Whole-grain consumption and the metabolic syndrome: a favorable association in Tehranian adults

Background: Although dietary guidelines recommend increased intake of grain products to prevent chronic diseases, epidemiologic data regarding whole-grain intake association with metabolic syndrome are sparse. Objective: To evaluate the relationship between whole-grain intakes, metabolic syndrome and metabolic risk factors in Tehranian adults. Design: Population-based cross-sectional study. Setting: Tehran, the capital of Iran. Subjects: A representative sample of 827 subjects (357 men and 470 women) aged 18-74 y. Methods: Usual dietary intake was assessed using a food frequency questionnaire. The procedure developed by Jacobs et al was used to classify grain products into whole and refined grains. Weight and height were measured according to standard protocols and body mass index was calculated. Fasting blood samples were taken for biochemical measurements and blood pressure was assessed according to standard methods. Hypertriglyceridemia, hypercholestrolemia, high LDL, low HDL and metabolic syndrome were defined according to ATP III guidelines and hypertension based on JNC VI. Diabetes was defined as fasting plasma glucose level of 126 mg/dl or 2-h postchallenge blood glucose level of 200 mg/dl. Subjects were categorized based on quartile cut-points of whole- and refined-grain intake. Results: Mean (s.d.) consumptions of whole and refined grains were 9329 and 20157 g/day, respectively. Both men and women reported higher intakes of refined grain than of whole grains. Compared with subjects in the lower quartile category, those in the upper category of whole-grain intake had lower prevalence of metabolic risk factors. Conversely, those in the higher category of refined-grain intake had higher prevalence of metabolic risk factors, except for diabetes. After controlling for confounders, a significantly decreasing trend was observed for the risk of having hypertriglyceridemia (odds ratios among quartiles: 1.00, 0.89, 0.74, 0.61, respectively), hypertension (1.00, 0.99, 0.93, 0.84) and metabolic syndrome (1.00, 0.84, 0.76, 0.68). Higher consumption of refined grains was associated with higher odds of having hypercholestrolemia (1.00, 1.07, 1.19, 1.23), hypertriglyceridemia (1.00, 1.17, 1.49, 2.01), hypertension (1.00, 1.22, 1.48, 1.69) and metabolic syndrome (1.00, 1.68, 1.92, 2.25). Conclusion: Whole-grain intake is inversely and refined-grain intake is positively associated with the risk of having metabolic syndrome. Recommendations to increase whole-grain intake may reduce this risk.