Breast cancer patients with high levels of vitamin D in their blood are twice as likely to survive the disease as women with low levels of this nutrient, report University of California, San Diego School of Medicine researchers.
Background: In previous studies, Cedric F. Garland, DrPH, professor in the Department of Family and Preventive Medicine, showed that low vitamin D levels were linked to a high risk of premenopausal breast cancer. That finding prompted him to question the relationship between 25-hydroxyvitamin D — a metabolite produced by the body from the ingestion of vitamin D — and breast cancer survival rates.
The Evidence: Garland and colleagues performed a statistical analysis of five studies of 25-hydroxyvitamin D obtained at the time of patient diagnosis and their follow-up for an average of nine years. Combined, the studies included 4,443 breast cancer patients.
“Vitamin D metabolites increase communication between cells by switching on a protein that blocks aggressive cell division,” said Garland. “As long as vitamin D receptors are present tumor growth is prevented and kept from expanding its blood supply. Vitamin D receptors are not lost until a tumor is very advanced. This is the reason for better survival in patients whose vitamin D blood levels are high.”
Women in the high serum group had an average level of 30 nanograms per milliliter (ng/ml) of 25-hydroxyvitamin D in their blood. The low group averaged 17 ng/ml. The average level in patients with breast cancer in the United States is 17 ng/ml.
“The study has implications for including vitamin D as an adjuvant to conventional breast cancer therapy,” said co-author Heather Hofflich, DO, UC San Diego associate professor in the Department of Medicine.
Garland recommended randomized controlled clinical trials to confirm the findings but suggested physicians consider adding vitamin D into a breast cancer patient’s standard care now and then closely monitor the patient.
“There is no compelling reason to wait for further studies to incorporate vitamin D supplements into standard care regimens since a safe dose of vitamin D needed to achieve high serum levels above 30 nanograms per milliliter has already been established,” said Garland.
A 2011 meta-analysis by Garland and colleagues estimated that a serum level of 50 ng/ml is associated with 50 percent lower risk of breast cancer. While there are some variations in absorption, those who consume 4,000 International Units (IU) per day of vitamin D from food or a supplement normally would reach a serum level of 50 ng/ml. Garland urged patients to ask their health care provider to measure their levels before substantially increasing vitamin D intake.
According to the National Institutes of Health (USA), the current recommended daily allowance for vitamin D is 600 IU for adults and 800 IU for people over 70 years old.
My Take: While there is an association between low levels of vitamin D and a myriad of diseases, we still don’t know if taking vitamin D reduces the risk of breast cancer. And one can take too much. I think it is not unreasonable to check the vitamin D levels of patients with breast cancer, but do not have high-level evidence to say that I should do so. In a future blog, we’ll turn to foods that are rich in vitamin D. I’m Dr. Michael Hunter.
The small print: The material presented herein is informational only, and is not designed to provide specific guidance for an individual. Please check with a valued health care provider with any questions or concerns. As for me, I am a Harvard- , Yale- and UPenn-educated radiation oncologist, and I practice in the Seattle, WA (USA) area. I feel genuinely privileged to be able to share with you. If you enjoyed today’s offering, please consider clicking the follow button at the bottom of this page.
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1. University of California, San Diego Health Sciences. “Vitamin D increases breast cancer patient survival, study shows.” ScienceDaily. ScienceDaily, 6 March 2014. <www.sciencedaily.com/releases/2014/03/140306163236.htm>.
2. Sharif B. Mohr, Edward D. Gorham, June Kim, Heather Hofflich And Cedric F. Garland. Meta-analysis of Vitamin D Sufficiency for Improving Survival of Patients with Breast Cancer. Anticancer Research, March 2014