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).
References:
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.