In fact, recent research has found that vitamin D, which your body produces through sun exposure can help prevent and treat colorectal, breast, and prostate cancer. This is significant because these cancers count for 35% of cancer cases and 20% of cancer deaths in the United States (1). (Updated Mar 13, 2021)

Dr. Cedric F. Garland of the University of California’s San Diego Moores Cancer Center is the epidemiologist who has connected the dots between Vitamin D deficiency and cancer (2).

Studies show that the vitamin fights cancer, by promoting cellular differentiation, preventing cancer cell growth, inducing apoptosis and preventing blood vessel formation within tumors (3).

The review, published in the Journal of Cancer, found that 4000 IU/d of vitamin D3 could inhibit cancer progression, as measured by the main biomarker 25-hydroxycholecalciferol [25(OH)D] (4).

Breast Cancer

Breast cancer studies found that adequate to high vitamin D serum levels could lower cancer mortality by 44% (5).

In fact, women with very low levels of vitamin D at diagnosis were 94% more likely to develop metastases than women with normal levels, and were 73% more likely to die.

“Doctors should emphasize the importance of maintaining adequate serum vitamin D levels, which would be 40 to 60 ng/mL for cancer prevention, and encourage their patients to have their vitamin D status regularly checked, especially in winter, to ensure that adequate serum levels are being maintained,” said first author Sharif B. Mohr, MD, from the Naval Health Research Center in San Diego (6).

For women already diagnosed with breast cancer, vitamin D levels could go as high as 80 ng/mL, he told Medscape Medical News.

Low levels of vitamin D were not only found to increase risk of developing breast cancer but is also linked to more-aggressive tumors and worse outcomes (7).

“Although much more research needs to be done, research from our lab and others suggests that people at risk for breast cancer should know their vitamin D levels and take steps to correct any deficiencies,” said Brian Feldman, MD, PhD, assistant professor of pediatrics.

Prostate Cancer

A new study from the Northwestern University Feinberg School of Medicine suggests a link between low levels of the vitamin and aggressive prostate cancer. In fact, low serum vitamin D was found to be a clear markers of prostate cancer risk (8).

The vitamin also prevented the proliferation and differentiation of cancer cells.

The cross-sectional study of research from 2009-2014 was a part of a  larger epidemiologic study of 1760 cancer screenings compared to healthy controls.

“If you place prostate cancer cells in a dish with vitamin D, growth rate slows, the cells become less invasive, and there is a greater likelihood the cells undergo apoptosis,” says Adam Murphy, MD, lead author and assistant professor of Urology, Northwestern University.

“Based on our previous research, we have strong evidence that people who have no prostate cancer have higher levels of vitamin D than those patients who had a diagnosis of prostate cancer.”

The vitamin also improved bone health, rheumatoid arthritis, and other types of cancer.

It was found that supplementation with vitamin D3 could prevent the spread of disease (9)