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, scientists have found. In previous studies, Cedric F Garland, professor in the Department of Family and Preventive Medicine at the University of California - San Diego, showed that low vitamin D levels were linked to a high risk of premenopausal breast cancer. The average level in patients with breast cancer in the US 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, UC San Diego associate professor in the Department of Medicine. Garland recommended randomised 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. The study is published in the journal Anticancer.
The findings, he said, 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.
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 tumour growth is prevented and kept from expanding its blood supply.
Vitamin D receptors are not lost until a tumour is very advanced. This is the reason for better survival in patients whose vitamin D blood levels are high," Garland said. Women in the high serum group had an average level of 30 nanograms per millilitre (ng/ml) of 25-hydroxyvitamin D in their blood. The low group averaged 17 ng/ml.