A prospective study of whole-grain intake and risk of type 2 diabetes mellitus in US women. Whole-grain foods, dietary fiber, and type 2 diabetes: searching for a kernel of truth. Whole-grain intake and the risk of type 2 diabetes: a prospective study in men. Whole-grain and fiber intake and the incidence of type 2 diabetes. Effect of whole grains on insulin sensitivity in overweight hyperinsulinemic adults. Dietary fiber, glycemic load, and risk of non-insulin-dependent diabetes mellitus in women. Dietary fiber, glycemic load, and risk of NIDDM in men. Carbohydrates, dietary fiber, and incident type 2 diabetes in older women. Dietary fiber intake and glycemic index and incidence of diabetes in African-American and white adults: the ARIC study. Changes in whole-grain, bran, and cereal fiber consumption in relation to 8-y weight gain among men. Glycemic index, glycemic load, and dietary fiber intake and incidence of type 2 diabetes in younger and middle-aged women.
This study examined the association between intake of whole vs refined grain and the risk of type 2 diabetes mellitus.
                We used a food frequency questionnaire for repeated dietary assessments to prospectively evaluate the relation between whole-grain intake and the risk of diabetes mellitus in a cohort of 75,521 women aged 38 to 63 years without a previous diagnosis of diabetes or cardiovascular disease in 1984.
                During the 10-year follow-up, we confirmed 1879 incident cases of diabetes mellitus. When the highest and the lowest quintiles of intake were compared, the age and energy-adjusted relative risks were 0.62 (95% confidence interval [CI] = 0.53, 0.71, P trend < .0001) for whole grain, 1.31 (95% CI = 1.12, 1.53, P trend = .0003) for refined grain, and 1.57 (95% CI = 1.36, 1.82, P trend < .0001) for the ratio of refined- to whole-grain intake. These findings remained significant in multivariate analyses. The findings were most evident for women with a body mass index greater than 25 and were not entirely explained by dietary fiber, magnesium, and vitamin E.
                These findings suggest that substituting whole- for refined-grain products may decrease the risk of diabetes mellitus. nan Certain dietary components may play a role in the prevention of type 2 diabetes.
                We examined prospectively the associations between whole- and refined-grain intake and the risk of type 2 diabetes in a large cohort of men.
                Men from the Health Professionals Follow-up Study without a history of diabetes or cardiovascular disease in 1986 (n = 42898) were followed for </=12 y. Intakes of whole and refined grains, measured every 4 y by use of food-frequency questionnaires, were used to predict subsequent type 2 diabetes risk through multivariate analysis.
                We ascertained 1197 cases of incident type 2 diabetes. After adjustment for age; physical activity; cigarette smoking; alcohol consumption; family history of diabetes; and fruit, vegetable, and energy intakes, the relative risk of type 2 diabetes was 0.58 (95% CI: 0.47, 0.70; P for trend < 0.0001) comparing the highest with the lowest quintile of whole-grain intake. The association was moderately attenuated when additionally adjusted for body mass index (relative risk: 0.70; 95% CI: 0.57, 0.85; P for trend = 0.0006). Intake of refined grains was not significantly associated with risk of type 2 diabetes. After further adjustment for magnesium intake, cereal fiber intake, and glycemic load, the association between whole grains and type 2 diabetes was attenuated and the trend no longer significant.
                In men, a diet high in whole grains is associated with a reduced risk of type 2 diabetes in men that may be mediated by cereal fiber. Efforts should be made to replace refined-grain with whole-grain foods. Epidemiologic evidence of a preventive effect of whole grain against type 2 diabetes is mainly based on data from women. Information specific to men and women is needed.
                The objective was to study the relation between the intake of whole grain and fiber and the subsequent incidence of type 2 diabetes.
                The design was a cohort study of 2286 men and 2030 women aged 40-69 y and initially free of diabetes. Food consumption data were collected from 1966 through 1972 with the use of a dietary history interview covering the habitual diet during the previous year. During a 10-y follow-up, incident type 2 diabetes cases were identified in 54 men and 102 women from a nationwide register.
                Whole-grain consumption was associated with a reduced risk of type 2 diabetes. The relative risk (adjusted for age, sex, geographic area, smoking status, body mass index, energy intake, and intakes of vegetables, fruit, and berries) between the highest and lowest quartiles of whole-grain consumption was 0.65 (95% CI: 0.36, 1.18; P for trend = 0.02). Cereal fiber intake was also associated with a reduced risk of type 2 diabetes. The relative risk between the extreme quartiles of cereal fiber intake was 0.39 (95% CI: 0.20, 0.77; P = 0.01).
                An inverse association between whole-grain intake and the risk of type 2 diabetes was found. The similar result for cereal fiber intake suggests that the whole-grain association is due to cereal fiber or another factor related to cereal fiber intake. Epidemiologic studies have found whole-grain intake to be inversely associated with the risk of type 2 diabetes and heart disease.
                We tested the hypothesis that whole-grain consumption improves insulin sensitivity in overweight and obese adults.
                This controlled experiment compared insulin sensitivity between diets (55% carbohydrate, 30% fat) including 6-10 servings/d of breakfast cereal, bread, rice, pasta, muffins, cookies, and snacks of either whole or refined grains. Total energy needs were estimated to maintain body weight. Eleven overweight or obese [body mass index (in kg/m(2)): 27-36] hyperinsulinemic adults aged 25-56 y participated in a randomized crossover design. At the end of each 6-wk diet period, the subjects consumed 355 mL (12 oz) of a liquid mixed meal, and blood samples were taken over 2 h. The next day a euglycemic hyperinsulinemic clamp test was administered.
                Fasting insulin was 10% lower during consumption of the whole-grain than during consumption of the refined-grain diet (mean difference: -15 +/- 5.5 pmol/L; P = 0.03). After the whole-grain diet, the area under the 2-h insulin curve tended to be lower (-8832 pmol.min/L; 95% CI: -18720, 1062) than after the refined-grain diet. The rate of glucose infusion during the final 30 min of the clamp test was higher after the whole-grain diet (0.07 x 10(-4) mmol.kg(-1).min(-1) per pmol/L; 95% CI: 0.003 x 10(-4), 0.144 x 10(-4)).
                Insulin sensitivity may be an important mechanism whereby whole-grain foods reduce the risk of type 2 diabetes and heart disease. To examine prospectively the relationship between glycemic diets, low fiber intake, and risk of non-insulin-dependent diabetes mellitus.
                Cohort study.
                In 1986, a total of 65173 US women 40 to 65 years of age and free from diagnosed cardiovascular disease, cancer, and diabetes completed a detailed dietary questionnaire from which we calculated usual intake of total and specific sources of dietary fiber, dietary glycemic index, and glycemic load.
                Non-insulin-dependent diabetes mellitus.
                During 6 years of follow-up, 915 incident cases of diabetes were documented. The dietary glycemic index was positively associated with risk of diabetes after adjustment for age, body mass index, smoking, physical activity, family history of diabetes, alcohol and cereal fiber intake, and total energy intake. Comparing the highest with the lowest quintile, the relative risk (RR) of diabetes was 1.37 (95% confidence interval [CI], 1.09-1.71, P trend=.005). The glycemic load (an indicator of a global dietary insulin demand) was also positively associated with diabetes (RR= 1.47; 95% CI, 1.16-1.86, P trend=.003). Cereal fiber intake was inversely associated with risk of diabetes when comparing the extreme quintiles (RR=0.72, 95% CI, 0.58-0.90, P trend=.001). The combination of a high glycemic load and a low cereal fiber intake further increased the risk of diabetes (RR=2.50, 95% CI, 1.14-5.51) when compared with a low glycemic load and high cereal fiber intake.
                Our results support the hypothesis that diets with a high glycemic load and a low cereal fiber content increase risk of diabetes in women. Further, they suggest that grains should be consumed in a minimally refined form to reduce the incidence of diabetes. Intake of carbohydrates that provide a large glycemic response has been hypothesized to increase the risk of NIDDM, whereas dietary fiber is suspected to reduce incidence. These hypotheses have not been evaluated prospectively.
                We examined the relationship between diet and risk of NIDDM in a cohort of 42,759 men without NIDDM or cardiovascular disease, who were 40-75 years of age in 1986. Diet was assessed at baseline by a validated semiquantitative food frequency questionnaire. During 6-years of follow-up, 523 incident cases of NIDDM were documented.
                The dietary glycemic index (an indicator of carbohydrate's ability to raise blood glucose levels) was positively associated with risk of NIDDM after adjustment for age, BMI, smoking, physical activity, family history of diabetes, alcohol consumption, cereal fiber, and total energy intake. Comparing the highest and lowest quintiles, the relative risk (RR) of NIDDM was 1.37 (95% CI, 1.02-1.83, P trend = 0.03). Cereal fiber was inversely associated with risk of NIDDM (RR = 0.70; 95% CI, 0.51-0.96, P trend = 0.007; for > 8.1 g/day vs. < 3.2 g/day). The combination of a high glycemic load and a low cereal fiber intake further increased the risk of NIDDM (RR = 2.17, 95% CI, 1.04-4.54) when compared with a low glycemic load and high cereal fiber intake.
                These findings support the hypothesis that diets with a high glycemic load and a low cereal fiber content increase risk of NIDDM in men. Further, they suggest that grains should be consumed in a minimally refined form to reduce the incidence of NIDDM. Dietary carbohydrates may influence the development of type 2 (non-insulin-dependent) diabetes, for example, through effects on blood glucose and insulin concentrations.
                We examined the relations of baseline intake of carbohydrates, dietary fiber, dietary magnesium, and carbohydrate-rich foods and the glycemic index with incidence of diabetes.
                This was a prospective cohort study of 35988 older Iowa women initially free of diabetes. During 6 y of follow-up, 1141 incident cases of diabetes were reported.
                Total grain, whole-grain, total dietary fiber, cereal fiber, and dietary magnesium intakes showed strong inverse associations with incidence of diabetes after adjustment for potential nondietary confounding variables. Multivariate-adjusted relative risks of diabetes were 1.0, 0.99, 0.98, 0.92, and 0.79 (P for trend: 0.0089) across quintiles of whole-grain intake; 1.0, 1.09, 1.00, 0.94, and 0.78 (P for trend: 0.005) across quintiles of total dietary fiber intake; and 1.0, 0.81, 0.82, 0.81, and 0.67 (P for trend: 0.0003) across quintiles of dietary magnesium intake. Intakes of total carbohydrates, refined grains, fruit and vegetables, and soluble fiber and the glycemic index were unrelated to diabetes risk.
                These data support a protective role for grains (particularly whole grains), cereal fiber, and dietary magnesium in the development of diabetes in older women. To determine the association of dietary fiber and glycemic index with incident type 2 diabetes in African-Americans and whites.
                We studied 12,251 adults aged 45-64 years and free of diabetes at baseline (1987-1989). A total of 1,447 cases of diabetes were reported between baseline and 9 years of follow-up. Diabetes status was determined by fasting glucose level > or =126 mg/dl (7.0 mmol/l), nonfasting glucose level > or =200 mg/dl (11.1 mmol/l), self-report of physician diagnosis, or use of diabetes medication. Usual dietary intake over the previous year was obtained at baseline using a 66-item food-frequency questionnaire. Nutrients were energy-adjusted using the residuals method. Proportional hazard regression analysis was used to examine dietary fiber intake and glycemic index as predictors of type 2 diabetes in both ethnic groups.
                After adjustment for age, BMI, education, smoking status, physical activity, sex, and field center, there were no statistically significant associations of intake of total dietary fiber, fruit fiber, legume fiber, glycemic index, or glycemic load with incident diabetes. The hazard ratio for the fifth compared with the first quintile of cereal fiber was 0.75 (95% CI 0.60-0.92) in whites and 0.86 (0.65-1.15) in African-Americans.
                This finding supports a protective role for cereal fiber in the development of diabetes in whites. More studies are needed to determine the role of dietary fiber and glycemic index in diabetes in African-Americans. Epidemiologic studies that directly examine changes in whole-grain consumption in relation to weight gain are sparse, and characterization of this association has been obscured by methodologic inconsistencies in the assessment of whole grains.
                We aimed to ascertain the associations between changes in new quantitative estimates of whole-grain intake and 8-y weight gain among US men.
                The study was conducted in a prospective cohort of 27 082 men aged 40-75 y at baseline in 1986. Data on lifestyle factors were obtained periodically by using self-reported questionnaires, and participants measured and reported their body weight in 1986 and 1994.
                In multivariate analyses, an increase in whole-grain intake was inversely associated with long-term weight gain (P for trend < 0.0001). A dose-response relation was observed, and for every 40-g/d increment in whole-grain intake from all foods, weight gain was reduced by 0.49 kg. Bran that was added to the diet or obtained from fortified-grain foods further reduced the risk of weight gain (P for trend = 0.01), and, for every 20 g/d increase in intake, weight gain was reduced by 0.36 kg. Changes in cereal and fruit fiber were inversely related to weight gain. No associations were observed between changes in refined-grain or added germ consumption and body weight.
                The increased consumption of whole grains was inversely related to weight gain, and the associations persisted after changes in added bran or fiber intakes were accounted for. This suggests that additional components in whole grains may contribute to favorable metabolic alterations that may reduce long-term weight gain. Increasing evidence suggests an important role of carbohydrate quality in the development of type 2 diabetes.
                Our objective was to prospectively examine the association between glycemic index, glycemic load, and dietary fiber and the risk of type 2 diabetes in a large cohort of young women.
                In 1991, 91249 women completed a semiquantitative food-frequency questionnaire that assessed dietary intake. The women were followed for 8 y for the development of incident type 2 diabetes, and dietary information was updated in 1995.
                We identified 741 incident cases of confirmed type 2 diabetes during 8 y (716 300 person-years) of follow-up. After adjustment for age, body mass index, family history of diabetes, and other potential confounders, glycemic index was significantly associated with an increased risk of diabetes (multivariate relative risks for quintiles 1-5, respectively: 1, 1.15, 1.07, 1.27, and 1.59; 95% CI: 1.21, 2.10; P for trend = 0.001). Conversely, cereal fiber intake was associated with a decreased risk of diabetes (multivariate relative risks for quintiles 1-5, respectively: 1, 0.85, 0.87, 0.82, and 0.64; 95% CI: 0.48, 0.86; P for trend = 0.004). Glycemic load was not significantly associated with risk in the overall cohort (multivariate relative risks for quintiles 1-5, respectively: 1, 1.31, 1.20, 1.14, and 1.33; 95% CI: 0.92, 1.91; P for trend = 0.21).
                A diet high in rapidly absorbed carbohydrates and low in cereal fiber is associated with an increased risk of type 2 diabetes.
The evidence from only prospective cohort trials is considered to be too weak to be able to draw a definite conclusion about the preventive effect of whole grain foods on the development of T2DM. Properly designed long-term randomised controlled trials are needed. To facilitate this, further mechanistic research should focus on finding a set of relevant intermediate endpoints for T2DM and on identifying genetic subgroups of the population at risk that are most susceptible to dietary intervention.