Association between childhood obesity and vitamin D: A Mendelian randomization study

Abstract Background This study evaluated the causal relationship between childhood obesity and vitamin D levels by performing a Mendelian randomization (MR) analysis using publicly available genome‐wide association study (GWAS) summary statistics. To mitigate bias stemming from confounding and reverse causation, we conducted an MR analysis to assess the causal impact of childhood obesity on the major circulating form of vitamin D, 25‐hydroxyvitamin D (25(OH)D). Methods Vitamin D is present in the blood in the form of 25(OH)D; childhood obesity and 25(OH)D levels data were obtained from the IEU open GWAS project, which were subjected to MR analyses. The IVW method was used as the predominant analysis method and was complemented by MR‐Egger, simple mode, weighted median, and weighted mode methods. The MR‐PRESSO method was utilized to identify horizontal pleiotropy and potential outliers. Results This study indicated that childhood obesity affects the serum of 25(OH)D, which was significant in the IVW (OR [95%CI], 0.977 [0.966–0.989], p = 0.0001), and weighted‐median (OR [95%CI], 0.983 [0.969–0.997], p = 0.015) analyses, but nonsignificant in the MR‐Egger (OR [95%CI], 0.985 [0.897–1.082], p = 0.784), simple mode (OR [95%CI], 0.985 [0.965–1.005], p = 0.233), and weighted mode (OR [95%CI], 0.985 [0.967–1.004], p = 0.214) analyses. Conclusions In summary, we found a potential inverse association between elevated childhood obesity and 25(OH)D levels, which suggested that obese children need to pay attention to their 25(OH)D levels, and vitamin D supplementation may be necessary when needed.