Does vitamin D help prevent cancer?
We have loads of evidence from population studies suggesting that it does.
We've reported on a number of studies linking vitamin D to risk for cancer, or survival rates.
And some clinical trials suggest that vitamin D helps people survive colorectal and breast cancer longer.
But no trial has clearly shown that higher vitamin D intakes or blood levels prevents any kind of cancer.
The discrepancy between population and clinical studies suggests that low vitamin D levels are a marker for ill health.
Low vitamin D is found in a wide range of disorders, and this makes sense because the inflammation associated with cancer, heart disease, and other major conditions lowers peoples' vitamin D levels.
This also fits with the fact that, in older people with low vitamin D levels, supplementation leads to slight gains in longevity.
Recent research shows two important things:
Now, research from University of California, San Diego School of Medicine indicates that breast cancer patients with high levels of vitamin D are twice as likely to survive the disease.
Higher vitamin D levels linked to longer breast cancer survival
The new research was conducted by renowned vitamin D expert Cedric F. Garland, DrPH, professor in the Department of Family and Preventive Medicine at USC San Diego (Mohr SB et al. 2014).
Previous research by Dr. Garland linked low vitamin D levels to a high risk of premenopausal breast cancer.
That finding prompted him to question the relationship between vitamin D levels and breast cancer survival rates.
As he explained, “Vitamin D metabolites switch on a protein that blocks aggressive cell division. As long as vitamin D receptors are present, tumor growth is prevented and [a tumor is] kept from expanding its blood supply. This is the reason for better survival in patients whose vitamin D blood levels are high.” (USC 2014)
Dr. Garland and his colleagues analyzed five studies in which the vitamin D levels of 4,443 breast cancer patients were tested at the time of diagnosis and an average of nine years later.
Women in the high-D-levels group had an average level of 30 nanograms per milliliter (ng/ml) in their blood.
The low-D-levels group averaged 17 ng/ml, and 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 [aid] to conventional breast cancer therapy,” said co-author Heather Hofflich, DO (USC 2014).
Garland urged the conduct of controlled clinical trials to confirm their findings, but suggested that physicians consider adding vitamin D supplements as part of a breast cancer patient's standard care.
As he said, “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 ng/ml has already been established.” (USC 2014)
How much vitamin D is needed?
A 2011 meta-analysis by Garland and colleagues linked a blood level of 50 ng/ml to a 50 percent lower risk of breast cancer.
While there are some variations in absorption, people can normally reach a blood level of 50 ng/ml by consuming 4,000 International Units (IU) per day from food and/or supplements.
Garland urged patients to ask their health care provider to measure their levels before substantially increasing vitamin D intake.
The current recommended daily allowance for vitamin D is 600 IU for adults and 800 IU for people over 70 years old.
Funding for the study was provided in part by U.S funding of the Penn State Cancer Institute of the Milton S. Hershey Medical Center.
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  • University of California, San Diego School of Medicine. (USC). Vitamin D Increases Breast Cancer Patient Survival. Accessed at