Tuesday, May 20, 2008

Does Vitamin D Help Prevent Breast Cancer?

Back in March I discussed an ad campaign sponsored by the Indoor Tanning Association promoting the supposed health benefits of tanning. Their message, in part, touted the benefits of Vitamin D, which is made in your body in a multi-step process that begins with exposure of your skin to ultraviolet light. I argued that with vitamin fortification of foods, vitamin D deficiency was rare in this country. One of my readers astutely pointed out that low vitamin D levels can cause problems even in patients who do not have an absolute deficiency.

A recent study from Mount Sinai Hospital in Toronto supports this idea. The researchers measured vitamin D levels in the blood of 512 women at the time of their breast cancer diagnosis (between 1989 and 1995). In 2006, distant disease-free survival (the percentage of women alive with no evidence of spread of their disease) was 83% for the women with adequate vitamin D levels, compared with 79% for those with insufficient levels and 69% for those who were deficient.

Considering the large number of women diagnosed with breast cancer each year, these differences are huge.

What does this mean? It means a healthy level of vitamin D is probably important for a lot more than just maintaining strong bones.

It is important to note, though, that this study does NOT show that vitamin D helps treat breast cancer, so if you already have breast cancer, supplementation may not help. Also, the study showed that the women with the very highest vitamin D levels seemed to have worse survival, so mega-doses of vitamin D may not be such a good idea, either.

So how much is enough? That varies with age, gender, and whether you are pregnant or nursing a baby. As a general rule of thumb, between 400-600 international units (IU) appears to be a healthy amount. For your specific case, you can consult the Vitamin D Fact Sheet from the Office of Dietary Supplements of the National Institutes of Health here.

Where do you get vitamin D? Your body will make it as long as you get some sun – experts recommend 15 minutes or so a few times a week (without sunscreen, so longer if you have sunscreen on) – but this will depend on where you live (the sun is stronger the closer you are to the equator). Some foods naturally contain vitamin D, like fish (especially salmon, tuna, and mackerel), beef liver, and egg yolks. The major source of dietary vitamin D in the US is fortified dairy foods.

This study was released in advance of the 2008 annual meeting of the American Society of Clinical Oncology (ASCO), which will be held at the end of the month in Chicago. The study has gotten a lot of media attention so far and as I will be at ASCO I will share what I learn.

Check out the study abstract here.

Related posts:
Breast Cancer Risk & Alcohol: Isn’t Red Wine Good for You?
Cancer Stem Cells and Familiar Risk of Breast Cancer
An Advertisement That Supports Skin Cancer


outre said...

The whole vitamin D thing concerns me because...
too many people will think

Vitamin D = Natural
Natural = Good
Good = I should get lots of it!

When I mention that no one really knows the full extent of the role Vitamin D plays in cancer, that it may actually be involved in promoting cell growth, it tends to fall on deaf ears. I have a feeling if I wasn't working where I work, people would believe me more readily.

Heather said...

I recently read an article about how the lack of vitamin D in the winter is why so many people suffer from colds then, whereas in the summer you obviously get more sun - therefore fewer/no colds. I worry about skin cancer though and avoid dairy products. I am thinking of taking a supplement. Thanks for the interesting post!

Anonymous said...

I think heather is right about taking supplements. The vitamin d fact sheet mentioned that ultraviolet rays can also cause skin cancer.

Ryan W. said...

I found a blog post that makes an interesting argument that some of the studies showing lower Vit. D linked to increased mortality in osteoporosis and autoimmune disease are showing an effect of infection and Vit. D receptor disregulation rather than simple deficiency.

You won't find any actual research that shows vitamin D + calcium increases bone density above calcium alone, though some people
still assert that conclusion. Vitamin D raises blood levels of calcium, yes. But not bone density.

Many people with low 25D have high 1,25D which is a product of 25D
That argues against deficiency in some cases. And in favor of infection + occasionally dysregulation of the Vitamin D Receptor resulting in overproduction of
1,25D from 25D (which leads to low levels of 25D, which appears like deficiency)


They say high levels of 25D deactivates the Vitamin D receptor based on molecular modeling, though. That part I question. How much D3 supplementation does it take to maximize cathelidicin production?
I cannot find an answer to that question, and it should be simple.

JKL said...

Until recently, I never worried about my vitamin consumption. When I heard of what could happen I immediately started taking vitamins.

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Sadly this is only a myth there's no doubt about it.