Vitamin D Breast and Cancer Risk

Vitamin D Breast and Cancer Risk


Is there a relationship between vitamin D status and risk of breast cancer?


Vitamin D is essential for many processes in the body.  Bone health, immune function, reduction of inflammatory processes and variation of cell growth are among the many roles of vitamin D in the body. An excellent resource on vitamin D facts can be found online at the Office of Dietary Supplements.

Vitamin D status is assessed through a blood test called 25-hydroxy vitamin D. The shortened name is 25(OH)D. This is the blood test researchers use to determine vitamin D status for subjects in studies of the relationship between vitamin D and cancer.

Early studies suggest vitamin D deficiency might increase risk for breast cancer. Further research has been carried out in a number of countries involving thousands of subjects. The results of these studies have been mixed.

The majority conclude a significant role for vitamin D in breast cancer prevention could not be established for premenopausal breast cancer, though some studies have shown postmenopausal breast cancer risk to be reduced when vitamin D levels are at or above established normal ranges prior to cancer diagnosis. The table below gives a summary of results from two large, well-respected research projects on vitamin D and occurrence of breast cancer.

One is the EPIC study – the European Prospective Investigation of Cancer and Nutrition study. The other is a meta-analysis of nine studies that looked at vitamin D blood levels and cases of breast cancer. A meta-analysis is a way to combine results from several studies on the same topic. This approach allows for larger numbers of people to be studied together, and typically, more study subjects makes for a stronger study.

Vit D status and cancer incidence by subgroup: 

Vit D status and  cancer  incidence by  subgroup:

EPIC study

Meta-analysis of 9 studies


No relationship between  vitamin D blood levels and  breast cancer risk

No relationship between vitamin D blood levels and breast  cancer risk

Postmenopausal with hormone replacement therapy (HRT)

Higher vitamin D blood levels were linked with lower cancer risk

Postmenopausal women (both those using and not using  hormone therapy) had reduced risk of breast cancer if their  vitamin D blood levels were 27 ng/mL or more.  Risk was even lower for women with blood levels up to 35 ng/mL.  No additional benefit (reduction in risk) for women with vitamin D blood levels above 35 ng/mL.

Postmenopausal without hormone replacement therapy (HRT)


In summary, these studies suggest that for postmenopausal women in particular, it seems that having enough vitamin D to keep blood levels in a healthy range—a minimum blood level of 27 ng/mL (67 nmol/L)—is important for good health and cancer risk reduction. Your dietitian or doctor can help you determine how much vitamin D you may need to supplement to reach this goal.

Vitamin D Supplementation for Breast Cancer Survivors

There are some studies on vitamin D supplementation and breast cancer recurrence. These studies did not look directly at vitamin D levels in the blood, but instead had women report their use of vitamin D supplements. For breast cancer survivors, Vitamin D supplementation was associated with decreased risk of recurrence among estrogen receptor positive (ER+), but not estrogen receptor negative (ER-) tumors in the Harvard breast cancer pooling project.

Breast cancer patients receiving medications to lower estrogen levels especially need to have vitamin D levels monitored. These women also should ensure they get enough calcium and vitamin D to maintain bone density. And some research shows that breast cancer survivors may be at higher than average risk for vitamin D deficiency and insufficiency. Ask your medical team about checking your vitamin D levels, and supplementing if necessary.

Also, researchers have discovered that for some women who are experiencing joint pain and fatigue due to aromatase inhibitors—medications that lower estrogen levels—supplementing vitamin D can help lessen these unpleasant side effects.

Finally, keep in mind that some women are at higher risk of vitamin D deficiency due to other factors, such as a darker skin color, which blocks some of the sun's rays and limits the creation of vitamin D in the skin. Women who are older, or who live in northern areas also may need more vitamin D from diet or supplements to stay healthy.

To summarize, at this point, we don't know if taking vitamin D supplements will decrease breast cancer risk, or the risk of getting the disease again in women who've already had it. However, vitamin D is an essential nutrient. You need to take steps to ensure you get enough vitamin D for good health, especially bone health. Studies are ongoing and these should help us better understand the relationship between vitamin D nutrition and breast cancer prevention and recurrence.

The original question and answer were generously donated by Diana Dyer, MS, RD a cancer survivor, registered dietitian, organic garlic farmer, and the author of "A Dietitian's Cancer Story: Information & Inspiration for Recovery & Healing from a 3-time Cancer Survivor.

Question and Answer updated by JoAn Muncie, MS, RD, LD on behalf of the ON DPG


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Page updated: January 2014