Prevalence of vitamin D deficiency in healthy adults: A systematic review and meta-analysis

Research shows that vitamin D deficiency is increasing worldwide and has become an important public health issue. Vitamin D deficiency is an independent risk factor for mortality in the general population and plays a role in the etiology of various diseases, including cancer, heart diseases, fractures, autoimmune diseases, influenza, type 2 diabetes, and depression. The aim of this study is to estimate the prevalence of vitamin D deficiency among healthy adults worldwide through systematic review and meta-analysis from 2003 to 2023. Procedures in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed, and a International Prospective Register of Systematic Reviews registration was established. Literature searches were conducted using four different databases. The prevalence of vitamin D deficiency in healthy adults worldwide was % 51,1. This rate was % 56,8 in women and % 43,8 in men. In the African region, the prevalence of vitamin D deficiency is estimated to be % 54,2, with this rate being % 61,6 among healthy adult women. In the American region, the overall prevalence of vitamin D deficiency is % 34,3, with % 33,5 in women and % 30,7 in men. In Europe, the overall prevalence is % 51,6, with % 60,5 in women and % 52,8 in men. In the Western Pacific region, % 44,9, with % 55,3 in women and % 33,5 in men. In the Eastern Mediterranean, vitamin D deficiency the overall prevalence is % 62,1, % 62,7 in women and % 49,3 in men. In Southeast Asia, the overall prevalence is % 55,3, with % 58,8 in women and % 53,0 in men. Generally, the lowest prevalence of vitamin D deficiency is observed in America, where one in three individuals is found to be deficient. Vitamin D deficiency is found at higher rates in women compared to men, particularly reaching the highest prevalence of % 62,7 in Eastern Mediterranean. These findings indicate that each region needs to develop its own unique strategies. Public health measures such as increasing sun exposure and vitamin D supplementation may be effective in combating deficiencies. International and local health organizations need to conduct education and awareness campaigns on this issue. Keywords: Vitamin D deficiency, adults, prevalence, systematic review, and meta-analysis.