|
Women
& Cancers: Opportunities for Prevention
 By
Neal D. Barnard, M.D.
Ask any doctor what women can do to prevent breast cancer, and the
response will probably be to get an annual mammogram after age 50,
or perhaps after age 40. Mammograms certainly are important. But
they do not prevent cancer. They find cancer. Biopsy, surgery, or
chemotherapy then follow.
What is largely unknown to the American public—and sadly
underemphasized in medical schools—is that breast cancer is often a
preventable illness. When I was a medical student, I was not taught
that breast cancer had any relationship to dietary factors. At that
time, breast cancer attacked 1 in every 11 women. When I was a
resident in the early 1980s, most doctors remained ignorant of any
risk factors that could be controlled, and the rate went up to one
in ten. The failure to prevent cancer has exacted an increasing
toll; today, the disease attacks one woman in eight.
It is not that scientists do not have the information. As long ago
as 1982, the National Research Council published a report called
Diet, Nutrition, and Cancer,1 showing the mountain of evidence
already available linking specific dietary factors to cancer of the
breast and other organs. But brochures with watered-down
recommendations have sat collecting dust at cancer research centers.
There was never an organized effort to give women the information
they need to make decisions about cancer prevention.
The dietary factors emerged in comparisons of different countries.
In Japan, for example, breast cancer is rare. But Japanese women who
move to the United States soon have the same risk of cancer as
American women—at least 400 percent higher than in Japan. The
differences in cancer risk between the U.S. and Japan are not due to
genetics. Nor is it something in the air or water. The critical
factor is the amount of fat, particularly animal fat, in the diet.
In Japan, only about 15 percent of the calories in the diet come
from fat. In the U.S., the fat content of the diet has been more
than two times higher, around 35 percent. The more fat women
consume, the greater their cancer risk. Similar findings have been
made within other countries.
When the link between fat and cancer was found, researchers did not
have to look far for an explanation. Several possibilities presented
themselves. First of all, it is known that many breast tumors are
"fueled" by estrogens, the female sex hormones for both women and
men. But the more estrogen there is, the greater the driving force
behind some kinds of breast cancer. The principal estrogen is
estradiol, and the amount of estradiol produced by the body is
linked to the amount of fat in the diet. On high-fat diets,
estradiol production increases. On low-fat diets, it decreases. When
women first adopt low-fat diets, their estradiol levels drop
noticeably in a very short time. Vegans (people who consume no
animal products) have significantly lower estrogen levels than
non-vegetarians, perhaps because of the lower fat content of the
vegan diet.
In addition, estradiol is carried in the blood on special carrier
molecules. On high-fat diets, more estradiol breaks free from its
carrier molecules and becomes biologically active, like soldiers
jumping off a jeep and starting their attack. So high-fat diets may
promote cancer by increasing the amount in addition to promoting the
biological activity of estradiol in the body.
continued...
Source: Physicians Committee for Responsible Medicine |
