Incremental Cholecalciferol Supplementation up to 15 μg/d Throughout Winter at 51–55° N Has No Effect on Biomarkers of Cardiovascular Risk in Healthy Young and Older Adults 1–5

Two separate, identical, double-blind, randomized, placebo-controlled intervention studies were carried out in the south and north of Ireland (51–55°N). Men and women aged 20–40 y (n = 202) and ≥64 y (n = 192) received cholecalciferol at doses of 0 (P), 5 (D3–5), 10 (D3–10), or 15 (D3–15) μg/d (0–600 IU) during wintertime. Serum 25-hydroxyvitamin D [s25(OH)D], intact parathyroid hormone, systolic and diastolic blood pressure, fasting lipids, glucose and insulin, HOMA-IR, high-sensitivity CRP, matrix metalloproteinase-9, and its inhibitor (tissue inhibitor metalloproteinase-1) were measured at baseline (October) and 22 wk later at endpoint (March). Vitamin D receptor Fok I and Taq I genotypes were analyzed and dietary intakes of vitamin D and calcium were assessed. In young adults, s25(OH)D decreased from baseline to endpoint (P < 0.001), except in the D3–15 group, who maintained the baseline concentration of ~70 nmol/L. Older adults had lower s25(OH)D at baseline (median, 54.2 nmol/L) and concentrations increased in the D3–10 and D3–15 groups (P < 0.001). There were no significant effects of supplementation on cardiovascular disease (CVD) risk biomarkers in either age group. Fasting glucose and total and HDL cholesterol were lower (P < 0.05) in older adults with the Fok 1 ff genotype than in those with FF or Ff. Putative effects of vitamin D on cardio-metabolic health will only be evident at higher intakes than the current RDA and possibly in individuals at particular risk of low s25(OH)D and/or CVD risk.