Reduced Fat Intake

Reduced Fat Intake in Foods and Breast Cancer Survival - How Foods Fight Cancer

Specific dietary factors appear to play key roles in cancer survival. First,
two studies of women diagnosed with breast cancer showed that those who
consumed 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.4,5 One of these studies identified benefits among premenopausal
women and 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 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.6 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.7–10 Some
studies have failed to confirm the dangers of fatty diets.11–14 However, most
evidence indicates that women consuming less fat tend to do better after
diagnosis, including the Women’s Intervention Nutrition Study (WINS),
sponsored by the National Cancer Institute (NCI).15 This study followed
nearly 2,500 postmenopausal women with breast cancer for five years after
their standard surgery and cancer treatments. Researchers instructed some
of them to continue their regular diets while the rest were put on a low-fat
diet. The women continuing their usual diets consumed an average of 51.3
grams of fat per day, which is still lower than the average American’s fat,
while the low-fat group averaged 33.3 grams per day—slightly more than
in a typical vegetarian diet. After five years, 12.4 percent of the women eating
their usual diet had cancer recurrences compared to only 9.8 percent of
the low-fat diet group, a 24 percent reduction in recurrence.

Why does low fat intake improve survival? To begin with, 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 and more fiber tend to have less estrogen
(independent of the difference in their body weight). They may also have
stronger immune defenses that can help them fight cancer cells.

Evidence suggests that diet changes must be substantial to be effective.
The Women’s Health Initiative included 48,835 participants, aged fifty to
seventy-nine, who were free of breast cancer, and tested a diet that emphasized
vegetables, fruits, and grains.16 Fat intake fell from 38 percent of
calories at the beginning of the study to 24 percent at one year, but slipped
back up to 29 percent at six years. After 8.1 years of follow-up, overall
breast cancer risk fell 9 percent, but the difference was not statistically significant,
meaning that it could have occurred due to chance. However, risk
of one type of breast cancer—progesterone receptor-negative tumors—fell
by 24 percent. While the study was not a survival study—it assessed the
risk of cancer developing in the first place, rather than the course of the disease
after diagnosis—it suggests that modest dietary changes may bring
only modest results.