Until just a few years ago, it was thought that vitamin D is only needed for building and maintain strong bones.
However, over the past decade an impressive body of scientific research has demonstrated the importance of optimal vitamin D status for wide array of health conditions.
Vitamin D is interesting for several reasons:
1. The role of vitamin D for health promotion has undergone a paradigm shift. Adequate vitamin D levels are necessary to prevent many diseases, especially cardiovascular disease (including high blood pressure), endothelial dysfunction, diabetes (both type1 and type-2), the metabolic syndrome, muscle weakness, cancer, chronic inflammation, osteoporosis (including falls and fractures), cognitive dysfunction and mental illness, autoimmune diseases (e.g. multiple sclerosis, rheumatoid arthritis), infectious diseases, as well as infertility and adverse pregnancy and birth outcomes [1-26].
Vitamin D deficiency/insufficiency is associated with increased all-cause mortality [1, 27], and vitamin D supplementation has been shown to decrease mortality [28, 29]. It has been estimated that doubling blood vitamin D levels in the general population (from 21 ng/mL to 44 ng/mL) would reduce vitamin D-related disease mortality rate by 20%, and increase life expectancy with about 2 years .
2. Insufficient levels of vitamin D also have direct implications for fitness enthusiasts and athletic performance, due to the importance of vitamin D for muscle function (I will cover this in much more depth in an upcoming article) [31-42].
3. In contrast to most other vitamins, vitamin D deficiency/insufficiency is very common (more on that below).
4. The vitamin D requirement for health promotion and protection against all-cause mortality and muscle dysfunction is much higher than the dietary recommendations (RDA), which only consider for bone related outcomes [4, 43-48].
Having heard about all the vitamin D benefits you might wonder what is the optimal vitamin D blood level? How low is too low? How common is vitamin D deficiency or insufficiency?