Vitamin D Supplementation and Genetic Polymorphisms Impact on Weight Loss Diet Outcomes in Caucasians: A Randomized Double-Blind Placebo-Controlled Clinical Study

Abstract

Vitamin D deficiency or insufficiency is common in obese people, with some studies suggesting that low vitamin D level might be an independent predictor of obesity. Thus, the purpose of the present randomized, double-blind, placebo-controlled study was to investigate the effect of oral spray vitamin D₃ 3000 IU supplementation along with personalized weight-loss diet on obesity markers in overweight and obese Caucasians with vitamin d deficiency or insufficiency. The impact of vitamin D receptor (VDR) and adrenergic receptors (ADRs) genetic variants on vitamin D levels and weight loss diet outcomes was also investigated. After signing informed consent, a total of 125 eligible volunteers were randomly assigned into vitamin D (vitamin D₃ 3000 IU/d oral spray supplementation, <i>n</i> = 76) or placebo (xylitol, water, mint, <i>n</i> = 49) group following a weight loss program (600 calories less than the total energy expenditure of each volunteer) for 3 months. Fat mass, BMI, REE and 25(OH)D serum level were monitored on baseline and each month. DNA samples were extracted from buccal swabs and genotyped for the rs2228570 (<i>VDR</i>), rs1544410 (<i>VDR</i>), rs731236 (<i>VDR</i>), rs1800544 (<i>ADRA2A</i>), rs1801252 (<i>ADRB1</i>), rs1042713 (<i>ADRB2</i>), and rs4994 (<i>ADRB3</i>) polymorphisms. Statistical analysis was performed using SPSS package (v.23). Between group comparisons revealed significant improvement in serum 25(OH)D level and greater reduction in weight, BMI and fat percentage in the vitamin D group compared to placebo group (<i>p</i> < 0.05). In the vitamin D group, carriers of the rs2228570 T allele tended to have greater vitamin D level improvement compared with the homozygous C allele (<i>p</i> = 0.067). Furthermore, heterozygous (CT) for the rs731236 tended to have lesser weight loss (<i>p</i> = 0.068) and for the rs1042713, a lower decline in fat percentage was observed for homozygous AA carriers compared to the heterozygous (<i>p</i> = 0.051). In the control group, differences in weight loss (<i>p</i> = 0.055) and BMI (<i>p</i> = 0.045) were observed between rs1544410 AA and GG homozygous. In conclusion, vitamin D oral spray supplementation seems to improve vitamin D status and decrease obesity markers during a weight-loss intervention in overweight/obese Caucasians with vitamin D deficiency or insufficiency. Also, the results of the present study indicate that <i>VDR</i> and <i>ADRs</i> genetic polymorphisms seem to influence vitamin D supplementation response and obesity markers.