How much is enough? (Louise McCoy/The Epoch Times)
For the last few months, I have been attempting to optimize my own vitamin D levels. Earlier in the year, I had my levels measured for the first time ever and these came back at 15 ng/ml (very low). I started supplementing with vitamin D at a dose of 3,000 IU per day and about 10 weeks later, my levels had increased to 31 ng/ml. The 3,000 IU I was taking was roughly twice what I theoretically needed to maintain this level of vitamin D [1]. Perhaps my need for vitamin D was greater than others? Reading a letter published online in the American Journal of Clinical Nutrition this week, I’m not so sure.
In this letter [2], Dr Reinhold Vieth from Mount Sinai hospital in Toronto criticizes the mathematical extrapolation on which previous research [1] was based. Dr Vieth claims that this inappropriate methodology has led to an underestimation of vitamin D requirements. In support of this he cites three studies (two are his own) in which individuals were actually supplemented with vitamin D to see what blood levels were achieved [3–5]. According to this research (in both younger and older adults), to maintain a blood level of 32 ng/ml requires 4,000 IU (100 micrograms) of vitamin D per day.
These levels are much more in line with my own, recent experiences. But much more importantly, they again demonstrate that the traditionally recommended vitamin D levels are quite inadequate. Four thousand IU per day is 10 times the amount usually recommended, and this is to achieve a blood level that some would stay is still a way off optimal.
References:
1. Cashman KD, et al. Estimation of the dietary requirement for vitamin D in healthy adults. American Journal of Clinical Nutrition, 2008; 88:1535–1542.
2. Vieth R. Experimentally observed vitamin D requirements are higher than extrapolated ones. American Journal of Clinical Nutrition, Aug. 26, 2009 [Epub ahead of print publication]
3. Vieth R, et al. Randomized comparison of the effects of the vitamin D3 adequate intake versus 100 micrograms (4,000 IU) per day on biochemical responses and the wellbeing of patients. Nutrition Journal, 2004; 19; 3:8.
4. Vieth R, et al. Efficacy and safety of vitamin D3 intake exceeding the lowest observed adverse effect level. American Journal of Clinical Nutrition, 2001; 73(2): 288–94.
5. Mocanu V, et al. Long-term effects of giving nursing home residents bread fortified with 125 micrograms (5,000 IU) vitamin D(3) per daily serving. American Journal of Clinical Nutrition, 2009; 89(4): 1132–7.
Dr. John Briffa is a London-based physician and health writer with an interest in nutrition and natural medicine. His Web site is drbriffa.com
