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Dietary breads: Myth or reality?
diabetes research and clinical practice 81 (2008) 68–71
available at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/diabres
Dietary breads: Myth or reality? Banu Mesci *, Aytekin Oguz 1, Hatice Gul Sagun 2, Mehmet Uzunlulu 3, Elmas Biberci Keskin 4, Damla Coksert 5 Goztepe Training and Research Hospital, Diabetes Clinic, Turkey
article info
abstract
Article history:
Aims: To assess the differences in acute effects of whole wheat bread, wheat bran bread and
Received 27 December 2007
rye bread – perceived as dietary(Low caloric!) breads – on glucose and insulin levels in
Accepted 13 February 2008
patients with type 2 diabetes, as compared to white wheat bread.
Published on line 26 March 2008
Methods: One hundred twenty one type 2 diabetic patients were randomized into three groups as whole wheat, wheat bran and rye bread groups. Each group ate 100 g of bread with
Keywords:
water with in 10 min. Blood glucose measurements were made at every 30 min in 2 h. Insulin
Type 2 diabetes
was measured at fasting and at the second hour in the patients who do not use insulin. The
Whole wheat bread
same processes were repeated on the following day, with white wheat bread for each group.
Wheat bran bread
Results: No significant difference was found in either glycemic or insulinemic effects
Rye bread
between four types of breads when compared to each other. ( p = 0.093 for glycemic effect
White wheat bread
and p = 0.297 for insulinemic effect). Conclusion: Three different bread types consumed as an alternative to white bread in Turkey, increase blood glucose levels of diabetic patients similar to white bread. # 2008 Elsevier Ireland Ltd. All rights reserved.
1.
Introduction
Bread is one of the main elements in the diet of Turkish people. It is a common belief that some kinds of bread are more appropriate for a diabetic diet, as they have less hyperglycemic effect. Many of the patients visiting our clinic, report that they eat wheat bran bread, rye bread and whole wheat bread as a part of their diet, without considering the amount they consumed. The aim of this study was to explain the acute effects of whole wheat bread, wheat bran bread and rye bread – perceived as dietary breads – on blood glucose and insulin
levels in patients with type 2 diabetes, as compared to white wheat bread.
2.
Subjects, materials and methods
The study involved 149 type 2 diabetic patients followed at Goztepe Training and Research Hospital all reported that they used to consume 50–100 g of bread at breakfast. Severe cardiac, liver and renal failure, hypersensitivity reaction to test foods, chewing and swallowing disorders, malabsorption,
* Corresponding author at: G, Suadiye Kadikoy, Oncu sk. Seher apt. No: 5/10, 34722, Turkey. Tel.: +90 5322923159; fax: +90 2165655526. E-mail addresses: [email protected] (B. Mesci), [email protected] (A. Oguz), [email protected] (H.G. Sagun), [email protected] (M. Uzunlulu), [email protected] (E.B. Keskin), [email protected] (D. Coksert). 1
Tel.: +90 5057745929; fax: +90 2165655526. Tel.: +90 5052633312; fax: +90 2165655526. 3 Tel.: +90 5326852744; fax: +90 2165655526. 4 Tel.: +90 53270901989; fax: +90 2165655526. 5 Tel.: +90 5059231359; fax: +90 2165655526. 0168-8227/$ – see front matter # 2008 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.diabres.2008.02.010 2
69
diabetes research and clinical practice 81 (2008) 68–71
having fasting blood glucose levels more than 199 mg/dl and being on intensive insulin treatment were exclusion criteria. Study protocol was approved by our local ethical committee (Date of approval: 11 January 2007 and decision no: 34/C) and designed in accordance with the Helsinki Declaration of 1975 as revised in 1983. Patients giving their written approval for participation were randomized into three main groups, which were given whole wheat, wheat bran and rye bread, respectively. Patients, were invited to the diabetes clinic after at least 12-h fasting on different days. Fasting blood glucose was measured from the capillary blood and venous blood was collected for measurement of fasting plasma insulin only from the patients who do not use insulin. First group ate 100 g of whole wheat bread. Second group ate 100 g of wheat bran bread and third group 100 g of rye bread with 0.5 l of water within 10 min. Capillary blood glucose was measured in every half an hour until the second hour from the moment they started to eat. Venous blood was also collected for blood insulin level at the second hour from 60 patients (20 patients from each group) whose fasting insulin levels were measured. The same processes were repeated on the following day, with white wheat bread. White wheat bread used in the study was made of only white flour, which was separated from wheat’s germ, fine and coarse bran. Wheat bran bread was made of white flour with an addition of the fine bran of the wheat grain and did not include any coarse bran and wheat germ. Whole wheat bread was made of whole grain wheat flour. In the manufacturing process of the whole wheat bread whole wheat is used in the same quantities as in the nature, including coarse bran, fine bran and wheat germ. Preparation of the rye bread, made of rye flour containing both the coarse bran and wheat germ did not exclude any content of wheat or rye, including the coarse bran and the germ, so the quantity of bran was adjusted to natural levels. Nutritional values of the breads are shown in Table 1. Bread used in the study was prepared as roll bread packages containing different types of 50-g breads (whole wheat bread, wheat bran bread, rye bread and white wheat bread).
Blood glucose measurements were made from capillary blood using glucometer (Johnson & Johnson Company Life Scan One touch horizon). Insulin values were measured by Hitachi modular E170 hormon device, Roche insu¨lin kit.
3.
Statistical analysis
Glucose and insulin reponses were assessed by the differences in blood glucose and insulin levels between initial and second hour measurements. Student’s paired t-test was used to compare the effects of different kinds of breads on blood glucose and insulin levels, and one-way ANOVA test was used to compare glycemic and insulinemic effects of all bread types. All analyses were conducted through SPSS 13 software.
4.
Results
28 of 149 patients were excluded from the study (12 of them for their absence on the second day, 5 for not eating all of their bread and 11 for having fasting blood glucose levels above 199 on the second day). The study was completed with 121 patients (77 F, 44 M). The mean age of patients was 57.1 and the mean duration of diabetes was 6.4 years. Mean blood pressure levels were found 141.3 mm/Hg systolic, and 83.06 mm/Hg diastolic. Mean BMI was 31.25 kg/m2. Mean waist circumference were 103.3 cm for women and 102.2 cm for men. 90 patients were taking oral antidiabetic drugs, 17 were taking basal insulin alone or combined with oral hypoglycemic agents, and 14 were only on a diet. Demographical data for the participants of the study are shown in Table 2. For all groups, blood glucose variation during the 2-h period showed a similar curve. Blood glucose reached the highest level at the 90 min and then started to decrease (Fig. 1). The blood glucose differences between second hour and fasting samples were 75.05 mg/dl with whole wheat bread and 77.66 mg/dl with white wheat bread in the first group ( p = 0.414). 94.91 mg/dl with wheat bran bread and
Table 1 – Nutritional values of different types of breads Nutritional values (in 100 g)
Whole wheat bread
Wheat bran bread
Rye bread
8.15 40.5
9.16 40.4
8.82 40
Protein (g) Carbohydrate (g)
White wheat bread 9 49
Table 2 – Demographic data of the patient group participating in the study Groups participating in the study
Group 1 Group 2 Group 3 All groups a b
N
Age (years)
BMI (kg/m2)
Waist circumference (cm)
Treatment
M
F
Diet only
a
OHA
b
BI or BI + OAD
39 42 40
55.6 56.1 59.8
30.40 32.19 31.10
100.6 101.8 104
109.9 108.9 99.8
8 4 2
23 36 31
8 2 7
121
57.1
31.25
103.3
102.2
14
90
17
OHA: oral hypoglycemic agent. BI: basal insulin treatment.
70
diabetes research and clinical practice 81 (2008) 68–71
Fig. 1 – Glycemic effects of different types of bread used in our study.
78.3 mg/dl with white wheat bread in the second group ( p = 0.153). 103.9 mg/dl with rye bread and 82.72 md/dl with white wheat bread in the third group ( p = 0.124). The differences in serum insulin levels between second hour and fasting samples were 34.56 U with whole wheat bread and 27.35 U with white wheat bread in the first group ( p = 0.441). 29.65 U with wheat bran bread and 25.89 U with white wheat bread in the second group ( p = 0.496). 40.35 U with rye bread and 36.15 U with white wheat bread in the third group ( p = 0.569). No significant difference was found in either glycemic or insulinemic effects between four types of breads when compared to each other. ( p = 0.093 for glycemic effect and p = 0.297 for insulinemic effect) (Table 3).
5.
Discussion
This study demonstrated that, in contrast to widely accepted by public, the effect of white bread on the increase of blood glucose level of patients with type 2 diabetes mellitus was not different than other types of bread. Many studies have shown that diets with lower glycemic indices and higher fiber content decrease the risk of developing type 2 diabetes and heart diseases, contribute to a higher life quality for diabetics and have some preventive and
curative effect against insulin resistance and metabolic syndrome [1–3]. Cereal grains are recommended for diabetic patients for their diets [4]. The cereal grain consists of endosperm, embryo and bran. Grinding process separates the bran and the embryo from the endosperm. The endosperm is rich in starch content. Other nutrients are concentrated on the outer layer of the grain. Consequently, nutritional content of the refined grain decreases and contains more starch. The major difference between whole grain food and refined grains is that in whole grain food, the bran and the germ are protected [5]. Viscous fibers, such as b glucan in oat bread delays gastric emptying and causes glucose to be released into the circulation more slowly [6,7]. Be cause of slower digestion of cereals with high grain content, they may elevate postprandial blood glucose less in diabetics [8]. Particle size of whole grain cereals is one of the factors that define their physiological effects. Unprocessed bran delays gastric emptying and accelerates transit through intestines [9]. In our study, blood glucose change showed a similar curve for all groups, peaking at the 90 min. Therefore, no absorption difference as affected by contents was considered between the compared bread types. There are other studies suggesting that different types of bread do not differ in terms of glycemic effect in single meal tests. Liljeberg et al. reported that in single meal tests, glycemic and insulinemic responses to cereal products based on whole—meal oats or barley were indistinguishable from those with white bread [10]. Glycemic index value may be found to vary between individuals, and between measurements repeated for different individuals. We observed interindividual variability of glycemic responses for white bread. Vega-Lopez et al. reported that interindividual variability is higher than intraindividual reproducibility of glycemic index values for commercial white bread [11]. The power of our study is that, the number of patient groups was greater than that of similar studies, and every patient in each group ate also white wheat bread. Since patients ate white wheat bread on the day following the very first day, possibility of any change in lifestyles or metabolic variation is relatively low. The weakness of our study, on the other hand, is that consumed bread types do not suggest any effects other than short-term glycemic and insulinemic effects. The absence of any significant difference in postprandial insulin levels between four type of breads in our study does not exclude the possible long-term effects of different breads. This study
Table 3 – Comparison of glycemic and insulinemic effects of all bread categories with white wheat bread Groups
Bread type
a
Blood glucose difference (mg/dl)
b
Blood insulin difference (U)
Group 1 n = 39
Whole wheat bread White wheat bread 1
75.05 77.66
p = 0.414
34.56 27.35
p = 0.441
Group 2 n = 42
Wheat bran bread White wheat bread 2
94.91 78.3
p = 0.153
29.65 25.89
p = 0.496
Group 3 n = 40
Rye bread White wheat bread 3
103.9 82.72
p = 0.124
40.35 36.15
p = 0.569
a b
Difference between the second hour blood glucose and fasting blood glucose. Difference between the second hour insulin level and fasting insulin level.
diabetes research and clinical practice 81 (2008) 68–71
alone is not enough to comment on effects of different types of bread on improving of diabetes control. Although favorable effects of the components contained in unrefined bread, such as grains, bran, fiber, magnesium, etc. is shown in a number of studies [12,13], it should be noted that quantity of bread in the diet of diabetics has to be limited. It may be a better option to receive needed fiber and vitamins from cereal grains, vegetables and legumes instead of bread. Most of the patients in our country believe that consuming non-white wheat bread is essential for a diabetic diet. This may lead patients to eat excessive amounts of other breads, bringing their blood glucose and weight regulations to a deadlock. This study demonstrates that bread types consumed as an alternative to white wheat bread in our country for diabetes or obesity, do not have less effect on blood glucose elevation than white wheat bread and over-consumption of such kinds of bread in the diets of diabetics could be a factor that prevents good glycemic control.
[2] [3]
[4] [5]
[6]
[7]
[8]
Acknowledgments [9]
We thank Doygun Bread Inc. for their support in baking the breads used in our study. The study does not have any financial sponsor.
Conflict of interest
[10]
[11]
The authors state that they have no conflict of interest.
references
[12] [13]
[1] Y. Amano, K. Kawakubo, J.S. Lee, A.C. Tang, M. Sugiyama, K. Mori, Correlation between dietary glycemic index and
71
cardiovascular disease risk factors among Japanese women, Eur. J. Clin. Nutr. 58 (2004) 1472–1478. A.R. Leeds, Glycemic index and heart disease, Am. J. Clin. Nutr. 76 (Suppl.) (2002) 286–289. S. Liu, J.E. Manson, M.J. Stampfer, F.B. Hu, E. Giovanucci, G.A. Colditz, et al., A prospective study of whole grain intake and risk of diabetes mellitus in US women, Am. J. Public Health 90 (2000) 1409–1415. American Diabetes Association. Standards of Medical Care in Diabetes-2006. Diabetes Care, 29(2006). 4–42S. J.L. Slavin, M.C. Martini, D.R. Jacobs, L. Marquart, Plausible mechanisms for the protectiveness of whole grains, Am. J. Clin. Nutr. 70 (Suppl.) (1999) 59–63. D.J. Jenkins, M. Axelsen, C.W. Kendall, L.S. Augustin, V. Vuksan, U. Smith, Dietary fibre, lente carbohydrates and the insulin-resistant disease, Br. J. Nutr. 83 (Suppl.) (2000) 157–163. J. Hallfrisch, Facn, K.M. Behall, Mechanisms of the effects of grains on insulin and glucose responses, J. Am. Coll. Nutr. 19 (Suppl. 3) (2000) 320–325. D.J. Jenkins, V. Wesson, T.M. Wolever, A.L. Jenkins, J. Kalmusky, S. Guidici, et al., Whole meal versus wholegrain breads:proportion of whole cracked grain and the glycaemic response, BMJ 297 (6654) (1988) 958–960. K. Wrick, J.B. Robertson, P.J. Van Soest, B.A. Lewis, J.M. Rivers, D.A. Roe, et al., The influence of dietary fiber source on human intestinal transit and stool output, J. Nutr. 113 (1983) 1464–1479. H.G.M. Liljeberg, Y.E. Granfelt, I.M.E. Bjorck, Products based on a high fiber barley genotype, but not a common barley or oats, lower postprandial glucose and insulin responses in healthy humans, J. Nutr. 126 (1996) 458–466. S. Vega-Lopez, L.M. Ausman, J.L. Griffith, A.H. Lichtenstein, I˙nterindividual variability and intraindividual reproducibility of glycemic index values for commercial white bread, Diab. Care 30 (6) (2007) 1412–1417. A.S. Truswell, Glyceamic index of foods, Eur. J. Clin. Nutr. 46 (Suppl. 2) (1992) 91–101. M.A. Pereira, D.R. Jacobs Jr., J.J. Pins, S.K. Raatz, M.D. Gross, J.L. Slavin, et al., Effect of whole grains on insulin sensitivity in overweight hyperinsulinemic adults, Am. J. Clin. Nutr. 75 (5) (2002) 848–855.
available at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/diabres
Dietary breads: Myth or reality? Banu Mesci *, Aytekin Oguz 1, Hatice Gul Sagun 2, Mehmet Uzunlulu 3, Elmas Biberci Keskin 4, Damla Coksert 5 Goztepe Training and Research Hospital, Diabetes Clinic, Turkey
article info
abstract
Article history:
Aims: To assess the differences in acute effects of whole wheat bread, wheat bran bread and
Received 27 December 2007
rye bread – perceived as dietary(Low caloric!) breads – on glucose and insulin levels in
Accepted 13 February 2008
patients with type 2 diabetes, as compared to white wheat bread.
Published on line 26 March 2008
Methods: One hundred twenty one type 2 diabetic patients were randomized into three groups as whole wheat, wheat bran and rye bread groups. Each group ate 100 g of bread with
Keywords:
water with in 10 min. Blood glucose measurements were made at every 30 min in 2 h. Insulin
Type 2 diabetes
was measured at fasting and at the second hour in the patients who do not use insulin. The
Whole wheat bread
same processes were repeated on the following day, with white wheat bread for each group.
Wheat bran bread
Results: No significant difference was found in either glycemic or insulinemic effects
Rye bread
between four types of breads when compared to each other. ( p = 0.093 for glycemic effect
White wheat bread
and p = 0.297 for insulinemic effect). Conclusion: Three different bread types consumed as an alternative to white bread in Turkey, increase blood glucose levels of diabetic patients similar to white bread. # 2008 Elsevier Ireland Ltd. All rights reserved.
1.
Introduction
Bread is one of the main elements in the diet of Turkish people. It is a common belief that some kinds of bread are more appropriate for a diabetic diet, as they have less hyperglycemic effect. Many of the patients visiting our clinic, report that they eat wheat bran bread, rye bread and whole wheat bread as a part of their diet, without considering the amount they consumed. The aim of this study was to explain the acute effects of whole wheat bread, wheat bran bread and rye bread – perceived as dietary breads – on blood glucose and insulin
levels in patients with type 2 diabetes, as compared to white wheat bread.
2.
Subjects, materials and methods
The study involved 149 type 2 diabetic patients followed at Goztepe Training and Research Hospital all reported that they used to consume 50–100 g of bread at breakfast. Severe cardiac, liver and renal failure, hypersensitivity reaction to test foods, chewing and swallowing disorders, malabsorption,
* Corresponding author at: G, Suadiye Kadikoy, Oncu sk. Seher apt. No: 5/10, 34722, Turkey. Tel.: +90 5322923159; fax: +90 2165655526. E-mail addresses: [email protected] (B. Mesci), [email protected] (A. Oguz), [email protected] (H.G. Sagun), [email protected] (M. Uzunlulu), [email protected] (E.B. Keskin), [email protected] (D. Coksert). 1
Tel.: +90 5057745929; fax: +90 2165655526. Tel.: +90 5052633312; fax: +90 2165655526. 3 Tel.: +90 5326852744; fax: +90 2165655526. 4 Tel.: +90 53270901989; fax: +90 2165655526. 5 Tel.: +90 5059231359; fax: +90 2165655526. 0168-8227/$ – see front matter # 2008 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.diabres.2008.02.010 2
69
diabetes research and clinical practice 81 (2008) 68–71
having fasting blood glucose levels more than 199 mg/dl and being on intensive insulin treatment were exclusion criteria. Study protocol was approved by our local ethical committee (Date of approval: 11 January 2007 and decision no: 34/C) and designed in accordance with the Helsinki Declaration of 1975 as revised in 1983. Patients giving their written approval for participation were randomized into three main groups, which were given whole wheat, wheat bran and rye bread, respectively. Patients, were invited to the diabetes clinic after at least 12-h fasting on different days. Fasting blood glucose was measured from the capillary blood and venous blood was collected for measurement of fasting plasma insulin only from the patients who do not use insulin. First group ate 100 g of whole wheat bread. Second group ate 100 g of wheat bran bread and third group 100 g of rye bread with 0.5 l of water within 10 min. Capillary blood glucose was measured in every half an hour until the second hour from the moment they started to eat. Venous blood was also collected for blood insulin level at the second hour from 60 patients (20 patients from each group) whose fasting insulin levels were measured. The same processes were repeated on the following day, with white wheat bread. White wheat bread used in the study was made of only white flour, which was separated from wheat’s germ, fine and coarse bran. Wheat bran bread was made of white flour with an addition of the fine bran of the wheat grain and did not include any coarse bran and wheat germ. Whole wheat bread was made of whole grain wheat flour. In the manufacturing process of the whole wheat bread whole wheat is used in the same quantities as in the nature, including coarse bran, fine bran and wheat germ. Preparation of the rye bread, made of rye flour containing both the coarse bran and wheat germ did not exclude any content of wheat or rye, including the coarse bran and the germ, so the quantity of bran was adjusted to natural levels. Nutritional values of the breads are shown in Table 1. Bread used in the study was prepared as roll bread packages containing different types of 50-g breads (whole wheat bread, wheat bran bread, rye bread and white wheat bread).
Blood glucose measurements were made from capillary blood using glucometer (Johnson & Johnson Company Life Scan One touch horizon). Insulin values were measured by Hitachi modular E170 hormon device, Roche insu¨lin kit.
3.
Statistical analysis
Glucose and insulin reponses were assessed by the differences in blood glucose and insulin levels between initial and second hour measurements. Student’s paired t-test was used to compare the effects of different kinds of breads on blood glucose and insulin levels, and one-way ANOVA test was used to compare glycemic and insulinemic effects of all bread types. All analyses were conducted through SPSS 13 software.
4.
Results
28 of 149 patients were excluded from the study (12 of them for their absence on the second day, 5 for not eating all of their bread and 11 for having fasting blood glucose levels above 199 on the second day). The study was completed with 121 patients (77 F, 44 M). The mean age of patients was 57.1 and the mean duration of diabetes was 6.4 years. Mean blood pressure levels were found 141.3 mm/Hg systolic, and 83.06 mm/Hg diastolic. Mean BMI was 31.25 kg/m2. Mean waist circumference were 103.3 cm for women and 102.2 cm for men. 90 patients were taking oral antidiabetic drugs, 17 were taking basal insulin alone or combined with oral hypoglycemic agents, and 14 were only on a diet. Demographical data for the participants of the study are shown in Table 2. For all groups, blood glucose variation during the 2-h period showed a similar curve. Blood glucose reached the highest level at the 90 min and then started to decrease (Fig. 1). The blood glucose differences between second hour and fasting samples were 75.05 mg/dl with whole wheat bread and 77.66 mg/dl with white wheat bread in the first group ( p = 0.414). 94.91 mg/dl with wheat bran bread and
Table 1 – Nutritional values of different types of breads Nutritional values (in 100 g)
Whole wheat bread
Wheat bran bread
Rye bread
8.15 40.5
9.16 40.4
8.82 40
Protein (g) Carbohydrate (g)
White wheat bread 9 49
Table 2 – Demographic data of the patient group participating in the study Groups participating in the study
Group 1 Group 2 Group 3 All groups a b
N
Age (years)
BMI (kg/m2)
Waist circumference (cm)
Treatment
M
F
Diet only
a
OHA
b
BI or BI + OAD
39 42 40
55.6 56.1 59.8
30.40 32.19 31.10
100.6 101.8 104
109.9 108.9 99.8
8 4 2
23 36 31
8 2 7
121
57.1
31.25
103.3
102.2
14
90
17
OHA: oral hypoglycemic agent. BI: basal insulin treatment.
70
diabetes research and clinical practice 81 (2008) 68–71
Fig. 1 – Glycemic effects of different types of bread used in our study.
78.3 mg/dl with white wheat bread in the second group ( p = 0.153). 103.9 mg/dl with rye bread and 82.72 md/dl with white wheat bread in the third group ( p = 0.124). The differences in serum insulin levels between second hour and fasting samples were 34.56 U with whole wheat bread and 27.35 U with white wheat bread in the first group ( p = 0.441). 29.65 U with wheat bran bread and 25.89 U with white wheat bread in the second group ( p = 0.496). 40.35 U with rye bread and 36.15 U with white wheat bread in the third group ( p = 0.569). No significant difference was found in either glycemic or insulinemic effects between four types of breads when compared to each other. ( p = 0.093 for glycemic effect and p = 0.297 for insulinemic effect) (Table 3).
5.
Discussion
This study demonstrated that, in contrast to widely accepted by public, the effect of white bread on the increase of blood glucose level of patients with type 2 diabetes mellitus was not different than other types of bread. Many studies have shown that diets with lower glycemic indices and higher fiber content decrease the risk of developing type 2 diabetes and heart diseases, contribute to a higher life quality for diabetics and have some preventive and
curative effect against insulin resistance and metabolic syndrome [1–3]. Cereal grains are recommended for diabetic patients for their diets [4]. The cereal grain consists of endosperm, embryo and bran. Grinding process separates the bran and the embryo from the endosperm. The endosperm is rich in starch content. Other nutrients are concentrated on the outer layer of the grain. Consequently, nutritional content of the refined grain decreases and contains more starch. The major difference between whole grain food and refined grains is that in whole grain food, the bran and the germ are protected [5]. Viscous fibers, such as b glucan in oat bread delays gastric emptying and causes glucose to be released into the circulation more slowly [6,7]. Be cause of slower digestion of cereals with high grain content, they may elevate postprandial blood glucose less in diabetics [8]. Particle size of whole grain cereals is one of the factors that define their physiological effects. Unprocessed bran delays gastric emptying and accelerates transit through intestines [9]. In our study, blood glucose change showed a similar curve for all groups, peaking at the 90 min. Therefore, no absorption difference as affected by contents was considered between the compared bread types. There are other studies suggesting that different types of bread do not differ in terms of glycemic effect in single meal tests. Liljeberg et al. reported that in single meal tests, glycemic and insulinemic responses to cereal products based on whole—meal oats or barley were indistinguishable from those with white bread [10]. Glycemic index value may be found to vary between individuals, and between measurements repeated for different individuals. We observed interindividual variability of glycemic responses for white bread. Vega-Lopez et al. reported that interindividual variability is higher than intraindividual reproducibility of glycemic index values for commercial white bread [11]. The power of our study is that, the number of patient groups was greater than that of similar studies, and every patient in each group ate also white wheat bread. Since patients ate white wheat bread on the day following the very first day, possibility of any change in lifestyles or metabolic variation is relatively low. The weakness of our study, on the other hand, is that consumed bread types do not suggest any effects other than short-term glycemic and insulinemic effects. The absence of any significant difference in postprandial insulin levels between four type of breads in our study does not exclude the possible long-term effects of different breads. This study
Table 3 – Comparison of glycemic and insulinemic effects of all bread categories with white wheat bread Groups
Bread type
a
Blood glucose difference (mg/dl)
b
Blood insulin difference (U)
Group 1 n = 39
Whole wheat bread White wheat bread 1
75.05 77.66
p = 0.414
34.56 27.35
p = 0.441
Group 2 n = 42
Wheat bran bread White wheat bread 2
94.91 78.3
p = 0.153
29.65 25.89
p = 0.496
Group 3 n = 40
Rye bread White wheat bread 3
103.9 82.72
p = 0.124
40.35 36.15
p = 0.569
a b
Difference between the second hour blood glucose and fasting blood glucose. Difference between the second hour insulin level and fasting insulin level.
diabetes research and clinical practice 81 (2008) 68–71
alone is not enough to comment on effects of different types of bread on improving of diabetes control. Although favorable effects of the components contained in unrefined bread, such as grains, bran, fiber, magnesium, etc. is shown in a number of studies [12,13], it should be noted that quantity of bread in the diet of diabetics has to be limited. It may be a better option to receive needed fiber and vitamins from cereal grains, vegetables and legumes instead of bread. Most of the patients in our country believe that consuming non-white wheat bread is essential for a diabetic diet. This may lead patients to eat excessive amounts of other breads, bringing their blood glucose and weight regulations to a deadlock. This study demonstrates that bread types consumed as an alternative to white wheat bread in our country for diabetes or obesity, do not have less effect on blood glucose elevation than white wheat bread and over-consumption of such kinds of bread in the diets of diabetics could be a factor that prevents good glycemic control.
[2] [3]
[4] [5]
[6]
[7]
[8]
Acknowledgments [9]
We thank Doygun Bread Inc. for their support in baking the breads used in our study. The study does not have any financial sponsor.
Conflict of interest
[10]
[11]
The authors state that they have no conflict of interest.
references
[12] [13]
[1] Y. Amano, K. Kawakubo, J.S. Lee, A.C. Tang, M. Sugiyama, K. Mori, Correlation between dietary glycemic index and
71
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