Vitamin D Supplementation and Sunlight Exposure on Serum Vitamin D Concentrations in 2 Parallel, Double-Blind, Randomized, Placebo-Controlled Trials

• Published in: The Journal of nutrition Vol. 151; no. 10; pp. 3137 - 3150
• Main Authors: Mendes, Marcela M, Hart, Kathryn H, Williams, Emma L, Mendis, Jeewaka, Lanham-New, Susan A, Botelho, Patrícia B
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.10.2021; American Institute of Nutrition
• Subjects: Adult; Brazil; Calciferol; Cholecalciferol; Diaries; Diet; Dietary intake; Dietary Supplements; Dosimeters; Double-Blind Method; Double-blind studies; England; Exposure; Female; Food intake; High-performance liquid chromatography; Humans; latitude; Liquid chromatography; Nutrition; Nutrition research; Parathyroid; Parathyroid hormone; Placebo effect; Placebos; Seasons; serum 25(OH)D; Sunlight; supplementation; Tandem Mass Spectrometry; Temperature effects; Vitamin D; Vitamin D Deficiency - prevention & control; Young Adult; UVB; RCT; D-SOL study; PTH; vitamin D; IOM; latitude; supplementation; England; ITT; IU; sunlight; serum 25(OH)D; Brazil; 25(OH)D
• ISSN: 0022-3166; 1541-6100
• DOI: 10.1093/jn/nxab209

Vitamin D concentrations are a function of sunlight exposure and dietary intake. However, current dietary vitamin D recommendations do not consider differences in country-specific sunlight availability or spontaneous individual exposure. We aimed to investigate the effects of vitamin D supplementation and sunlight exposure on vitamin D concentrations in Brazilian women living in high compared with low latitudes. In 2 parallel, double-blind, randomized placebo-controlled trials, Brazilian women living in England (51°N) composed “without ultraviolet B (UVB) exposure” groups and those living in Brazil (16°S) composed the “with UVB exposure” groups (mean age, 31.39 ± 8.7 years). Participants received 15 μg cholecalciferol or placebo daily for 12 weeks during wintertime. Serum 25-hydroxyvitamin D [25(OH)D] concentrations, the primary outcome, were assessed by HPLC-MS/MS, vitamin D intakes were assessed by 4-day diet diaries, and sunlight exposure was assessed by UVB dosimeters. The effects of supplementation and UVB exposure were tested by the intention to treat with a linear mixed model. The 25(OH)D concentrations increased in both supplemented groups [from 75.1 ± 22.0 to 84.8 ± 21.0 nmol/L (P = 0.004) in the group with UVB exposure; from 38.1 ± 15.9 to 55.1 ± 12.2 nmol/L (P < 0.001) in the group without UVB exposure], with no significant changes in either placebo group. Concentrations in both supplemented groups were higher than those in the placebo group without UVB exposure (P = 0.0002 in the group with UVB exposure; P = 0.0035 in the group without UVB exposure). Postintervention 25(OH)D concentrations were significantly affected by serum 25(OH)D concentrations at baseline (P < 0.0001) and by intervention (placebo or supplement; P > 0.0001), with a large effect size (Cohen's D = 0.768), but were not affected by UVB exposure (with or without; P = 0.1386), nor by the interaction between the intervention (placebo or supplement) and UVB exposure (with or without; P = 0.9845). Moderate supplementation of 15 ug/d cholecalciferol, in accordance with current recommendations, supports an adequate vitamin D status in adult women, irrespective of latitude, and might concomitantly prevent an increase in parathyroid hormone. The Interaction Between Vitamin D Supplementation and Sunlight Exposure in Women Living in Opposite Latitudes (D-SOL) study was registered at clinicaltrials.gov as NCT03318029.