Vitamin D3 May Reduce Cancer Risk in Adults

In November 2020, Harvard researchers reported in JAMA Network Open that, “vitamin D3 may reduce the risk of developing advanced cancer among adults without a diagnosis of cancer at baseline; this protective effect is apparent for those, who have normal but not elevated body mass index.”

The research – Effect of Vitamin D3 Supplements on Development of Advanced Cancer – A Secondary Analysis of the VITAL Randomized Clinical Trial – included men aged 50 and older and women aged 55 and up, who were free of cancer and cardiovascular disease at the start of the study. 

The Harvard researchers cite prior research, which concluded that, “vitamin D may decrease tumor invasiveness and propensity to metastasize, leading to reduced cancer mortality. Higher serum 25-hydroxyvitamin D (25[OH]D) levels at diagnosis have been linked to longer survival in cancer patients.

The VITAL study examined the benefits and risks of vitamin D3 – cholecalciferol -at a dosage of 2000 international units (IU’s) per day, and marine omega-3 fatty acids – 1 gram daily – for primary prevention of cancer and cardiovascular disease, among the 25,871 study participants, who were recruited throughout the US and balanced by sex. An objective was to include at least 5000 Black participants.

To be included in the study group, participants had no history of cancer (except nonmelanoma skin cancer) or cardiovascular disease at study entry. Excluded from the study, were those individuals with kidney failure or dialysis, cirrhosis, history of hypercalcemia, or other serious conditions that would preclude participation. 

Additionally, all participants were required to limit vitamin D intake to no greater than 800 IU’s per day from all supplemental sources – including multivitamins, while forgoing the use of any out-of-study fish oil supplements. 

Those people, who met the study criteria, completed a 3-month placebo run-in phase. Randomized usage of vitamin D3, omega-3 fatty acids, both active agents, or both placebos, took place from November 2011 to March 2014 – with study medication ending on December 31, 2017 – yielding a median intervention period of 5.3 years. 

Prior to the start of the trial, blood samples – 25(OH)D – were collected during the run-in period for willing participants, which netted 16, 956 of the 25, 871 randomized participants.  

At 6 months, 1 year after randomization, then annually thereafter, participants received follow-up questionnaires to collect information on adherence to randomized treatments, use of non-study vitamin D and fish oil supplements, development of major illnesses, cancer recurrence, updates on risk factors, and potential side effects of the study agents. 

At conclusion, the researchers said, “in this more detailed secondary analysis of VITAL, vitamin D3 reduced the risk of developing advanced (metastatic or fatal) cancer among adults without a diagnosis of cancer at baseline. However, this protective effect was apparent only for those with normal BMI.”

We did not see differences in effect by race or baseline vitamin D levels” commented the researchers.

The Harvard researchers also said that, “additional randomized trials focusing on cancer patients should be considered, as well as, investigations of differential benefit by BMI.

Further, it was stated that, “even if vitamin D effects were modest, vitamin D supplementation at the studied levels are much less toxic and lower cost than many current cancer therapies.

The bottom line: get your body mass index – your weight relative to your height -under control. Then talk to your physician about getting a vitamin D blood test to determine the appropriate amount of an over-the-counter vitamin D3 supplement or the prescription form, if you have a deficient (less than 20 ng/dl) or insufficient level – especially if you have cancer in your family history or genetics.

Interested in reading more? Check out Research Confirms Optimum Vitamin D Blood Values