Since 1998, Grassroots, a non-profit community service organization dedicated to promoting public awareness about Vitamin D3 collected data on over 3,600 study participants. The mean age of participants was 53.3+/-13.4 years. Every participant had their Vitamin D3 level assessed every six months along with details on the dose of Vitamin D supplements being taken. Vitamin D3 level results were returned to the participants who were then able to modify their dose to achieve maximum blood levels.
To date epidemiological data suggests that the anticancer effect of Vitamin D3 occurs when blood levels are greater than 40ng/ml. Therefore, the aim of this study was to determine what dose of Vitamin D3 is necessary to achieve blood levels between 40-60ng/ml.
Approximately 25% of the participants did not take any Vitamin D3 supplements, while 47% took up to 2000IU per day, 1.8% took over 10,000IU and the majority took up to 5000IU per day.
Despite taking as much as 10,000IU Vitamin D3 per day, no participant in the study demonstrated Vitamin D3 levels in the toxic range of >200ng/ml. For those severely deficient in Vitamin D3, each 1000IU of increased supplementation resulted in an increase of 10ng/ml in Vitamin D3 blood levels. Those with existing blood levels above 30ng/ml demonstrated an 8ng/ml increase in blood level for every 1000IU given, and those with existing levels above 50ng/ml showed an increase of only 5ng/ml for every 1000IU of Vitamin D3. This demonstrates how difficult it would be to take enough Vitamin D3 to reach toxic levels. As blood levels increase, absorption decreases.
Perhaps the most surprising finding was the dose of Vitamin D3 necessary to ensure that 95.7% of the population achieved levels of >40ng/ml was 9,600IU. Although such doses are an order of magnitude higher than those currently recommended, these calculated daily intakes are of the same magnitude as produced by a single dose of UV-B radiation achieved during a few minutes of solar UVB exposure near noon in midsummer, assuming nearly complete skin exposure.
Once again, these results demonstrate the importance of actually measuring blood levels of Vitamin D3 to ensure that the dose taken is adequate to achieve optimal blood levels.
The complete study report can he accessed here.
1) Vitamin D Supplement Doses and Serum 25-Hydroxyvitamin D in the Range Associated with Cancer Prevention Anticancer Research February 2011 vol. 31 no. 2 607-611 Heaney, Robert.
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