Fueling Up on Low-Fat Foods

Fueling Up on Low-Fat Foods - How Foods Fight Cancer

Estrogen not only makes normal tissues grow; it can also make cancer
cells grow. Although researchers have long known that estrogens encourage
the growth of cancer cells once they form, evidence also suggests that they
can also spark the very first step in cancer development: the transformation
of healthy cells into cancer cells. Specifically, enzymes in the body alter
estrogens to produce other molecules that can damage DNA, leading to
cancer. When researchers add a bit of estrogen to breast cancer cells in a
test tube, they multiply rapidly.1 In fact, one of the main goals of breast
cancer treatment is to reduce estrogen’s effects (using drugs, such as tamoxifen,
that block estrogen’s activity).

Here is where diet comes in. Foods influence estrogen’s effect, too—to a
striking degree. When a woman begins a low-fat, high-fiber diet, the amount
of estrogen in her blood drops almost immediately. In a matter of weeks, the
amount in her bloodstream drops by 15–50 percent.2,3 She will still have
more than enough estrogen for fertility, but she will nonetheless have less
estrogen than before. From the standpoint of cancer prevention, that’s a
good thing. It means there will be less stimulus for cancer cell growth.

A 2003 study published in the Journal of the National Cancer Institute
found that when girls aged eight to ten reduced the amount of fat in their
diets—even very slightly—their estrogen levels were held at a lower and
safer level during the next several years. When the girls increased their
intake of vegetables, fruits, grains, and beans, and reduced their intake of
animal-derived foods, the amount of estradiol (a principal estrogen) in their
blood dropped by 30 percent compared to a group of girls who did not
change their diets.4

The same phenomenon occurs in men. Men have estrogen in their
blood, too—although much less than women have—and cancer researchers
have long suspected that both estrogen and testosterone (the “male hormone”)
play roles in prostate cancer risk. But as men cut the fat and increase
fiber in their diets, the amounts of both estrogen and testosterone tend to
fall. Don’t worry—this change does not make a man any less masculine. But
it may well reduce the hormonal stimulus for prostate cancer growth.

Because of these and related findings, many researchers have suggested
that steering clear of meat, dairy products, fried foods, and other fatty fare
may reduce cancer risk. However, it is important to understand that, in
order to reduce cancer risk or effectively alter its course, dietary changes
have to be significant. Studies have shown that modest changes in diet do
little or nothing. For example, in the Women’s Health Initiative study,
nearly 25,000 women in the intervention group were instructed to consume
a low-fat diet (aiming for no more than 20 percent of calories from fat) for
eight years.5 However, the inclusion of naturally high-fat meat and dairy
products in the diet made it difficult for participants to meet the moderately
low-fat requirement and show any signs of cancer risk reduction. By the
end of the study, these women were averaging 29 percent of calories from
fat, compared to the control group, which averaged 35 percent of calories
from fat. This modest difference resulted in only small changes in breast
cancer risk reduction.