Vitamin D & Breast Cancer

What’s the connection?

Vitamin D & Breast Cancer

Strong evidence supports the connection between vitamin D deficiency and cancer development.

Vitamin D is becoming quite well known for its role in protecting against cancer. Indeed, this vitamin has been shown to stop abnormal cell growth and promote death in cancer cells. Converging lines of reasoning also indicate vitamin D may play an important role in treating and preventing breast cancer.

Reduced risk

Observational data suggests that higher levels of vitamin D are associated with decreased breast cancer risk and improved survival. A recent meta-analysis combining data from 30 prospective studies found that, compared to patients with the lowest levels of vitamin D, those with the highest levels had more than 40 percent reduced risk of death from breast cancer.

This corroborates a 2013 meta-analysis, which found that incremental increases in vitamin D levels were associated with a significant 3 percent decrease in breast cancer risk.

Another review paper by leading vitamin D researchers was recently published in the scientific journal Nature. The authors conclude that strong evidence supports the connection between vitamin D deficiency and cancer development. They also suggest that avoiding deficiency and supplementing with vitamin D is a safe, economical way to reduce cancer risk and improve cancer outcomes.

Lessened side effects

In addition to prevention and treatment, a third line of evidence suggests that vitamin D may reduce side effects of certain medications used to treat breast cancer. Aromatase inhibitors can cause joint pain known as arthralgia due to their estrogen-blocking activity. A randomized trial investigating this side effect found that supplementation with high dose vitamin D reduced aromatase inhibitor-induced joint pain.

In fact, vitamin D may function as a selective aromatase modulator; animal studies have shown that the activated form of this vitamin (also known as calcitriol) decreases aromatase expression in breast tissue, but actually increases it in bone marrow. Vitamin D decreased tissue levels of estrogen in the breast and decreased estrogen signalling. This suggests that while vitamin D has antiestrogenic effects in the breast, it appears to spare bone.

Upping our intake

We can bolster our vitamin D levels through moderate sun exposure, foods such as salmon, and supplements. Prior to undertaking high dose supplementation, women with breast cancer should seek evaluation for their vitamin D levels and consult their health care practitioner to determine if this therapy is appropriate. 

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