A new study confirms that healthy blood levels of vitamin D are important in women diagnosed with breast cancer and it also reveals new findings regarding the benefits of vitamin D for this condition.
In this study, featured in the May 2012 issue of Carcinogenesis, a group of scientists out of Catholic University Leuven in Belgium evaluated the relation between vitamin D status and breast cancer. They wanted to know if vitamin D status at the time of diagnosis correlates or influences tumor characteristics, survival, and cancer relapse. Furthermore, they wanted to know if any of this was influenced by vitamin D related genes.
The researchers performed blood tests on 1800 early stage breast cancer patients at the time they received the diagnosis (before starting any treatment). They evaluated the blood levels of vitamin D (25OHD levels) and looked at the specific genes related to vitamin D pathway.
25OHD levels of >30 ng/mL were classified as “high” and were observed in 35.9% of the participants. 31.7% of women had “intermediate” 25OHD levels- between 20-30 ng/mL and 32.4% of the women had “low” 25OHD levels, classified as <20 ng/mL.
They made the following observations:
1. Low levels of 25OHD serum were significantly associated with larger tumors (at the time of the diagnosis) and high levels of 25OHD levels were associated with smaller breast tumors. This is the most remarkable finding, because previous studies did not show the link between vitamin D levels and tumor size.
2. High blood levels of vitamin D at the time of diagnosis were significantly associated with a better overall survival and disease-specific survival. Basically this means that women with low serum 25OHD levels at breast cancer diagnosis have an increased risk of death from any (breast cancer related or unrelated) cause. There was noted some improvement in the disease-free interval as well.
3. It is already known that the incidence of breast cancer is higher in postmenopausal women (60 % of women diagnosed with breast cancer are menopausal). Vitamin D deficiency is also more common after menopause.
This study found that high levels of vitamin D significantly improved the disease outcome among postmenopausal women (compared with those women who had low levels of 25OHD).
4. Researchers also found that that vitamin D related genes significantly influence the serum levels of 25OHD, but did not correlate with tumor size or survival.
This fits with past research nicely. Past studies have found:
- An increased risk of developing breast cancer with higher latitude, low sun exposure and low vitamin D status.
- A meta-analysis indicated a slight decrease in breast cancer risk following preventive vitamin D intake.
- A large randomized, placebo-controlled study from Women’s Health Initiative (WHI) showed that supplementation with vitamin D and calcium reduced the risk of breast and colorectal cancers.
In conclusion, this study suggests that vitamin D supplementation and sun exposure prior to breast cancer diagnosis helps with survival and reducing the size of breast tumors. Here, levels above 30 ng/mL were better than lower levels.