Vitamin D as a prevention against breast cancer
Dr Song Yao - Roswell Cancer Center Institute, New York, USA
Can you tell us more about your work on vitamin D as a preventative measure for breast cancer?
Vitamin D is one of the micronutrients we normally get from sun exposure and a little bit from our diet. There have been a lot of animal studies and cell culture studies showing that vitamin D is beneficial to prevent and to cure cancer cells. So we’re interested in looking at vitamin D to prevent breast cancer in breast cancer patients. So this is a human-based study and what we have found in a previous study is that vitamin D levels as measured in the blood is associated with a lower risk of breast cancer, particularly of the more aggressive subtypes we call triple negative breast cancer, in premenopausal women but not so much in post-menopausal women. So in this study we were trying to replicate our previous findings and also were interested in further investigations to look whether vitamin D levels are also associated with a breast cancer patient’s outcome, specifically cancer recurrence and survival. So that’s why we are doing the study.
And you’ve studied with regards to post-menopausal women?
In the previous study we stratified the analysis, basically to separate the analysis in premenopausal women and post-menopausal women. The associations are mostly in the premenopausal women but not much in the post-menopausal women. So we were thinking that maybe vitamin D works better for younger women. Also that makes sense from our own data because younger women tend to have more aggressive breast cancer and also vitamin D, we showed that vitamin D has a stronger effect against more aggressive breast cancer.
Should women be worried if they have low doses of vitamin D?
There is a lot of debate on the optimal level of vitamin D in humans. Our study is doing an early phase so we cannot give this great recommendation of the cut-off levels. But I think it would be helpful to maintain the level as recommended by the Institute of Medicine.
What about clinical trials?
Yes, there is one large trial led by a group from Harvard; the trial is called VITAL so it’s a randomised prevention trial testing vitamin D and omega-3 in prevention of cardiovascular disease and cancers. So that trial is still ongoing, I think it will take several years until we can see some results from that. But before that currently the studies, including ours, are considered as preliminary and the trial will provide a definitive answer.
Is much understood about the mechanism between vitamin D and breast cancer prevention?
Yes, as I mentioned before, there have been a lot of experimental studies done in animals and cultured cells in which they show vitamin D is capable of causing cancer cell death, to inhibit cell growth. So I think there are a lot more mechanistic studies done but those studies provide great clues for our study but finally we still need to rely on population-based studies and including the trials to give us the definitive answer of whether vitamin D works in humans or not.