A new study has reported that vitamin D deficiency may increase the growth of bone metastases. Vitamin D has been shown to have anticancer effects in breast tissue. In addition, blood levels of vitamin D have been reported to be inversely correlated with risk of breast cancer. However, a possible causal relationship between vitamin D deficiency and breast cancer growth in bone has not been studied until now. The study examined the intraskeletal growth of human breast cancer cells in nude mice. Mice weaned onto a vitamin D-free diet developed vitamin D deficiency within four weeks, which was associated with secondary hyperparathyroidism and accelerated bone turnover. Osteolytic lesions appeared earlier and were significantly larger in vitamin D-deficient mice than in vitamin D-sufficient mice. The authors conclude that vitamin D deficiency promotes the growth of human breast cancer cells in the bones of nude mice.

Previous studies have reported benefits of adequate vitamin D

Vitamin D deficiency appears to be an important risk factor in breast cancer development and progression. Previous studies have found the following:

  • The majority of U.S. women are deficient in vitamin D. This is especially true of dark-skinned women who manufacture less vitamin D in response to sunlight exposure
  • Women with the highest levels of vitamin D intake have been found to have a reduced risk of developing breast cancer in numerous population studies. However, not all studies have found this association
  • Breast density was found to be inversely associated with vitamin D intake in one study of women with at least one first-degree or second-degree relative with breast or ovarian cancer. High breast density has been found to be associated with increased risk of breast cancer
  • Adequate calcium consumption appears to be required for the positive effects of vitamin D on bone to be fully realized
  • Vitamin D3 supplementation has been found to reduce disability from aromatase inhibitor-induced joint pain in some women
  • A phase II trial of daily vitamin D supplementation in women with bone metastases found that the vitamin D did not influence bone resorption or reduce pain overall. However, a reduction in the number of pain sites was observed and the treatment reduced elevated parathyroid hormone levels
  • A prospective study which used stored blood of breast cancer patients to measure Vitamin D levels found that women with deficient vitamin D levels had a significantly increased risk of distant recurrence and death compared with those with sufficient levels.

Please see our article on the importance of vitamin D for a more complete discussion.