Abstract
Obesity and vitamin D deficiency are associated with risk for several cancers, possibly through inflammation and adipokine-related pathways. Two hundred and eighteen postmenopausal women with BMI > 25 kg/m(2) and low serum 25-hydroxyvitamin D (25(OH)D; ≥10-<32 ng/mL), were randomized to 12 months of either (i) weight-loss intervention + 2000 IU/day oral vitamin D3 or (ii) weight-loss intervention + daily placebo. Serum adiponectin, leptin, TNFα, IL6, IL1β, IL8, and IL10, were measured by immunoassay, and a composite inflammatory biomarker score calculated. Using generalized estimating equations, mean changes in outcomes were compared between arms (intent-to-treat), adjusted for possible confounders. Analyses were also stratified by weight-loss (gained/no weight-loss; <5%; 5% to 10%; ≥10%). At 12 months, there were no significant differences in analyte changes between arms. In stratified analyses, participants randomized to vitamin D3 who lost 5% to 10% of baseline weight, versus participants who gained weight/had no weight-loss, had significantly greater decreases in levels of IL6 compared with those randomized to placebo: absolute change -0.75 pg/mL (-17.2%), placebo versus -1.77 pg/mL (-37.3%), vitamin D, P = 0.004. Similar but attenuated results were observed for participants who lost ≥10% of baseline weight: -0.41 pg/mL (-13.6%), placebo versus -0.67 pg/mL (-17.3%), vitamin D, P = 0.02. Effects of vitamin D3 supplementation on levels of IL1β were inconsistent when stratified by weight loss. There were no intervention effects on IL10, TNFα, IL8, the composite score, adiponectin, or leptin, when stratified by weight-loss. In conclusion, vitamin D3 supplementation in combination with weight-loss of at least 5% of baseline weight was associated with significant reductions in levels of IL6.