Woman at a Vegetable Stand

What? A Low-Fat Diet Prevents Breast Cancer?

Low-fat diets are back in the news this week. An impressive and important randomized, controlled clinical trial started way back in 1993 to test the possibility that a low-fat diet might reduce the risk of breast cancer in women after menopause. Needless to say, a lot has changed in 26 years since then. Back then, conventional wisdom held that low-fat diets were a panacea. Today, that thinking seems quite stale. “The low-fat diet failed,” says a recent issue of the Tufts Health & Nutrition Letter.

And yet, that seemingly outdated approach gave us evidence of important health benefits this week. Indeed, a diet rich in fruits, vegetables, and whole grains, but relatively low in fat, brought a lower risk of dying from breast cancer. In fact, this dietary pattern brought a 21 percent reduction in that risk. It’s a benefit that held up over 16 years follow-up.

An Important First

Here is where we note that these results are in a preliminary form. They’re scheduled for presentation at the annual meeting of the American Society for Clinical Oncology on June 2. Presumably, a full, peer-reviewed publication will follow. And that is a very necessary step.

Nonetheless, these results – if they hold up to scrutiny – could be quite important, as lead author Rowan Chlebowski explains:

This is significant, because this is the first intervention study targeting breast cancer where a reduction in deaths from breast cancer has been seen.

Is It the Fat?

But that brings us back to a question that bedevils us. Is it all about fats, carbs, and protein? Or is it something slightly more elusive – dietary quality? Stanford’s Christopher Gardner offers perspective:

Lentils and lollipops are both low-fat. Avocados and butter are both high fat.

When the women in this study were counseled to achieve a lower-fat diet by eating more fruits, veggies, and whole grains, they were doing more than lowering fat. They were increasing fiber and nutrients.

It’s also worth noting that the women in this intervention lost some weight, but not a lot. On average, it was about three percent of their body weight.

So if you look at the total picture of this study, it doesn’t really tell us that simply lowering fat in your diet will protect you from breast cancer. Rather, it may add to a growing consensus that diets full of fruits, vegetables, and whole grains can be beneficial. It offers support for the idea that dietary quality matters – perhaps more than dogma about macronutrients.

Click here for the study abstract and here for the press release from ASCO. Click here, here, and here for further reporting and perspective.

Woman at a Vegetable Stand, painting by Pieter Aertsen / WikiArt

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May 19, 2019