What is the right vitamin D dosage?
This article is about getting the right vitamin D dosage to take advantage of those benefits of vitamin D you've read about elsewhere on this site. This is one case where the science is moving much faster than government agencies have been able to keep track of. As a result, getting 100% of your daily vitamin D intake is enough to make sure your bones stay in one place, but does little else.
Vitamin D Dosage: An Evolutionary Perspective
Humans evolved in equatorial east Africa, and our genes have not changed much since then. Our bodies, therefore, have adapted to receive enormous doses of vitamin D from the sun's action on our skin. The typical pre-historical human probably had 5-6 times as much calcipherol (vitamin D's main metabolite) in circulation than the average resident of London or Stockholm (1). Does this mean everyone who doesn't live in equatorial latitudes is deficient in vitamin D? Yes and no. No because people have survived at northern latitudes for centuries without supplements. But yes because there are well-defined
linked to low sun exposure, high latitude, and low vitamin D status (2).
Vitamin D Dosage: How much do you need?
This question has been under furious debate for the last 15 years. The emerging answer is that you need more than the recommended 400 IU/day. The answer will also vary depending on how much sun exposure you get, and the color of your skin. Darker skinned people, in general, need quite a bit more vitamin D because of the natural sunblock effects of pigmentation. Regardless, studies in both Europe and the US agree that non-outdoor workers need more vitamin D than they are getting (3,4).
A key paper in the field has helped to define what kinds of intakes are necessary to avoid declining vitamin D status during the winter. Heaney and coworkers at Creighton University in Nebraska looked at the vitamin D levels of healthy caucasian men during the winter (5). The researchers found that a vitamin D dosage of 25 mcg (or 1000 IU) was needed just to keep a steady serum level. Further calculations indicated that an average person taking the "recommended dose" of vitamin D and not getting much sun could easily wind up vitamin D levels deep into unhealthy territory.
Vitamin D Dosage: Down to specifics
In addition to a multivitamin and a calcium+D supplement, I take a 1000 IU vitamin D3 supplement, giving about 1700 IU/day. During cloudy, winter months, I take two 1000 IU pills a day. I recommend most people who don't spend lots of time outdoors to do the same. A fascinating paper by Bischoff-Ferrari shows a clear correlation between higher serum calcipherol concentrations (a stable vitamin D metabolite) at colon cancer (6). Optimal protection comes from getting doses above 700-800 IU/day, along with some sun.
Another unappreciated issue is Vitamin D2 or D3? The research is very clear that vitamin D3 is more readily absorbed by the body, so I recommend that (7). Of course, if you are a strict vegitarian or vegan, you should know that vitamin D3 comes from animals (usually fish) and vitamin D2 is the way to go for you. Actually, if you do not eat meat, I would recommend getting 15-30 min of sun without sunblock (except maybe on your face) twice a week. This is the most reliable way to get your vitamin D stores topped up.
Find out about the group that especially needs to up their vitamin D dosage
1. Vieth, R. "What is the optimal vitamin D status for health?" Progress Biophys Mol Biol. 92 (2006) 26-32.
2. Grant, WB. "Epidemiology of disease risks in relation to vitamin D insufficiency." Prog Biophys Mol Biol. 92 (2006) 65-79.
3. Chapuy, MC, Preziosi, P, Maamer, M, et al. "Prevalence of vitamin D insufficiency in an adult normal population," Osteoporos Int. 7 (1997) 439-43.
4. Hanley, DA, Davison, KS. "Vitamin D insufficiency in North America." J Nutr. 135 (2005) 332-7.
5. Heaney RP, Davies, KM, Chen, TC, et al. "Human serum 25-hydroxycholecalciferol response to extended oral dosing with cholecalciferol." Am J Clin Nutr. 77 (2003) 205-10.
6. Bischoff-Ferrari, HA, Giovannucci, E, Willett, WC, et al. "Estimation of optimal serum concentrations of 25-hydroxyvitamin D for multiple health outcomes." Am J Clin Nutr. 84 (2006) 18-28.
7. Trang, HD, Cole, DEC, Rubin, LA, et al. "Evidence that vitamin D3 increases serum 25-hydroxyvitamin D more efficiently than does vitamin D2." Am J Clin Nutr. 68 (1998) 854-8.