Abstract
It is estimated that approximately 1 billion people worldwide have blood concentrations of vitamin D that are considered suboptimal. Much research has been conducted over the past 30 years linking low vitamin D serum concentrations to both skeletal and nonskeletal conditions, including several types of cancers, cardiovascular disease, diabetes, upper respiratory tract infections, all-cause mortality, and many others. Several observational studies and a few prospectively randomized controlled trials have demonstrated that adequate levels of vitamin D can decrease the risk and improve survival rates for several types of cancers including breast, rectum, ovary, prostate, stomach, bladder, esophagus, kidney, lung, pancreas, uterus, non-Hodgkin lymphoma, and multiple myeloma. Individuals with serum vitamin D concentrations less than 20 ng/mL are considered most at risk, whereas those who achieve levels of 32 to 100 ng/mL are considered to have sufficient serum vitamin D concentrations. Vitamin D can be obtained from exposure to the sun, through dietary intake, and via supplementation. Obtaining a total of approximately 4000 IU/d of vitamin D3 from all sources has been shown to achieve serum concentrations considered to be in the sufficient range. Most individuals will require a dietary supplement of 2000 IU/d of vitamin D3 to achieve sufficient levels as up to 10 000 IU/d is considered safe. Vitamin D3 is available as an over-the-counter product at most pharmacies and is relatively inexpensive, especially when compared with the demonstrated benefits.