Vitamin D deficiency has been reported in several cultures and regions, including the Middle East, North Europe, and Australia. In this review, we summarize and discuss existing studies on factors underlying vitamin D deficiency across different regions. In particular, we explain key roles played by lifestyle, including sun exposure, season change, diet, and clothing (concealing vs. non-concealing) as factors leading to vitamin D deficiency. We further discuss gender differences in vitamin D levels and, the impact of vitamin D supplements on cognition. The introductory section of this paper focuses on introducing vitamin D deficiency and highlighting the prevalence of vitamin D deficiency in Eastern countries. Here, we also provide a comparative literature analysis not only based on Eastern and Western countries but also compare the prevalence of vitamin D deficiency between males and females. Our review provides key information on potential life changes that help increase vitamin D and protect against the development of several disorders
