Vitamin D, essential for calcium absorption and normal functioning of the immune system, has also been shown to improve breast cancer survival rates, according to researchers at the University of California, San Diego, School of Medicine. Their findings were published in the March issue of the journal .
Previous work by Dr. Cedric F. Garland, an adjunct professor of family and preventive medicine, demonstrated that low vitamin D levels were linked to a higher risk of breast cancer in premenopausal women.
He said that this finding led him to investigate the relationship between 25-hydroxyvitamin D—a metabolite the body produces by ingesting vitamin D—and breast cancer survival rates.
"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 serum group" averaged 17 ng/ml. The average level in patients with breast cancer in the U.S. is 17 ng/ml, according to the report.
Garland urged patients to ask their healthcare providers to measure their levels of vitamin D before increasing intake.
For most adults, the recommended daily allowance of vitamin D is 600 international units (IU), according to the National Institutes of Health. For people over 70 years old, it is 800 IU.