Dairy foods are postulated to have beneficial effects on blood pressure, body fat, serum lipids, and the incidence of type 2 diabetes. To evaluate the effects of the consumption of milk and dairy products, we performed a randomized dietary intervention trial for 24 wk in Japanese men, aged 20 to 60 y, with 2 or more components of the metabolic syndrome (Clinical trial registration: UMIN000006353). Subjects were randomized to a control group (n=98) that received dietary intervention focused on weight control supervised by registered dietitians, and a dairy-consumption group (n=102) that received both dietary intervention and regular home dairy delivery of 400 g/d for 24 wk. Co-primary endpoints included waist circumference, blood pressure, fasting blood sugar (PBS), and serum lipids. The dietary intervention decreased energy intake from 2,150 to 1,850 kcal/d in both groups (p<0.01). Mean rates of compliance with the dairy-consumption intervention were over 90%, resulting in increased calcium intake in the dairy-consumption group from 329 to 667 mg/d (p<0.01). Co-primary endpoints improved in both groups, but the degree of improvement was smaller in the dairy-consumption group (one-sided p=0.99). Subgroup analyses specified in the study protocol identified weight and leisure-time physical activity (LTPA) as significant effect modifiers. Differences in changes in systolic blood pressure compared with the control group were -8.0 mmHg (95% CI, -14.0 to -1.9, interaction; p<0.01) in the normal weight group and -5.8 mmHg (-11.4 to -0.2, interaction; p=0.02) in the moderate-to-high LTPA group, indicating lower systolic blood pressure in the dairy-consumption group among participants in these subgroups. In conclusion, although effects on the co-primary endpoints of dairy consumption were not shown, dairy consumption lowered systolic blood pressure in the subgroups with normal weight and moderate-to-high LTPA and lowered PBS in the subgroup with normal weight.