Can Vitamin D Lower Diabetes Risk and Reduce Cancer Progression, Mortality?

Vitamin D gel capsules
Vitamin D gel capsules
Vitamin D supplementation is associated with a 13% decrease in progression to diabetes in patients with prediabetes.

The following article is part of our coverage of the Endocrine Society’s annual meeting (ENDO 2021) that is being held virtually from March 20-23, 2021. Endocrinology Advisor‘s staff will report on the top research in hormone science and clinical care. Check back for the latest news from ENDO 2021.


New findings on the impact of vitamin D supplementation on type 2 diabetes risk,1 cancer mortality,2 and progression-free cancer survival3 were presented at the annual meeting of the Endocrine Society (ENDO 2021), held virtually from March 20 to 23, 2021.

Anastassios G. Pittas, MD, from Tufts Medical Center in Boston, Massachusetts, examined the results of 3 large trials to evaluate whether vitamin D supplementation can reduce the risk for progression to diabetes in people with prediabetes.1 The results of all 3 trials indicated that vitamin D supplementation decreased diabetes risk by approximately 13% among patients with prediabetes.

Dr Pittas also found that the protective effect of supplementation may be higher among individuals who have low baseline 25-hydroxyvitamin D levels (<12 ng/mL) and that risk reduction was proportional to serum levels of 25-hydroxyvitamin D achieved.

Another study was designed to evaluate whether daily supplementation with vitamin D3 (2000 IU) and marine omega-3 fatty acids (1 g) can be used in the primary prevention of cancer and cardiovascular disease.2 The study was based on results of the nationwide, randomized, placebo-controlled, 2×2 factorial VITamin D and OmegA-3 TriaL (VITAL; identifier NCT01169259). The findings were presented by JoAnn E. Manson, MD, DrPH, of Brigham and Women’s Hospital and Harvard Medical School in Boston, Massachusetts.

The total study cohort included 25,871 men and women (men aged ≥50 years, women aged ≥55 years; 5106 Black individuals) over a median treatment period of 5.3 years. Although vitamin D supplementation did not significantly reduce the total incidence of invasive cancer, it was associated with a reduction in total cancer mortality (Table). The association between supplementation and total cancer mortality was more pronounced when the analyses excluded years 1 and 2 years to account for latency.

This data was not as promising for the other coprimary endpoints of major cardiovascular events (HR, 0.97), other cardiovascular endpoints (no HR available), and all-cause mortality (HR, 0.99).

Table. Effect of Vitamin D3 and Omega-3 Fatty Acid Supplementation Cancer Outcomes2

OutcomeHazard RatioHazard Ratio,Excluding Year 1Hazard Ratio,Excluding Year 2
Total invasive cancer incidence0.96 (95% CI, 0.88-1.06)
Total cancer mortality0.83 (95% CI, 0.67-1.02)0.79 (95% CI, 0.63-0.99)0.75 (95% CI, 0.59-0.96)

“Additional research is needed to determine which individuals may be most likely to have a net benefit from vitamin D supplementation,” Dr Manson concluded.2

Kimmie Ng, MD, MPH, from the Dana-Farber Cancer Institute and Harvard Medical School in Boston, Massachusetts, presented a brief overview of the phase 2 SUNSHINE trial and phase 3 SOLARIS trial, both focused on vitamin D and progression of colorectal cancer.3

Dr Ng noted that there is “abundant preclinical data” in both colorectal cancer cell lines and animal models suggesting that vitamin D may have antineoplastic properties. Epidemiologic studies have also demonstrated this association, with data consistently showing a relationship between higher levels of plasma 25-hydroxyvitamin D and lower colorectal cancer risk as well as improved survival in patients with this disease.

Results of the randomized phase 2 SUNSHINE trial ( identifier NCT01516216) showed that adding high-dose vitamin D3 to standard chemotherapy regimens for metastatic colorectal cancer significantly improved progression-free survival. The confirmatory, phase 3 SOLARIS study ( identifier NCT04094688) is underway and will evaluate the efficacy of high-dose vs standard-dose vitamin D3 supplementation plus chemotherapy in metastatic colorectal cancer.

“Research efforts are also ongoing to elucidate the underlying mechanism of action of vitamin D in colorectal cancer,” Dr Ng concluded.3

Multiple authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Visit Endocrinology Advisor‘s conference section for more coverage from ENDO 2021.



1. Pittas AG. Vitamin D supplementation for prevention of type 2 diabetes. Poster presented at: ENDO 2021 virtual conference; March 20-23, 2021. Session S39.

2. Mason JE. The VITAL trial: updates on vitamin D. Poster presented at: ENDO 2021 virtual conference; March 20-23, 2021. Session S39.

3. Ng K. Vitamin D for prevention and treatment of colorectal cancer. Presented at: ENDO 2021 virtual conference; March 20-23, 2021. Session S39.