Studies of the benefits of vitamin D have been controversial, with some showing significant benefits and other showing none, and most not differentiating between hormone receptor types. The difference often is in the study design. Research on serum vitamin D—the form that circulates in the blood—often find more cancer-fighting evidence. Those that study vitamin D intake are less convincing. This could be because our bodies use vitamin D differently, depending on a variety of factors: age, diet, activity level, and even genetics. Also, serum vitamin D might come from the most natural of all sources—the sun or our diets—whereas vitamin D intake often measures artificial forms. Still, even researchers who study the serum form advocate supplements, especially for people in northern latitudes who do not have the benefit of regular sunny days.
Triple Negative and Vitamin D
A case study of 91 breast cancer patients in Whittier, California found that those with triple-negative were more likely to be deficient in serum vitamin D—doctors measured a form called 25 (OH)D. Fifteen of the patients were triple-negative, and the majority of those—87 percent—had lower levels of the vitamin than other cancer patients, with the remaining 13 percent being borderline low. This ties in with other research on triple negative and on vitamin D, the researchers write: “African American women have the highest breast cancer specific mortality rates, the lowest serum levels of 25(OH)D, and the highest incidence of aggressive triple-negative or basal-like tumors.”
A specific form of active vitamin D3 known as Gemini 0097 substantially reduced the development of both ER- and ER+ breast cancer in rats, according to research done at Rutgers University. Scientists injected rats with breast cancers then treated them with Gemini 0097. The vitamin D slowed the growth of ER-positive by 60 percent and ER-negative by 50 percent. As with all studies in animals, more research needs to be done to determine the effects of Gemini 0097 on human cancers. One benefit so far is that Gemini 0097 is less toxic than other forms of synthetic vitamin D and does not lead to an overload of calcium, the vitamin’s most common side-effect.
Research Reviews on Vitamin D and Breast Cancer
Several research reviews support the benefits of vitamin D. According to a 2009 review done by scientists at the University of California, San Diego, low levels of serum Vitamin D are connected to a variety of cancers, including breast, colon, ovarian, renal, pancreatic, and aggressive forms of prostate, and other cancers. Researchers projected that raising our intake of vitamin D would prevent 58,000 new cases of breast cancer each year; 2,000 mg a day, they say, can increase serum levels to a healthier range without other risks.
In a 2006 review, scientists cited numerous studies that link both calcium and vitamin D to breast cancer risk for premenopausal and well as postmenopausal women. And in a third review, in 2007, researchers noted that 2000 IU a day of Vitamin D3 can reduce the risk of breast cancer by 50 percent.
Research on 16,818 participants in the Third National Health and Nutrition Examination Survey (NHANES III) determined that women with higher levels of serum vitamin D (over 25 ng/mL) had only about one fourth the mortality rate from breast cancer as those with lower amounts. Survey participants were 17 years or older at enrollment and were followed from 1988–1994 through 2000.
Research on Vitamin D Supplements and Breast Cancer
Yet a long-term study—seven years—of postmenopausal women as part of the Women’s Health Initiative found no relationship between Vitamin D and breast cancer. Researchers gave women 1000 mg of elemental calcium with 400 IU of vitamin D3 daily. Those women had no lower risk of breast cancer than those receiving a placebo.
And research using data from the Cancer Prevention Study-II Nutrition Study also found no association between postmenopausal breast cancer risk and levels of Vitamin D, regardless of hormone receptor status, body mass index, postmenopausal hormone therapy, weight gain, season of the year, or calcium intake. However, researchers did note that:
• the source of Vitamin D might be important, with women who get the vitamin through their diet—in fortified milk or fish, for example—having higher levels circulating in their bodies. Also, dietary Vitamin D is strongly correlated with calcium, which may be effective in fighting breast cancer.
• Women living at northern latitudes—above 37° —get less Vitamin D from the sun and were more likely to have breast cancer than those in southern latitudes.