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Red Meat and Breast Cancer

An otherwise excellent story about breast cancer is limited by not citing hard numbers

A certain type of breast cancer is linked to eating a lot of red meat, according to The Washington Post and several other news reporting agencies. As MSNBC put it, “Women who ate more than 1½ servings of red meat per day were almost twice as likely to develop hormone-related breast cancer as those who ate fewer than three portions per week.” This discovery was found by a team at Harvard Medical School based on data from the Nurses' Health Study II, involving over 90,000 women.

But while the Washington Post article cites the number of breast cancers discovered each year in the U.S. (over 200,000), and the number of deaths attributed to breast cancer each year (over 40,000), it says virtually nothing about the specific kind of hormone-related breast cancer that has now been linked to consumption of red meat. If this type of breast cancer is extremely prevalent, a two-fold increase would be extremely serious, while if the cancer is rather rare, such an increase may not make much difference.

The study was published in the Archives of Internal Medicine, and the abstract points out that 512 of the 1021 women diagnosed with invasive breast carcinoma had the specific type of breast cancer that is associated with red meat consumption, or about one half. If a full half of all occurring breast cancers are “estrogen and progesterone receptor positive,” then this result affects many women. After all, about one in eight women in the United States will get breast cancer. Does that mean that if we reduce our red meat intake to fewer than three servings per week, we can halve our risk? Would the risk then only be one in 16?

Not quite. First of all, this study only looked at premenopausal breast cancer cases. But most new diagnoses of breast cancer are in postmenopausal women. Women over the age 50 constitute about 75% of new cases. While the onset of menopause may be later than age 50, the Harvard Medical study does not apply to the entire population of women. It specifically looks at women ages 38-58 who have not yet undergone menopause.

The results relating meat consumption to the hormonally-related breast cancer rates may not hold true for postmenopausal women, who constitute a majority of breast cancer patients. Unfortunately, these news reports did not bother to find the incidence rate of breast cancers before menopause, nor the percentage of those that are due to the specific type of breast cancer affected by red meat. If about 30% of breast cancers occur in premenopausal women, and about half of these are hormonally related, then only about 15% of the all breast cancers are potentially affected by this study’s results. This amounts to just under two percent of the whole population.

Furthermore, as a consumer, keep in mind that even if there is a causal relationship, as suggested by the study – in other words, that eating more red meat actually causes breast cancer increases – decreasing meat consumption will only halve your risk of this type of cancer if you already eat the amount of meat in the highest red meat category. Those who eat one-and-a-half red meat servings per day (every day) will reap the biggest benefits from a lifestyle change to eating fewer than 3 servings per week. How big a benefit? Since we’re not given the rate of hormonally-related breast cancer among those who eat a lot of red meat, we simply can’t say.

What’s the take-home message? Premenopausal women who eat one-and-a-half servings of red meat per day could decrease their cancer risk by about half by going to fewer than 3 servings per week, but we don’t know how risky the heavy-meat lifestyle is. Instead of ordering up a steak from the grill, news consumers ought to order up more numbers from the press.


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