BREAST cancer risk can be reduced by increasing vitamin D levels, suggests a study from the University of California San Diego, California, USA in collaboration with other institutions. In a cohort of postmenopausal women, it was found that those with blood levels of serum 25-hydroxyvitamin D (25[OH]D) above 60 ng/mL had a significantly lower risk of developing the disease than those whose level was below 20 ng/mL.
Vitamin D and Breast Cancer
The researchers chose 25(OH)D as a marker because it is the main form of vitamin D in the blood. Using data collected over a 15-year period from two randomised clinical trials and a prospective study that included a combined a total of 5,038 women, the team observed whether there was any association between vitamin D levels in the blood and the development of breast cancer. The women, who were cancer-free at enrolment, were all aged >55 years and had an average age of 63.
One-Fifth of the Risk
For this study, the team set 60 ng/mL as the minimum healthy blood level of 25(OH)D. To quantify the association between 25(OH)D levels and breast cancer, multivariate regression was used; the results were adjusted for age, BMI, cigarette smoking, and intake of calcium supplements. The analysis revealed that the participants with 25(OH)D blood levels >60 ng/mL had one-fifth of the risk of developing breast cancer compared to women whose levels were <20 ng/mL.
Preventing Breast Cancer
These findings have built upon previous epidemiological research linking higher vitamin D levels with a lower breast cancer risk, according to the researchers. “Increasing vitamin D levels substantially above 20 ng/mL appears to be important for the prevention of breast cancer,” commented first author Sharon McDonnel of GrassrootsHealth, a non-profit organisation involved in the study.
In total, there were 77 new breast cancer cases across the course of the combined studies; this was calculated to be an age-adjusted incidence rate of 512 cases per 100,000 person-years.
Further studies are now required to see whether high 25(OH)D can also help prevent breast cancer in premenopausal women. Additionally, as this study included mainly white women, further research on other ethnic groups is needed to validate the findings.
James Coker, Reporter
For the source and further information about the study, click here.