Lee Swanson Research Update

Supplements Beat Sun for Vitamin D Boost

July 2010

Adequate vitamin D levels are best achieved by supplements because of the side-effects of ultraviolet (UV) exposure, say the results of a new computer simulation model from the U.S.

The body produces vitamin D in the skin on exposure to sunlight, but the merits of getting vitamin D via sunlight or from supplements is a source of ongoing debate. In the U.S., where over 1.5 million people are diagnosed with skin cancer every year, experts are pushing supplements, claiming recommendations for sun exposure are "highly irresponsible."

Scientists from the Memorial Sloan-Kettering Cancer Center in New York and the Norwegian Institute for Air Research in Tromsø, Norway, used a computer model to determine optimal sun exposure times to produce blood levels of vitamin D3 equivalent to 400 or 1,000 IU of vitamin D.

The researchers chose two geographical sites—Miami, FL and Boston, MA—for their simulation and selected four months—January, April, July and October.

Data showed that in summer in Boston, people would need between three and eight minutes of sunlight exposure to about 25% of their body surface to synthesize 400 IU of vitamin D. In winter, the simulation indicated that it would be difficult to produce any vitamin D in Boston. No such problems were calculated in Miami, however, with between three and six minutes needed to produce 400 IU at all times of the year.

"There are many limitations to these models, and clearly the estimates are only rough approximations," the researchers said. "Although it may be tempting to recommend intentional sun exposure for a few minutes several times a week, cutaneous vitamin D synthesis is an intricate process and depends on numerous variables.

"Even in a simplified model such as the one used here, it can be seen to vary considerably by geography, season and skin type. Furthermore, even if a more accurate and practical model were developed, titrating one’s own exposure to sunlight is difficult, if not impossible.

"Because of these practical difficulties combined with the detrimental side-effects of UV exposure, we endorse the IARC assessment that even if it is ultimately demonstrated that increasing vitamin D levels impacts chronic disease, oral supplements of vitamin D would probably represent the safest way to increase vitamin D status," the researchers concluded.

An ever-growing body of science supports the benefits of maintaining healthy vitamin D levels. In adults, it is said vitamin D deficiency may precipitate or exacerbate osteopenia, osteoporosis, muscle weakness, fractures, autoimmune diseases, infectious diseases and cardiovascular diseases.

Journal of the American Academy of Dermatology 62(6): 935-936, 2010

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