You can chalk up another benefit for higher levels of vitamin D as a new study shows it’s associated with a decreased risk of breast cancer in postmenopausal women. That’s according to a new report from researchers at the University of California San Diego.
The same researchers who previously found favorable associations with vitamin D when it comes to avoiding lung and bladder cancers as well as multiple myeloma and adult leukemia.
Dr. Cedric Garland and a team of scientists looked at data from more than 5,000 women aged 55 and older to determine if elevated levels of vitamin D equated to fewer cases of breast cancer. The average age of the volunteers was 63 from two randomized clinical trials with 3,335 participants and a prospective study with another 1,713 women.
All participants were free of cancer at the outset and were tracked for a period of four years. During that time researchers monitored the vitamin D levels in the blood by measuring the serum 25-hydroxyvitamin D concentrations (25(OH)D). The National Academy of Medicine, a health advisory group to the government, recommends a minimum 20 nanograms per milliliter (ng/ml) level, but many now believe that number is too low.
During the study period a total of 77 cases of breast cancer were discovered and researchers said the risk of cancer appeared to decline with greater levels of vitamin D. "We found that participants with blood levels of 25(OH)D that were above 60 ng/ml had one-fifth the risk of breast cancer compared to those with less than 20 ng/ml," Garland said.
Multivariate regression was used to measure the link between 25(OH)D and breast cancer risk and the results were adjusted for age, body mass index, cigarette smoking and intake of calcium supplements. While some argue the studies do not necessarily prove cause and effect, researchers were convinced of the inverse correlation between vitamin D and breast cancer. "Increasing vitamin D blood levels substantially above 20 ng/ml appears to be important for the prevention of breast cancer," said study author Sharon McDonnel.
"This study was limited to postmenopausal breast cancer,” Garland said. “Further research is needed on whether high 25(OH)D levels might prevent premenopausal breast cancer, The population was also mainly white women so further research is needed on other ethnic groups. Nonetheless, this paper reports the strongest association yet between serum vitamin D and reduction in risk of breast cancer."