Pooling data from 17 observational studies, an international team of researchers found the lowest risk of colorectal cancer in people with blood levels of vitamin D between 30 and 40 ng/mL (75 to 100 nmol/L); beyond that, risk didn’t continue to decline. The apparent benefit was stronger in women than in men. The researchers controlled for body weight, physical activity, and known risk factors for colorectal cancer.
According to the Institute of Medicine (now called the National Academy of Medicine), blood levels above 20 ng/mL are sufficient for bone health, but many experts believe that 30 ng/mL or higher is a better goal for bone and general health. This was observational research and couldn’t prove causality; several major clinical trials on vitamin D are underway.
This article first appeared in the UC Berkeley Wellness Letter.