THURSDAY, Nov. 10, 2016 (HealthDay News) -- Vitamin D levels may affect breast cancer patients' chances of survival, a new study suggests.

Researchers analyzed data from nearly 1,700 breast cancer patients in California and found that higher vitamin D levels at diagnosis were associated with better overall survival. This link was strongest in premenopausal women.

Researchers found lower vitamin D levels in patients with advanced-stage tumors and the lowest levels in premenopausal women with triple-negative cancer. Triple-negative cancer is the most common type of breast cancer found in women with changes in a gene called BRCA1.

While the findings are consistent with previous studies, other factors may play a role and the study does not prove cause and effect, the researchers noted.

"Our findings provide compelling observational evidence for inverse associations between vitamin D levels and risk of breast cancer progression and death," Song Yao and colleagues concluded. Yao is an associate professor of oncology at the Roswell Park Cancer Institute in Buffalo, N.Y.

The study was published online Nov. 10 in the journal JAMA Oncology.

More information

The American Academy of Family Physicians has more on breast cancer.