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Does High Dose Vitamin D Supplementation help with Prevention of Cancer?

Dec 13, 2019


A large scale nationwide clinical study showed that high dose Vitamin D supplementation did not lower the incidence (risk) of cancer and does not help with cancer prevention.

Vitamin D & Cancer Risk : VITamin D and omegA-3 trial (VITAL)

A prospective clinical study, by researchers at the Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, and funded by the National Institute of Health (NIH), was done to address the above question on whether Vitamin D supplementation helps in cancer prevention. The clinical trial VITAL (VITamin D and omegA-3 trial) (NCT01169259) was a nationwide, prospective, randomized trial, with the results recently published in the New England Journal of Medicine (Manson JE et al, New Engl J Med., 2019).

Vitamin D & Cancer Risk

Key highlights of the trial design, scientific rationale and results are shared below:

Trial Design for VITAL Study

  • There were a total of 25,871 participants in this study, that included men 50 years and older and women 55 years and older.
  • The participants were randomly divided into a group taking Vitamin D3 (cholecalciferol) supplement of 2000 IU per day, that is 2-3 times the recommended dietary allowance, and the placebo group with no Vitamin D supplementation.
  • Enrolled participants had no history of cancer at trial entry.
  • Primary endpoint was assessing diagnosis of invasive cancer of any type.
  • Median follow-up of the participants was 5.3 years.

Scientific Rationale for VITAL Study

  • Vitamin D supplementation is commonly recommended to prevent bone related disorders and is also considered to be beneficial for the prevention of cancer and cardiovascular disorders. However, the data from observational studies and meta-analysis showed a large variation in results.
  • The use of Vitamin D supplements in the US has increased substantially. (Kantor ED et al, JAMA, 2016)
  • Observational studies had shown an association of lower rates of cancer in places with more sun exposure, associated with more inherent Vitamin D synthesis by the body. (Mason JE et al, Contemp Clin Trials, 2012)
  • Also, observational studies showed an association between low serum levels of 25-hydroxy Vitamin D and increased risk of cancer. (Yin L et al, Prev. Med., 2013)
  • VITAL study was thus designed to test if a large dose of Vitamin D supplementation helps in cancer prevention in adults who had no prior history of cancer.

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VITamin D and omegA-3 trial Results

  • There was no statistically significant difference found in cancer diagnosis between the Vitamin D and placebo groups. Vitamin D supplementation was not associated with lower risk of cancer.
  • There was no significant difference observed with regards to incidence of breast, prostate or ovarian cancers.
  • Vitamin D supplementation did not lead to a significantly lower incidence of invasive cancer of any type when compared to the placebo group.
  • A minor observation was that participants with a normal body-mass-index (non-obese participants) who received Vitamin D supplement had a lower incidence of cancer when compared to placebo. This observation could be explained on the basis of hormonal dysregulation in obese individuals that could reduce the benefit of the Vitamin D supplement.

In summary, this large-scale, randomized study clearly shows that high dose Vitamin D supplementation does not result in lower incidence of cancer. Vitamin D supplementation may still help with bone related conditions and we do need sufficient amount of Vitamin D through sun exposure and diet for good health, but excessive supplementation does not add value from a cancer prevention perspective.

Cancer patients often have to deal with different chemotherapy side effects which affect their quality of life and look out for alternative therapies for cancer. Taking the right nutrition and supplements based on scientific considerations (avoiding guesswork and random selection) is the best natural remedy for cancer and treatment related side-effects.