Forget sunshine, you need a vitamin D supplement

Posted on Sun, 3 Oct 10

Vitamin D deficiency is remarkably common and linked to the development of several chronic diseases including common cancers, autoimmune, cardiovascular, and infectious diseases (1). Although vitamin D is made from sunlight a dietary supplement is the safest, most effective way to ensure you get enough vitamin D.

Sunshine is not enough  

It has long been suggested that 5 to 15 minutes of sun exposure to the hands, face, and arms 2 to 3 times a week in the northern latitudes is sufficient to ensure adequate vitamin D. However the studies used to come to this conclusion are flawed. In the real world there are several important factors affecting vitamin D synthesis.

If this much sun were enough to achieve optimal vitamin D levels it would be unlikely that vitamin D deficiency was common in areas with plenty of sunshine such as Hawaii, rural India, rural Brazil, southern Arizona, southern Florida, and Queensland, Australia. But it is.

Why you are deficient

Reasons for widespread vitamin D deficiency, even in areas of high sun exposure, are that factors such as cloud cover, ozone concentrations, air pollutants, altitude, season of the year, and time of day, as well as by variation in skin pigmentation affect our ability to synthesise vitamin D.

In addition obesity, which affects a significant percentage of the general population, is associated with lower serum vitamin D, reduced ability to synthesise vitamin D and perhaps a lower response to supplementation. Also it is well known that the elderly have up to one-fifth of the ability to synthesise vitamin D. And a wide variability amongst individuals to sun exposure and supplementation suggests that there may be other factors, yet undiscovered, that affect vitamin D status.

How much vitamin D do you need?

Taking these factors into account leading experts suggest that sun exposure “is not the best source for assuring maintenance of optimal vitamin D status (2)” and that “oral supplements of vitamin D would probably represent the safest way to increase vitamin D status (3).”

A daily amount of 800-1000IU of Vitamin D will satisfy your body’s basic requirement and higher doses are needed to correct deficiency. To boost your levels leading advocates recommend you take 5,000 IU of Vitamin D3 per day for 2–3 months, then obtain a 25-hydroxyvitamin D test and adjust your dosage so that blood levels are between 50–80 ng/mL (or 125–200 nM/L) year-round (4).

References:

1. Holick MF. Vitamin D: a D-Lightful health perspective. Nutr Rev. 2008 Oct;66(10 Suppl 2):S182-94.

2. 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.

3. 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.

4. The Vitamin D Counsil. Understanding Vitamin D Cholecalciferol. www.vitamindcouncil.org. Accessed online at 26-04-2010