Dairy intake and the insulin resistance syndrome in the CARDIA Study.
Little is known about the potential role of dairy consumption in the etiology of cardiovascular disease. We studied associations between reported dairy intake and components of the insulin resistance syndrome in a prospective study of young black and white adults. Participants attended up to five clinic examinations over a 10-year period beginning in 1985/6 (age = 18 to 35 years). The baseline and year-7 exam included a comprehensive diet history interview. Dependent variables include body mass index (BMI), waist-hip ratio (WHR), systolic blood pressure (SBP), and concentrations of fasting serum insulin, plasma triacylglycerol (Trg), and plasma HDL-cholesterol. Final sample size was 2929 after attrition and exclusions for diabetes, medication use, and pregnancy. Year 10 means of these variables were compared across quintiles of total dairy food and beverage intake with adjustment for their baseline values and for age, physical activity, smoking, education, race, sex, and intake of energy, alcohol, saturated fat, dietary fiber, and vitamin supplements. Dairy intake was associated with all components of the insulin resistance syndrome in a protective manner as follows: BMI: quintile 5 (> 28.4 times/wk) - quintile 1 (< 9.5 times/wk) = -0.5 kg/m2, p for linear trend across quintiles = .003; WHR: -0.01, p =.02; SBP: -1.9 mmHg, p=.02; insulin: -0.6 μU/ml, p = .02; Trg: -4.3 mg/dl, p = .04; HDL:+0.9 mg/dl, p = .12. Studies are needed to determine the mechanisms through which dairy intake may modify risk factors for cardiovascular disease.