Exposure to sunlight or ultraviolet-B radiation (UVB) can provide a person their entire daily requirement of vitamin d because it stimulates the production of vitamin D3 (Linus Pauling Institute). Exposing the body in a bathing suit to sunlight to a point that causes pink skin is called 1 minimal erythemal dose (MED) and can produce 10,000 to 25,000 iu of vitamin d. For a daily dose of vitamin d of 600 to 1000 iu, only 6% of the body needs to be exposed to 1 MED. Adequate vitamin d requirements can be met with 1 MED of sun exposure to exposed skin three times a week. However in order to treat vitamin d deficiencies, it is best to use large pharmacologic doses for short periods of time (Holick, 2002). Research shows that vitamin D3 is more bio-available than vitamin D2 in large bolus doses. There is no difference in bio-availability when given daily (Linus Pauling Institute).
Other interesting facts about vitamin d:
- The ability to synthesize vitamin d3 in a light-skinned person, is 5-10 fold more efficient than in a dark-skinned individual (Chen, et al., 2007).
- Vitamin d is a hormone, not a vitamin (Holick, 2002).
- Only a few foods naturally contain vitamin d, such as salmon (Holick, 2002).
- Vitamin D is removed more efficiently from circulation in people with high body fat content (Holick, 2002).
Chen, T. C., Chimeh, F., Lu, Z., Mathieu, J., Person, K. S., Zhang, A., Kohn, N., Martinello, S., Berkowitz, R., & Holick, M. F. (2007). Factors that influence the cutaneous synthesis and dietary sources of vitamin D. Archives of Biochemistry and Biophysics, 460(2), 213–217. https://doi.org/10.1016/j.abb.2006.12.017
Holick, M. F. (2002). Vitamin D: the underappreciated D-lightful hormone that is important for skeletal and cellular health. Current Opinion in Endocrinology & Diabetes, 9(1), 87–98. https://doi.org/10.1097/00060793-200202000-00011
Linus Pauling Institute. (n.d.). Micronutrient Information Center: Vitamin D. Oregon State University. https://lpi.oregonstate.edu/mic/vitamins/vitamin-D#mechanisms-function
*These statements are not meant to diagnose or treat. You should consult your health care provider before starting any new diet, exercise, or supplement.