Vitamin D is an important nutrient for the immune system, muscle health, and cell growth. The vitamin may also slow the progression of prostate cancer.

Some studies suggest that adequate vitamin D levels could reduce the risk or severity of prostate cancer. However, the evidence is still inconclusive.

The potential for vitamin D to disrupt cancer growth is well-documented, but the role of vitamin D supplementation in treating prostate cancer remains controversial.

Some studies suggest that high doses of vitamin D might improve treatment outcomes for prostate cancer, while others find no such correlation. Vitamin D should not replace standard treatments for prostate cancer.

Keep reading to learn more about the relationship between vitamin D and prostate cancer.

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The body breaks vitamin D down into the compound calcitriol. Several studies suggest that calcitriol may slow the growth of cancers, including prostate cancer. However, many of these studies examine cancer cells in a laboratory or in animals rather than the human body.

Vitamin D also plays an important role in immune function. Vitamin D deficiency may increase inflammation, which is a risk factor for many diseases, including cancer.

Research on the specific benefits of vitamin D for treating or preventing prostate cancer has produced mixed results.

Research findings

A 2017 study found lower vitamin D levels in people with prostate cancer. The study also found that prostate cancer was more severe in people with the lowest vitamin D levels and found a correlation between low vitamin D and higher levels of inflammation in people with prostate cancer.

This points to a potential role of vitamin D in preventing or slowing cancer growth but does not show that supplementation improves prostate cancer outcomes. However, some earlier studies cited in the analysis did find that vitamin D supplementation correlated with lower prostate-specific antigen (PSA) levels. PSA is a protein produced by prostate cells, and elevated levels can indicate the possible presence of prostate cancer.

A 2018 review of seven studies found an association between vitamin D levels and prostate cancer prognosis. Higher blood vitamin D levels were associated with a reduced risk of death in people with prostate cancer.

Some of the studies in this review included people supplementing with vitamin D, which raised blood vitamin D levels. This suggests that taking vitamin D may help reduce the risk of prostate cancer death, but more work is necessary to confirm this.

A 2019 review of 22 studies found an association between vitamin D levels and PSA levels in response to treatment. However, the review did not find differences in other outcomes, such as death or cancer growth.

This review points to prior studies that suggest vitamin D from the sun might reduce prostate cancer risk. It also highlights previous research that found an increased risk of prostate cancer in people with high vitamin D levels in their blood.

These contrasting findings prevent any firm conclusions from being drawn on the benefits of vitamin D for people with prostate cancer. More research is needed to compare people who do and do not take vitamin D while controlling for other factors that might affect prostate cancer.

There is evidence that vitamin D can help people with prostate cancer undergoing hormone therapy, which can reduce bone mineral density. Vitamin D and calcium together work to reduce the risk of osteoporosis and bone fractures.

Natural sunlight is a highly accessible source of vitamin D for many people. Between 5–30 minutes of sun exposure during the brightest hours may offer sufficient vitamin D. However, too much sun exposure can increase the risk of skin cancer.

Some other sources of vitamin D include:

A dietary supplement can also elevate vitamin D levels. The recommended daily intake of vitamin D for males aged 50—70 is 15 micrograms (mcg), or 600 international units (IU). The recommended intake for males over 70 is 20 mcg or 800 IU.

Low-grade prostate cancers typically grow very slowly. In some people, prostate cancer might require no treatment. Instead, people may undergo “active surveillance.” Protocols for active surveillance vary, but all involve regular PSA blood tests, usually every 6 months, and interval biopsies, usually every 1–2 years, as well as a possible role for prostate MRI.

People with low-grade cancers may consider using alternative and complementary remedies, such as vitamin D. A 2013 study suggests that vitamin D3 supplementation may benefit patients with early stage, low-risk prostate cancer on active surveillance.

People who require treatment should not use vitamin D as a substitute for other treatments. Standard treatment options include:

People undergoing hormonal therapy need vitamin D supplements to prevent bone density loss.

Prostate cancer is a complex disease. It is often slow-growing and unlikely to cause serious harm to some people. However, it may be aggressive and potentially fatal to others. People who choose not to treat low-grade cancers may consider alternative and complementary remedies, such as vitamin D.

However, this is not standard of care, and research has not definitively shown that vitamin D can slow or reverse prostate cancer progression. There is no evidence that vitamin D is a substitute for standard cancer treatments.

Vitamin D may help reduce the risk of other health issues, such as bone mineral density loss. People interested in adding vitamin D to their treatment regimen should discuss doing so with a doctor.