Vitamin D and Breast Cancer: Are they married or just acquaintances?

With recent headlines like Vitamin D Enhances Breast Cancer Survival, a woman could hardly be faulted for running out and stacking up on Vitamin D pills.  The meta-analysis study (a compilation of studies) upon which this headline and similar ones are based, was published in Anticancer Research and showed that the higher the Vitamin D level at the time of diagnosis, the better the prognosis. On the surface, this would suggest a cause and effect relationship.  To the untrained eye, one might conclude that raising Vitamin D levels has some type of anti-cancer effect.

However, the evidence to date would suggest that this is not the case. First, even in this study, even women with very high levels of Vitamin D were still diagnosed with breast cancer.  The higher levels of vitamin D simply meant average longer survival. So what do I think is going on?

I believe, and a recent study, which I will discuss in a moment, supports my tentative conclusion, that this is a matter of correlation between vitamin D levels and one's state of health..  As correlation does not imply causation, raising vitamin D levels artificially high with Vitamin D supplements will neither prevent cancer, as the first study clearly showed, nor improve its prognosis. Why?

In a study published in the Lancet, the British medical journal, titled,  The effect of Vitamin D supplementation on skeletal, vascular, or cancer outcomes: a trial sequential meta analysis, the researchers compiled a representative group of Vitamin D studies and divided them into two groups. The first group included studies such as the breast cancer study above that showed consistently that higher levels of vitamin D correlated well with better health and disease outcomes. The second group of studies were double.blind randomized controlled studies that showed that Vitamin D supplementation versus placebo had little effect on overall health.

The authors of this study proffered what they believe to be the plausible explanation for the inconsistencies between the two groups of studies.  They tentatively concluded that raising Vitamin D levels above a certain threshold of adequacy doesn't prevent disease; rather, disease lowers Vitamin D levels.  as applied to the breast cancer study, this means that the women with the highest level of Vitamin D at the time of breast cancer diagnosis were healthier than those with lower Vitamin D levels and therefore had a better prognosis.  The worse the breast cancer, the unhealthier the patient, the lower the Vitamin D level, the poorer the prognosis.

As with all studies, one can reach no conclusive decisions from either of these studies. They merely add to our knowledge. My take-away from these studies is that Vitamin D is essential to human health and having levels above 20 mcg is essential and some say above 30 mcg. is ideal. 

The best way to get your Vitamin D remains 15 minutes of daily sun exposure to your torso/extremities. Alternatively, consuming food products with high concentration of Vitamin D like unsweetened Almond Milk and wild Alaskan Salmon are second, with Vitamin D pills coming in third. If you are taking pills because you absolutely can't do the first two then the recommended daily allowance (RDA) if you are below age 70 is 600 iu. and above age 70 it's 800 iu. That's not a typo. By the way, RDAs were developed to cover 97% of the population's needs. 

Supplementing with levels above these numbers has not been shown to have any benefit so save your money.  Again, this is what the current preponderance of evidence shows.  I'll let you know if something changes. Some large population studies are underway with expected publication in 2016 and 2017 so stay tuned.