A shrewdly designed study adds support to the idea that vitamin D may play a role in breast and colon cancer risk reduction. The study has significant caveats worth noting, but it's being widely reported in the media without those caveats.
Let's throw some bright light on it and determine what might be in it for you.
New evidence demonstrates the link between higher vitamin D levels, derived largely from exposure to sunlight, and lower risk of breast and colon cancers.
This study in 50 words or less
Scientists compared existing data on blood levels of a vitamin D by-product with sunlight/cloud cover maps and then to geographic breast and colon cancer rates. They used data gathered in winter, when sun exposure is lowest. They found a consistent link between low sun exposure/blood levels of D and higher cancer rates.
Yes, but. . .
There are good reasons to proceed with caution, since there are questions about the scientists' independence. I'm writing about the study because it's being widely reported and needs some truth-squadding.
Significant caveat I: As of this writing, the study has not been published. Only summaries of it are available. When published in the August issue of Nutrition Reports, the study will be available here. I'll come back and update this entry if necessary.
Significant caveat II: The study was led and backed by researchers affiliated with the Sunlight, Nutrition and Health Research Center, San Francisco. This group is devoted to publicizing the role of vitamin D in public health, and receives some funding from industry groups that include the Indoor Tanning Association.
Significant caveat III: The authors offer the report as evidence that many lives can be saved worldwide (they offer 600,000 as a number) by increasing vitamin D intake--a conclusion that adds unnecessary rhetorical flourish to the group's core message, and may muddy the view of the science underneath.
The study does not prove cause and effect, only an association between sun light, vitamin D blood levels, and the cancers.
While others studies have linked vitamin D levels to geographic latitude and disease risk, this is the first to include measured sunlight and cloud cover to the calculations, adding weight to the argument that sunlight exposure is a key factor in breast and colon cancer incidence.
So what are you going to do about it?
This may be an opportunity, if you'd like, to consider the role of vitamin D in your wellness plan, and (only in consultation with your oncologist or physician!) in your cancer treatment or risk reduction efforts.
It's difficult, but worth the effort, to get much vitamin D from your diet: Primary food sources include: D-enriched milk, some dairy products and cereals; and oily fish such as salmon, tuna and sardines.