Effects of dietary intake of soy protein and isoflavones on cardiovascular disease risk factors in high risk, middle-aged men in Scotland.

OBJECTIVE: To investigate the effects of soy protein and isoflavones on blood pressure (BP) and cholesterol levels among high risk middle-aged Scottish men.

DESIGN: A randomized, double-blind, placebo-controlled, parallel-group dietary intervention study

SETTING: Inhabitants on Isles of Lewis and Harris in Scotland

SUBJECTS: Sixty-one men with relatively higher BP and/or total cholesterol (TC) levels aged 45 to 59 went through the dietary intervention.

INTERVENTION: Diets containing at least 20 g of soy protein and 80 mg of isoflavones were compared to the placebo diets. Intervention period was 5 weeks duration.

RESULTS: Significant difference was found in 24-hour urinary isoflavone excretion between the two groups after intervention. Significant reductions from the baselines were observed in systolic BP (SBP) and diastolic BP (DBP), TC and non-high density lipoprotein cholesterol (non-HDL-C) in the soy-containing diet group, but not in the olive oil containing active placebo group. Significant increases in high density lipoprotein cholesterol (HDL-C) were observed in both groups.

CONCLUSION: Dietary intakes of soy protein (at least 20 g) and isoflavones (at least 80 mg) for 5 weeks would be effective in reducing CHD risk among high-risk, middle-aged men.