herbal supplements was expressed by six people. “They’re not quite sure what we need and it hasn’t been researched up to snuff yet so you would take it at your own risk.” 3.4. Knowledge about product claims Participants were shown a bottle of echinacea. On the front of the bottle, the following structure/function claim was included: “Echinacea helps support healthy immune function and promotes general well-being especially during the cold and flu season.” The majority (77%) of the participants stated that echinacea helped prevent a cold, illness or disease. As one person summarized, “With a healthy immune system you’re less likely to take a cold or get sick in the first place.” Nine percent said echinacea reduced the symptoms of a cold. As part of their response, some participants described the function of the immune system. “My feeling is that if it’s helping your immune system, it’s helping your body fight the radical guys that are in the bloodstream. It boosts the production of the good guys that fight the bad guys that are invading. I think the claim is to boost what would normally be produced in your body anyway.” Another person said, “Immune to me is our body’s ability to fight off bacteria, viruses, free floating things you get from the people you work with.” Participants also were asked to explain the disclaimer, which appeared under the claim about immune function on the echinacea bottle: “These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.” Forty percent of participants believed that products with the disclaimer may or may not be beneficial to one’s health because insufficient evidence was available to prove potential benefits claimed by the manufacturer. One person said, “Right now there’s not sufficiently high enough level of scientific proof that this is a needed or valued nutritional substance.” Another 33% of participants thought the statement meant the product was not approved or regulated by the FDA. Some participants (18%) believed that FDA included the statement on the supplement label to protect them from legal action. “It’s a waiver so they don’t get sued for anything,” stated another person. 3.5. Knowledge about product quality During the interview, participants were asked to explain the meaning of the term “natural” used by the manufacturer on supplement labels to describe the product. Twenty five percent of participants thought natural meant the product was derived directly from a plant rather than produced synthetically. One person stated, “It should be based from a plant which includes leaves or roots.” Forty eight percent of the sample said a natural product did not contain additives,

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preservatives, or processed chemicals manufactured in a laboratory. “It doesn’t have a lot of the added preservatives, yeast, soy, artificial flavors and colors, and things like that,” said another person. Three participants were not convinced that a natural product was more beneficial. “It doesn’t necessarily mean that it’s good for you. . . . Cyanide is natural, but that doesn’t mean you want to eat it,” commented one person. Thirteen percent of participants believed the term “natural” was placed on labels for marketing purposes only. “Well, I think that’s a buzz word. They want you to think that some barefooted person went out and hacked it off a tree. It’s hype. I don’t think it means anything.” Finally, participants were queried about the quality of supplements. They were asked how consumers could know if a supplement was pure and did not contain harmful ingredients. Twenty nine percent of participants said the only thing they could do was to trust the manufacturer and the information placed on the label. Some participants (23%) thought the only way to know if a supplement was pure was to read the ingredient list and look for fewer additives. One participant stated, “I would consider something more pure the less additives that are in it.” Ten percent of participants looked for the word “standardized” on supplement labels. “Mainly I look for the claim that it’s standardized. There’s no guarantee that somebody that says it’s standardized is telling the truth, but that would be one thing I look for.” Fifteen percent of participants stated that a consumer could not know if a product does not contain harmful ingredients. One person responded, “We don’t know; there is no way to know because they’re not regulated.” Finally, 10% of participants said they had to research the product themselves to determine if it was safe or effective.

4. Discussion Participants in this study appeared to represent many female supplement users reported in the literature. That is, supplement use is reported to be more prevalent among women, the better educated, and Caucasians, which is similar to the demographic characteristics of this sample [1,2,9,11,12,20]. The women in this study primarily obtained information about supplements from print material, family members, and friends. Other studies also found that supplement users obtained information from these sources [9,14,16]. Advice regarding supplement use was not frequently obtained from physicians or other health care providers in either this study or previous studies [4,9,14–16]. Participants in this study reported taking supplements primarily to prevent an illness or for energy enhancement, which also has been reported previously [4,14,21]. Finally, the most frequently consumed supplements among participants in this study (e.g. Vitamin C, Vitamin E, and a multivitamin) agreed with previous findings among supplement users [1,2,11]. Study participants’ knowledge of dietary sources and functions of vitamins and minerals was adequate. Most par-

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ticipants answered 7 of the 10 questions on the knowledge test correctly. One of the questions on the knowledge test asked participants to identify the nutrient that is recommended for women who are trying to become pregnant. The majority of the sample (70.6%) selected the correct answer, folic acid. In contrast, only 21% of the women surveyed in previous research knew folic acid is “something needed for pregnancy to help you to have a healthy baby” [22]. It should be noted that participants completed the test prior to the interview; thus, it was possible for them to consult resources to answer the questions. However, we do not have evidence to support or refute this practice. Knowledge of some information on supplement labels was adequate among study participants. Many participants could correctly identify dosing instructions and instructions regarding intended use of a supplement from information on the label. Knowledge of the purpose of the daily value on supplement labels also was fairly high. Participants knew the daily value indicated how much one serving of a supplement contributed to the recommended amount needed by the body. However, participants did not realize that daily values are established for vitamins and minerals but are not established for herbal preparations. Thus, several participants expressed skepticism about the validity of the words “not established” for the percent daily value on herbal products. Some participants in this study believed “natural” products were more wholesome and safe. However, the term “natural” is not defined for use on supplement labels [23]. Products labeled “natural” are not required by law to contain only natural ingredients. Thus, use of the term “natural” is misleading for many. Consumers need to be better informed about the ambiguity of the term on dietary supplement labels. Participants’ interpretation of the structure/function claim and disclaimer used on the echinacea label also was limited. Multiple interpretations of the meaning of the disclaimer were offered by participants. Thus, consumers need more education about the types of structure/function claims that can be used on labels and why the disclaimer is included on supplement labels. FDA does not authorize or test dietary supplements for safety or efficacy in relation to manufacturers’ claims on supplement labels [17]. Therefore, the disclaimer must accompany structure/function claims. Few participants in this study understood FDA’s role. Furthermore, participants demonstrated confusion about the government’s role in regulating the safety of dietary supplements. FDA review and approval of supplement ingredients are not required before marketing the product. Good manufacturing practices are expected to be followed by manufacturers to ensure safety [7]. Sound manufacturing practices specific to supplements do not yet exist. Thus, DSHEA authorized the FDA to establish those guidelines and FDA must prove that a supplement or ingredient is unsafe before it can restrict use of the supplement [7]. Some participants in this study knew that supplements are not well regulated but could not discuss the limitations of the regulatory process. Other participants did not acknowledge the limitations

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of the regulatory process; they believed consumers could trust all information on labels. Regular users of supplements in previous research believed that there is adequate testing of dietary supplements, and many respondents did not want to be denied access to supplements that had not been previously tested for safety [20]. Thus, consumers’ knowledge of product testing for safety is limited and deserves further investigation. Despite the knowledge gained from this research, several limitations exist. First, the sample primarily was composed of well educated, upper income women. While many women in this group consume supplements, others also consume supplements. Therefore, the findings from this research cannot be applied to all supplement users. For example, comprehension of supplement label information and product testing from lower income or male supplement users cannot be determined from this research. Furthermore, 20–50% of the adult population has poor or marginal literacy skills [24] and may understand little of the information on supplement labels. The educational needs of these individuals require further investigation. In conclusion, many female supplement users are knowledgeable about terms that are well defined on supplement labels. However, knowledge about product testing for safety and efficacy of dietary supplements may be limited. Little evidence exists to suggest that women of childbearing age will discontinue taking dietary supplements. Thus, educators need to identify clients who consume dietary supplements regularly and assess their knowledge of terms used on supplement labels and the regulatory statutes pertaining to supplements. Remind clients that manufacturers are responsible for the safety of dietary supplements and pre-market safety testing is not performed by FDA. Clarify the meaning of structure/function claims when misconceptions exist and reinforce the lack of daily values for herbal preparations. Consumers can make informed health care choices, as suggested in DSHEA, only when fully informed about the safety, efficacy and quality of products consumed for health promotion and disease prevention.

Acknowledgements The time and participation of study participants are deeply appreciated. Funding for this study was provided by USDA agreement #99-35207-8519.

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