The Institute of Medicine (IOM) recommends a mere 600 IUs of vitamin D per day for adults. As pointed out in a 2014 paper,2 the IOM underestimates the need by a factor of 10 due to a mathematical error, which has never been corrected.

A large number of studies have shown raising your vitamin D level can significantly reduce your risk of cancer. Most recently, a randomized clinical trial5 by researchers at Creighton University, funded by the National Institutes of Health (NIH), found vitamin D and calcium supplementation lowered participants’ overall cancer risk by 30 percent.6,7,8

Previous research has shown that once you reach a serum vitamin D level of 40 ng/mL, your risk for cancer diminishes by 67 percent, compared to having a level of 20 ng/ml or less.9,10,11,12,13,14,15,16

Most cancers, they found, occurred in people with a vitamin D blood level between 10 and 40 ng/mL. The optimal level for cancer protection was identified as being between 40 and 60 ng/mL.