On 15th November my blog was dedicated to a very poorly interpreted piece of research which purported to show a link between red meat eating and an increased risk of breast cancer [click here]. Even the most cursory look at this study revealed a piece of research hardly worth the paper it was written on. As coincidence would have it, that very same day saw the publication of another study which supports the notion that eating fat-rich foods like red meat does not boost the risk of breast cancer.

The study in question was published in the American Journal of Epidemiology. In it, American researchers assessed the relationship between fat intake and breast cancer in more than 80,000 women over a 20-year period.

Here’s a summary of their findings:

• total fat intake was NOT associated with risk of breast cancer

• saturated fat intake was NOT associated with risk of breast cancer

• for women with a condition known as insulin resistance (which can lead to type 2 diabetes in time), HIGHER FAT INTAKE was associated with a REDCUCED risk of breast cancer

The lead author of this study, Dr Esther Kim, commented: “The take-home message for post-menopausal women in that limiting dietary fat in unlikely to reduce their risk for breast cancer.”

What is particularly interesting about this study is the relationship it found in some women between higher dietary fat intake and reduced risk of breast cancer. While it is not known for sure what might be responsible for this association, individuals eating relatively large amounts of fat will tend to eat less carbohydrate in the form of sugar and/or starch.

The relevance of this is that eating a carb-rich diet can cause elevated levels of insulin and changes in the levels of a substance known as insulin-like growth factor which have been linked with an increased risk of cancer. This issue was discussed in more depth in my blog post which reported a study which found higher levels of white bread intake associated with an increased risk of kidney cancer [click here].

What I personally find curious about this recent study is how little publicity it got. In fact, I only found this study because I happened to notice it while looking at another study in the same edition of the American Journal of Epidemiology. Compare that to the general hullabaloo that followed the poor piece of science published at about the same time which was said to find a link between red meat and breast cancer.

This disparity in publicity has an important bearing not just on what the general public believe, but the medical profession too. High profile studies with a lot of attendant publicity tend to embed themselves in the minds of doctors. And such studies are also the ones that will tend to be referred to in subsequent research and reviews. This phenomenon – referred to as ‘quotation bias’ in the scientific community - only serves to reinforce a concept or belief that may not reflect the balance of evidence at all.

I believe there’s quite a few nutritional notions have become dietary dogma not because of good science, but because of poor science compounded by quotation bias. Whenever possible, I’ll use this site to attempt to separate fact from fiction.

References:

1. Kim EHJ, et al. Dietary fat and risk of postmenopausal breast cancer in a 20-year follow-up. American Journal of Epidemiology. 2006;164:990-997

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