ARS | Publication request: Intake of whole grains, refined grains, and cereal fiber measured with 7-d diet records and associations with risk factors for chronic disease

Submitted to: American Journal of Clinical Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 1, 2007
Publication Date: December 1, 2007
Citation: Newby, P.K., Maras, J., Bakun, P., Muller, D., Ferrucci, L., Tucker, K. 2007. Intake of whole grains, refined grains, and cereal fiber measured with 7-d diet records and associations with risk factors for chronic disease. American Journal of Clinical Nutrition. 86:1745-1753.

Interpretive Summary: Fiber consumption has been shown to be related to decreased risk of several diseases, including colon cancer, heart disease, diabetes, diverticulosis, obesity, stroke, and the metabolic syndrome. Refined grains are the counterpart to whole grains, but evidence is conflicting about associations with metabolic and anthropometric variables. The objective of this study was to examine associations of the intakes of whole grains, refined grains, and cereal fiber measured with 7-d dietary records and quantified in gram weights with selected risk factors for chronic disease among adults participating in the Baltimore Longitudinal Study on Aging (BLSA). An additional goal was to explore whether associations with risk factors were modified by sex or body mass index (BMI; in kg/m2). We found that whole grains were significantly inversely associated with anthropometric variables (weight, BMI, and waist circumference), plasma lipid measures (total cholesterol and LDL cholesterol), and 2-h glucose. Cereal fiber was also related to these variables, and the magnitude of effects was similar. Refined grains were associated with fasting insulin among women but not men. In conclusion, our study shows significant and similar associations of whole grains and cereal fiber with weight, BMI, waist circumference, and total cholesterol. Refined grains were positively associated with fasting insulin among women but not men. Longitudinal studies are needed to reproduce these findings, and special attention should be dedicated to exploring potential interactions with BMI, sex, age, and genes.

Technical Abstract: Research studies examining foods are important, because they account for biological interactions that might otherwise be lost in the analysis of individual nutrients. Single-nutrient studies are also needed to explore the mechanisms by which foods may be protective. Our objective was to examine associations between whole grains, refined grains, and cereal fiber and chronic disease risk factors. In a cross-sectional analysis of participants in the Baltimore Longitudinal Study of Aging, associations between dietary intakes and risk factors were examined with multivariate linear regression analysis. Dietary intakes were assessed with 7-d dietary records and quantified in g/d. Compared with subjects in the lowest quintile (Q1) of whole-grain intake, subjects in the highest quintile (Q5) had lower body mass index (BMI; in kg/m2; Q1: 25.7; Q5: 24.2; P for trend = 0.0001) and weight (Q1: 75.4 kg; Q5: 72.2 kg; P for trend = 0.004) and smaller waist circumference (Q1: 87.8 cm; Q5: 84.4 cm; P for trend = 0.002). Whole grains were also inversely associated with total cholesterol (P for trend = 0.02), LDL cholesterol (P for trend = 0.04), and 2-h glucose (P for trend = 0.0006). Associations between cereal fiber and anthropometrics and plasma lipids were similar. In subgroup analyses, refined grains were positively associated with fasting insulin among women (P for trend = 0.002). Similar associations of whole grains and cereal fiber with weight, BMI, waist circumference, plasma cholesterol, and 2-h glucose were observed, suggesting that cereal fiber and its constituents may in part mediate these relations. Refined grains were associated with fasting insulin among women but not men. Additional research should explore potential interaction effects with BMI, sex, age, and genes.