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Study Overview
Objective. To evaluate the association between intake of dietary fiber and type 2 diabetes.
Design. Case-cohort study (EPIC-InterAct Study), which is nested within the large prospective cohort study EPIC (European Prospective Investigation into Cancer & Nutrition) [1]. EPIC includes participants from 10 European countries and was designed to investigate the relationships between diet, nutritional status, lifestyle, and environmental factors and the incidence of cancer and other chronic disease [1].
Setting and participants. The EPIC-Interact study used data from 8 European countries (Denmark, France, Germany, Italy, the Netherlands, Spain, Sweden, and UK). The Interact sample includes 12,403 individuals who were identified as having developed type 2 diabetes, and a random subcohort of controls who were free of diabetes at baseline (n = 16,835, including 778 cases of incident diabetes) selected from 340,234 eligible EPIC participants. Of the 28,460 participants in the EPIC-InterAct study, excluded were those with prevalent diabetes, missing diabetes status information, post-censoring diabetes, extreme energy intake (top and bottom 1%), and missing values for education level, physical activity, smoking status, and BMI, leaving a final sample of 11,559 cases and 15,258 subcohort participants. No differences were observed in baseline characteristics between the included and excluded participants.
Analysis. Country-specific hazard ratios (HRs) were estimated using Prentice-weighted Cox proportional hazards models and were pooled using a random effects meta-analysis. Dietary intake over the previous 12 months before recruitment was assessed by country-specific or center-specific assessment methods (food-frequency questionnaire and dietary histories) that were developed and validated locally, and data were converted to nutrient intake.
Main outcome measure. Incident cases of diabetes.
Main results. During a median of 10.8 years of follow-up, total fiber intake was associated with a lower risk of diabetes after adjusting for lifestyle and dietary factors (hazard ratio for the highest quartile of fiber intake [> 26 g/day] vs the lowest [< 19 g/day], 0.82; 95% confidence interval, 0.69–0.97, P for trend = 0.02). When the researchers focused on specific types of fiber, they found that people who consumed the highest amounts of cereal and vegetable fiber were 19% and 16%, respectively, less likely to develop type 2 diabetes compared with those who consumed the lowest amounts (P < 0.001). Intake of fruit fiber was not associated with risk of diabetes. When the analyses were additionally adjusted for BMI, the inverse associations between intake of fiber and diabetes were attenuated and no longer statistically significant.
The researchers also conducted a meta-analysis that included 18 other cohorts in addition to the current EPIC-InterAct study. The summary relative risks per 10/g day increase in intake were 0.91 (95% CI, 0.87–0.96) for total fiber, 0.75 (95% CI, 0.65–0.86) for cereal fiber, 0.95 (95% CI, 0.87–1.03) for fruit fiber, and 0.93 (95% CI 0.82–1.05) for vegetable fiber.
Conclusion. Individuals with diets rich in fiber, in particular cereal fiber, may be at lower risk of type 2 diabetes.
Commentary
The current study by the European InterAct Consortium adds to the available evidence supporting the association of dietary fiber and risk of diabetes. Higher intake of dietary fiber, especially cereal fiber, has been consistently associated with a lower risk of diabetes [2,3].
This study showed that a high intake of total fiber (primarily cereal and vegetable fiber) was associated with an 18% lower risk of type 2 diabetes (adjusted for dietary and lifestyle factors). While there was no association after adjusting for BMI, their meta-analysis of 18 studies did support the an inverse association between total fiber and cereal fiber intake and risk of type 2 diabetes.
What is it about fiber that is protective? With regard to whole grains, a rich source of fiber, potential mechanisms have been identified [5], including the possible impact of improved postprandial glucose response. However, whole grains are rich in nutrients and phytochemicals, and new hypotheses for the health-protective mechanisms of whole grains beyond fiber are being proposed [6]. In addition, the beneficial effect of fiber seen in this and other studies may be partly mediated by a lower BMI. Dietary fiber may affect appetite and energy intake through a range of processes.
It should be noted that although the effect of whole-grain foods for the prevention of type 2 diabetes is strongly supported by numerous epidemiological studies, a 2008 systematic review by the Cochrane Collaboration [4], which included 1 low-quality RCT and 11 cohort studies, stated that the evidence is too weak to be able to draw a definite conclusion about the preventive effect of this dietary factor.
Strengths of the study included its prospective design and large sample size. Limitations of the study include that dietary intake was assessed only at baseline and measurement error through the use of a questionnaire may have occurred. Although food-frequency questionnaires are widely used, they are subjective estimates and subject to recall bias, and some researchers have questioned their value for use in epidemiologic studies [7]. In addition, the authors note that the inverse association for total fiber and cereal fiber intake in the meta-analysis could be due to residual confounding as fiber intake has been associated with healthier diet, lower BMI, and greater physical activity.
Applications for Clinical Practice
The prevalence of type 2 diabetes has increased rapidly during the past decades in the United States. Dietary guidelines recommend the consumption of whole grains to prevent chronic diseases. The results presented in the current study strengthen the evidence supporting cereal fiber as an important determinant of type 2 diabetes risk. Randomized controlled trials are needed and should elucidate this matter.
1. Riboli E, Hunt KJ, Slimani N, European Prospective Investigation into Cancer and Nutrition (EPIC): study populations and data collection. Public Health Nutr 2002;5(6B):1113–24.
2. Ye EQ, Chacko SA, Chou EL, et al. Greater whole-grain intake is associated with lower risk of type 2 diabetes, cardiovascular disease, and weight gain. J Nutr 2012;142:1304–13.
3. Huang T, Xu M, Lee A, et al. Consumption of whole grains and cereal fiber and total and cause-specific mortality: prospective analysis of 367,442 individuals. BMC Med 2015;13:59.
4. Priebe MG, van Binsbergen JJ, de Vos R, Vonk RJ. Whole grain foods for theprevention of type 2 diabetes mellitus. Cochrane Database Syst Rev 2008;(1):CD006061.
5. Slavin JL, Martini MC, Jacobs DR Jr, Marquart L. Plausible mechanisms for the protectiveness of whole grains. Am J Clin Nutr 1999;70(3 Suppl):459S–463S.
6. Fardet A. New hypotheses for the health-protective mechanisms of whole-grain cereals: what is beyond fibre? Nutr Res Rev 2010;23:65–134.
7. Shim J-S, Oh K, Kim HC. Dietary assessment methods in epidemiologic studies. Epidemiol Health 2014;36:e2014009.
Study Overview
Objective. To evaluate the association between intake of dietary fiber and type 2 diabetes.
Design. Case-cohort study (EPIC-InterAct Study), which is nested within the large prospective cohort study EPIC (European Prospective Investigation into Cancer & Nutrition) [1]. EPIC includes participants from 10 European countries and was designed to investigate the relationships between diet, nutritional status, lifestyle, and environmental factors and the incidence of cancer and other chronic disease [1].
Setting and participants. The EPIC-Interact study used data from 8 European countries (Denmark, France, Germany, Italy, the Netherlands, Spain, Sweden, and UK). The Interact sample includes 12,403 individuals who were identified as having developed type 2 diabetes, and a random subcohort of controls who were free of diabetes at baseline (n = 16,835, including 778 cases of incident diabetes) selected from 340,234 eligible EPIC participants. Of the 28,460 participants in the EPIC-InterAct study, excluded were those with prevalent diabetes, missing diabetes status information, post-censoring diabetes, extreme energy intake (top and bottom 1%), and missing values for education level, physical activity, smoking status, and BMI, leaving a final sample of 11,559 cases and 15,258 subcohort participants. No differences were observed in baseline characteristics between the included and excluded participants.
Analysis. Country-specific hazard ratios (HRs) were estimated using Prentice-weighted Cox proportional hazards models and were pooled using a random effects meta-analysis. Dietary intake over the previous 12 months before recruitment was assessed by country-specific or center-specific assessment methods (food-frequency questionnaire and dietary histories) that were developed and validated locally, and data were converted to nutrient intake.
Main outcome measure. Incident cases of diabetes.
Main results. During a median of 10.8 years of follow-up, total fiber intake was associated with a lower risk of diabetes after adjusting for lifestyle and dietary factors (hazard ratio for the highest quartile of fiber intake [> 26 g/day] vs the lowest [< 19 g/day], 0.82; 95% confidence interval, 0.69–0.97, P for trend = 0.02). When the researchers focused on specific types of fiber, they found that people who consumed the highest amounts of cereal and vegetable fiber were 19% and 16%, respectively, less likely to develop type 2 diabetes compared with those who consumed the lowest amounts (P < 0.001). Intake of fruit fiber was not associated with risk of diabetes. When the analyses were additionally adjusted for BMI, the inverse associations between intake of fiber and diabetes were attenuated and no longer statistically significant.
The researchers also conducted a meta-analysis that included 18 other cohorts in addition to the current EPIC-InterAct study. The summary relative risks per 10/g day increase in intake were 0.91 (95% CI, 0.87–0.96) for total fiber, 0.75 (95% CI, 0.65–0.86) for cereal fiber, 0.95 (95% CI, 0.87–1.03) for fruit fiber, and 0.93 (95% CI 0.82–1.05) for vegetable fiber.
Conclusion. Individuals with diets rich in fiber, in particular cereal fiber, may be at lower risk of type 2 diabetes.
Commentary
The current study by the European InterAct Consortium adds to the available evidence supporting the association of dietary fiber and risk of diabetes. Higher intake of dietary fiber, especially cereal fiber, has been consistently associated with a lower risk of diabetes [2,3].
This study showed that a high intake of total fiber (primarily cereal and vegetable fiber) was associated with an 18% lower risk of type 2 diabetes (adjusted for dietary and lifestyle factors). While there was no association after adjusting for BMI, their meta-analysis of 18 studies did support the an inverse association between total fiber and cereal fiber intake and risk of type 2 diabetes.
What is it about fiber that is protective? With regard to whole grains, a rich source of fiber, potential mechanisms have been identified [5], including the possible impact of improved postprandial glucose response. However, whole grains are rich in nutrients and phytochemicals, and new hypotheses for the health-protective mechanisms of whole grains beyond fiber are being proposed [6]. In addition, the beneficial effect of fiber seen in this and other studies may be partly mediated by a lower BMI. Dietary fiber may affect appetite and energy intake through a range of processes.
It should be noted that although the effect of whole-grain foods for the prevention of type 2 diabetes is strongly supported by numerous epidemiological studies, a 2008 systematic review by the Cochrane Collaboration [4], which included 1 low-quality RCT and 11 cohort studies, stated that the evidence is too weak to be able to draw a definite conclusion about the preventive effect of this dietary factor.
Strengths of the study included its prospective design and large sample size. Limitations of the study include that dietary intake was assessed only at baseline and measurement error through the use of a questionnaire may have occurred. Although food-frequency questionnaires are widely used, they are subjective estimates and subject to recall bias, and some researchers have questioned their value for use in epidemiologic studies [7]. In addition, the authors note that the inverse association for total fiber and cereal fiber intake in the meta-analysis could be due to residual confounding as fiber intake has been associated with healthier diet, lower BMI, and greater physical activity.
Applications for Clinical Practice
The prevalence of type 2 diabetes has increased rapidly during the past decades in the United States. Dietary guidelines recommend the consumption of whole grains to prevent chronic diseases. The results presented in the current study strengthen the evidence supporting cereal fiber as an important determinant of type 2 diabetes risk. Randomized controlled trials are needed and should elucidate this matter.
Study Overview
Objective. To evaluate the association between intake of dietary fiber and type 2 diabetes.
Design. Case-cohort study (EPIC-InterAct Study), which is nested within the large prospective cohort study EPIC (European Prospective Investigation into Cancer & Nutrition) [1]. EPIC includes participants from 10 European countries and was designed to investigate the relationships between diet, nutritional status, lifestyle, and environmental factors and the incidence of cancer and other chronic disease [1].
Setting and participants. The EPIC-Interact study used data from 8 European countries (Denmark, France, Germany, Italy, the Netherlands, Spain, Sweden, and UK). The Interact sample includes 12,403 individuals who were identified as having developed type 2 diabetes, and a random subcohort of controls who were free of diabetes at baseline (n = 16,835, including 778 cases of incident diabetes) selected from 340,234 eligible EPIC participants. Of the 28,460 participants in the EPIC-InterAct study, excluded were those with prevalent diabetes, missing diabetes status information, post-censoring diabetes, extreme energy intake (top and bottom 1%), and missing values for education level, physical activity, smoking status, and BMI, leaving a final sample of 11,559 cases and 15,258 subcohort participants. No differences were observed in baseline characteristics between the included and excluded participants.
Analysis. Country-specific hazard ratios (HRs) were estimated using Prentice-weighted Cox proportional hazards models and were pooled using a random effects meta-analysis. Dietary intake over the previous 12 months before recruitment was assessed by country-specific or center-specific assessment methods (food-frequency questionnaire and dietary histories) that were developed and validated locally, and data were converted to nutrient intake.
Main outcome measure. Incident cases of diabetes.
Main results. During a median of 10.8 years of follow-up, total fiber intake was associated with a lower risk of diabetes after adjusting for lifestyle and dietary factors (hazard ratio for the highest quartile of fiber intake [> 26 g/day] vs the lowest [< 19 g/day], 0.82; 95% confidence interval, 0.69–0.97, P for trend = 0.02). When the researchers focused on specific types of fiber, they found that people who consumed the highest amounts of cereal and vegetable fiber were 19% and 16%, respectively, less likely to develop type 2 diabetes compared with those who consumed the lowest amounts (P < 0.001). Intake of fruit fiber was not associated with risk of diabetes. When the analyses were additionally adjusted for BMI, the inverse associations between intake of fiber and diabetes were attenuated and no longer statistically significant.
The researchers also conducted a meta-analysis that included 18 other cohorts in addition to the current EPIC-InterAct study. The summary relative risks per 10/g day increase in intake were 0.91 (95% CI, 0.87–0.96) for total fiber, 0.75 (95% CI, 0.65–0.86) for cereal fiber, 0.95 (95% CI, 0.87–1.03) for fruit fiber, and 0.93 (95% CI 0.82–1.05) for vegetable fiber.
Conclusion. Individuals with diets rich in fiber, in particular cereal fiber, may be at lower risk of type 2 diabetes.
Commentary
The current study by the European InterAct Consortium adds to the available evidence supporting the association of dietary fiber and risk of diabetes. Higher intake of dietary fiber, especially cereal fiber, has been consistently associated with a lower risk of diabetes [2,3].
This study showed that a high intake of total fiber (primarily cereal and vegetable fiber) was associated with an 18% lower risk of type 2 diabetes (adjusted for dietary and lifestyle factors). While there was no association after adjusting for BMI, their meta-analysis of 18 studies did support the an inverse association between total fiber and cereal fiber intake and risk of type 2 diabetes.
What is it about fiber that is protective? With regard to whole grains, a rich source of fiber, potential mechanisms have been identified [5], including the possible impact of improved postprandial glucose response. However, whole grains are rich in nutrients and phytochemicals, and new hypotheses for the health-protective mechanisms of whole grains beyond fiber are being proposed [6]. In addition, the beneficial effect of fiber seen in this and other studies may be partly mediated by a lower BMI. Dietary fiber may affect appetite and energy intake through a range of processes.
It should be noted that although the effect of whole-grain foods for the prevention of type 2 diabetes is strongly supported by numerous epidemiological studies, a 2008 systematic review by the Cochrane Collaboration [4], which included 1 low-quality RCT and 11 cohort studies, stated that the evidence is too weak to be able to draw a definite conclusion about the preventive effect of this dietary factor.
Strengths of the study included its prospective design and large sample size. Limitations of the study include that dietary intake was assessed only at baseline and measurement error through the use of a questionnaire may have occurred. Although food-frequency questionnaires are widely used, they are subjective estimates and subject to recall bias, and some researchers have questioned their value for use in epidemiologic studies [7]. In addition, the authors note that the inverse association for total fiber and cereal fiber intake in the meta-analysis could be due to residual confounding as fiber intake has been associated with healthier diet, lower BMI, and greater physical activity.
Applications for Clinical Practice
The prevalence of type 2 diabetes has increased rapidly during the past decades in the United States. Dietary guidelines recommend the consumption of whole grains to prevent chronic diseases. The results presented in the current study strengthen the evidence supporting cereal fiber as an important determinant of type 2 diabetes risk. Randomized controlled trials are needed and should elucidate this matter.
1. Riboli E, Hunt KJ, Slimani N, European Prospective Investigation into Cancer and Nutrition (EPIC): study populations and data collection. Public Health Nutr 2002;5(6B):1113–24.
2. Ye EQ, Chacko SA, Chou EL, et al. Greater whole-grain intake is associated with lower risk of type 2 diabetes, cardiovascular disease, and weight gain. J Nutr 2012;142:1304–13.
3. Huang T, Xu M, Lee A, et al. Consumption of whole grains and cereal fiber and total and cause-specific mortality: prospective analysis of 367,442 individuals. BMC Med 2015;13:59.
4. Priebe MG, van Binsbergen JJ, de Vos R, Vonk RJ. Whole grain foods for theprevention of type 2 diabetes mellitus. Cochrane Database Syst Rev 2008;(1):CD006061.
5. Slavin JL, Martini MC, Jacobs DR Jr, Marquart L. Plausible mechanisms for the protectiveness of whole grains. Am J Clin Nutr 1999;70(3 Suppl):459S–463S.
6. Fardet A. New hypotheses for the health-protective mechanisms of whole-grain cereals: what is beyond fibre? Nutr Res Rev 2010;23:65–134.
7. Shim J-S, Oh K, Kim HC. Dietary assessment methods in epidemiologic studies. Epidemiol Health 2014;36:e2014009.
1. Riboli E, Hunt KJ, Slimani N, European Prospective Investigation into Cancer and Nutrition (EPIC): study populations and data collection. Public Health Nutr 2002;5(6B):1113–24.
2. Ye EQ, Chacko SA, Chou EL, et al. Greater whole-grain intake is associated with lower risk of type 2 diabetes, cardiovascular disease, and weight gain. J Nutr 2012;142:1304–13.
3. Huang T, Xu M, Lee A, et al. Consumption of whole grains and cereal fiber and total and cause-specific mortality: prospective analysis of 367,442 individuals. BMC Med 2015;13:59.
4. Priebe MG, van Binsbergen JJ, de Vos R, Vonk RJ. Whole grain foods for theprevention of type 2 diabetes mellitus. Cochrane Database Syst Rev 2008;(1):CD006061.
5. Slavin JL, Martini MC, Jacobs DR Jr, Marquart L. Plausible mechanisms for the protectiveness of whole grains. Am J Clin Nutr 1999;70(3 Suppl):459S–463S.
6. Fardet A. New hypotheses for the health-protective mechanisms of whole-grain cereals: what is beyond fibre? Nutr Res Rev 2010;23:65–134.
7. Shim J-S, Oh K, Kim HC. Dietary assessment methods in epidemiologic studies. Epidemiol Health 2014;36:e2014009.