The US government currently recommends a daily intake of 400IU (International Units) for vitamin D. Both the US government and the European Union have the "tolerable upper intake limit" set at 2000IU. However, in recent years many experts have concluded that both of these levels are far too low. Feeding this controversy, research conducted by the industry trade group, Counsel for Responsible Nutrition found the upper limit could be raised to 10,000 UI.
Two new cancer meta-analysis studies provide more evidence in support of raising the daily intake level for vitamin D. The first of the two studies was published in the American Journal of Preventative Medicine. The study reviewed five colorectal cancer studies with a total of 1448 individuals, all Caucasian. Serum (blood) vitamin D levels of the individuals were evaluated and divided into quartiles. The quartiles where then compared to assess relative risk. The researchers found that those in the highest quartile, with serum Vitamin D levels greater than or equal to 33 ng/ml (nanogram per milliliter), had a 50% lower risk of colorectal cancer than those in the lowest quartile of serum Vitamin D levels, less than or equal to 12 ng/ml. Researchers went on to conclude that if serum vitamin D levels were increased to even greater levels than those found in the study, to 46 ng/ml, colorectal cancer could be reduced by 66%.1
The authors concluded "the evidence to date suggests that daily intake of 1000-2000 IU per day of vitamin D3 could reduce the incidence of colorectal [cancer] with minimal risk."
The second of the two studies, which examined vitamin D level and breast cancer risk, was recently published in the online edition of the Journal of Steroid Biochemistry and Molecular Biology. The study pooled results from two other studies and, as in the colorectal cancer study, subjects were divided into quartiles based on serum vitamin D content. Again relative risk was determined by comparing those in the lowest quartile of serum vitamin D to those in the highest quartile of serum vitamin D. While the range was greater than in the first study, with the lowest quartile of vitamin D being 10 ng/ml or less and the highest being 50 ng/ml or greater, the outcome was similar. The researchers found that those in the highest quartile had a 50% lower risk of breast cancer when compared to those in the lowest quartile.2
The researchers noted that a 50 ng/ml serum level "could be achieved by oral intake of 2000IU per day and, if appropriate and climate allowing, about 12 minutes per day in the noontime sun on a clear day with 50 percent of the skin exposed to the sun."
Learn more about Vitamin D3 and its potential benefits, and read articles on the latest studies here.
- Gorham, Garland, et al. (2007). "Optimal Vitamin D Status for Colorectal Cancer Prevention." American Journal of Preventive Medicine 32(3): 210-216.
- Garland, C. F., E.D. Gorham, S.B. Mohr, W.B. Grant, E.L. Giovannucci, M. Lipkin, H. Newmark, M.F. Holick, F.C Garland (2006). "Vitamin D and prevention of breast cancer: Pooled analysis." Journal of Steroid Biochemistry and Molecular Biology doi: 10.1016/j.jsbmb.2006.12.007.
