Food and sunlight are not good sources of vitamin D

Posted on Mon, 16 Apr 12

There is a lot of confusion and controversy around Vitamin D deficiency, but one thing that is quite clear is that vitamin D rich foods and sunlight are not enough to ensure you are getting sufficient vitamin D.

Food is not a good source of vitamin D

The single reason for widespread vitamin D deficiency is lack of adequate sunlight. Food is not a sufficient source of vitamin D. To meet the popular recommendation of 2000 IU of Vitamin D a day you would need to eat 2-4 daily servings of the richest food source of vitamin D available; wild (not farmed) salmon (1). Unless you are a grizzly bear, that is a lot of salmon. Fortification of foods could change this but in most countries vitamin D levels in fortified foods are negligible (2).

For most people sunlight exposure is not enough

Modern humans evolved in equatorial Africa where we wandered around outside naked in the sun (our naked skin is where we synthesise vitamin D from sunlight). Today people living in far northern and southern latitudes cannot make vitamin D for roughly 6 months of the year and during summer months a high amount of time is spent indoors. Some outdoor-working adults may make enough vitamin D but these people represent a small minority of the population (3).

Supplements are safe and effective 

Taking these factors into account leading experts suggest that sun exposure “is not the best source for assuring maintenance of optimal vitamin D status (4)” and that “oral supplements of vitamin D would probably represent the safest way to increase vitamin D status (5).”

Find out more here.

References:

1. 1. Holick MF, Chen TC. Vitamin D deficiency: a worldwide problem with health consequences. Am J Clin Nutr. 2008 Apr;87(4):1080S-6S.
   2. Gillie, O. Sunlight robbery: Vitamin D and public health – Is current UK public health policy on vitamin D fit for purpose? Caroline Walker Trust. November 16, 2010.
   3. Godar DE, Pope SJ, Grant WB, Holick MF. Solar UV doses of adult Americans and  vitamin D(3) production. Dermatoendocrinol. 2011 Oct;3(4):243-50.
   4. Tsiaras WG, Weinstock MA. Commentary: Ultraviolet irradiation and oral ingestion as sources of optimal vitamin D. J Am Acad Dermatol. 2010 Jun;62(6):935-6.
   5. Terushkin V, Bender A, Psaty EL, Engelsen O, Wang SQ, Halpern AC. Estimated equivalency of vitamin D production from natural sun exposure versus oral vitamin D supplementation across seasons at 2 US latitudes. J Am Acad Dermatol 2010;62:929-34.