A total of 265 (87%) participants completed all study visits. Small differences between groups for serum apolipoprotein B100 change [repeated measures ANOVA, P = 0.04; mean (SD), −1.0 (10.0) mg/dl (400 IU); −1.0 (10.0) mg/dl (1000 IU); and +0.02 (10.0) mg/dl (placebo)] were not considered clinically significant. Other systemic markers for CVD risk remained unchanged. There was significant seasonal variation in systolic and diastolic blood pressure independent of vitamin D dose (P < 0.001, linear mixed model). Mean (SD) reduction in systolic blood pressure from winter to summer was −6.6 (10.8) mm Hg.