The results of a landmark study that evaluated the impact of Vitamin D on cancer in 25,871 people was just published!

I recently posted a blog titled, Does Vitamin D have a protective effect against cancer?”

My short answer to this question was “We don’t know!” Due to the lack of clinical randomized studies, it has been unclear whether supplementation with vitamin D reduces the risk of cancer or cardiovascular disease. I also mentioned that we should soon have the results of a large randomized clinical trial, funded by the National Institute of Health (NIH), that is attempting to answer this question. The results of this study were recently published in the New England Journal of Medicine.

In this nationwide, randomized, placebo-controlled trial with 25,871 participants, the impact of vitamin D3 (cholecalciferol) at a dose of 2000 IU per day and marine n-3 (omega-3) fatty acids at a dose of 1 gram per day for the prevention of cancer and cardiovascular disease among men 50 years or older and women 55 years or older were evaluated. The investigators reported that supplementation with vitamin D did not result in a lower incidence of invasive cancer or cardiovascular events than placebo. Investigators also performed a pre-specified subgroup analysis of patients with serum 25(OH)D <20 ng/mL (50 nmol/L) and found similar results. There was also no difference between the vitamin D and placebo groups in the incidence of breast, prostate, or colorectal cancer.

In summary, based on the current scientific literature, we should take vitamin D if our baseline 25-hydroxyvitamin(25[OH]D) levels are below 10 ng/mL (25 nmol/L) to increase muscle strength (and therefore fall prevention). But as of now, there is no causal association between vitamin D levels above 10 ng/mL and a number of diseases such as cancer, infections, autoimmune diseases, and cardiovascular and metabolic diseases.

Of course, as always, you should consult with your healthcare provider to decide whether you need vitamin D supplementation or not. Some genetic predispositions may warrant your therapeutic vitamin D levels to be different than the above recommendation.