Foods and Breast Cancer Survival

Healthful diets not only help prevent cancer; they also improve survival when cancer has been diagnosed. The first clues that foods might affect the course of breast cancer came from studies of women in Japan in the early 1960s. Compared to Western women, Japanese women were much less likely to develop the disease and much more likely to survive it if it occurred. Over the next several decades, researchers have followed up on these observations to try to clarify what is the best diet for cancer survival. Although this work is still in its early stages, important information has already come to light.

One of the best-established factors affecting breast cancer survival is body weight. Women with breast cancer who are near their ideal body weight at the time of diagnosis are more likely to survive than are women with higher body weights. And although weight gain often occurs after diagnosis, studies suggest that women who avoid weight gain after diagnosis tend to have longer diseasefree survival.

The link between lower body weight and better survival may relate to estrogens, female sex hormones that can encourage the growth of cancer cells. In essence, body fat acts like an estrogen factory, producing estrogens from other compounds coming from the adrenal glands (small organs situated atop each kidney). As a result, women with more body fat tend to have higher amounts of estrogens circulating in their blood, compared to leaner women.

Reduced Fat Intake Specific dietary factors appear to play key roles in cancer survival. First, two studies of women diagnosed with breast cancer showed that those who had been consuming less fat prior to diagnosis generally had smaller tumors with less evidence of cancer spread, compared to women whose diets had included more fatty foods. One of these studies identified benefits among premenopausal women; the other, among postmenopausal women.

Studies that have followed women for several years after diagnosis have generally found that those with less fatty diets prior to diagnosis live longer than other women. In one of the first such studies, researchers at the State University of New York in Buffalo, N.Y., found that women with advanced cancer had a 40 percent increased risk of dying at any point in time for every 1,000 grams of fat they consumed per month. Note that this does not mean a person’s risk of dying is 40 percent. It means that, if a person’s diet contains an extra 1,000 grams of fat per month at the time of diagnosis, that person’s risk of dying is 40 percent higher than it would otherwise have been. There is, of course, tremendous variation from one woman to another, so this figure is simply an overall observation drawn from the group of participants. To make this more concrete: The difference between a typical American diet and a low-fat, vegan diet is approximately 1,000–1,500 grams of fat per month, which corresponds to a 40–60 percent difference in mortality risk at any point in time.

Other studies found much the same thing—fatty diets are associated with increased risk, and that is particularly true for saturated fat, the kind that is common in meat, dairy products, eggs, and chocolate. Some studies have failed to confirm the dangers of fatty diets. However, most evidence indicates that women consuming less fat tend to do better after diagnosis.

Why should a low fat intake improve survival? For starters, low-fat diets tend to be modest in calories, since fats and oils are the densest source of calories of any food we consume. In fact, some investigators believe that the main problem with fatty diets is simply their high calorie content. In addition, women who eat less fat tend to have less estrogen coursing through their veins (independent of the difference in their body weight). They may also have stronger immune defenses that can help them fight cancer cells.

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