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Aside from diet, other factors increasing risk of breast cancer
include:
Hormones
Oral contraceptives appear to increase
risk. Although newer birth control pills contain less estrogen and
progesterone than older versions, evidence suggests some increase
in risk from oral contraceptives.44 The same may be true
of supplemental hormones given to women after menopause.45
In both cases, it makes sense for women to discuss the risks and
benefits with their personal physicians.
Overweight
Higher body weight increases the risk
of breast cancer after menopause.46 Before menopause, weight does
not increase risk.
Radiation
Of all the different parts of the body,
the breast is probably the most sensitive to X-ray damage, and there
is no doubt that X-rays to the breast can cause cancer.47
This raises obvious concerns about mammograms, which, after all,
are X-rays. Overall, evidence suggests that annual mammograms are beneficial for women over
50. But women should schedule mammograms only at modern facilities
that do them regularly and maintain new equipment, keeping radiation
doses to a minimum. Below age 50, scientific studies are less clear as to benefits from routine mammograms. The reason is that many
cancers are missed on mammograms, and women have sometimes been
falsely reassured by a negative mammogram, leading to delays in
diagnosis and treatment. Before age 50, routine mammograms do not
improve on the power of physical (and self) examination.
In addition, it is also important to keep in mind that mammograms are a means of screening, not prevention. For information on breast cancer prevention, visit Breast Cancer: Prevention and Survival.
Genetics
About 5 percent of breast cancer cases
are purely attributable to genetics.48 In such cases,
cancer is passed from parent to child as a dominant trait, and the
family tree is riddled with the disease. And for a larger group
of individuals, genetics probably makes a contribution in subtle
ways. For example, it may well be that different genes influence
one's susceptibility to carcinogens, the strength of the immune
system, body weight, and other factors. Each of these is also influenced
by diet.
Time between Puberty and First Pregnancy
The
younger a girl is when puberty occurs, the higher her risk of breast
cancer. Also, the later the age of her first pregnancy, the higher
her risk. It may be that the early age of puberty simply indicates
elevated hormone levels, as was described above. As high-fat, low-fiber
diets have spread from the wealthy part of the population to, now,
the entire population, the age of puberty has dropped dramatically
from age 17 in 1840 to 12.5 today. Similarly, as Japan's diet has
westernized since World War II, the age of puberty has dropped from
15 to 12.5. It may be that early puberty and cancer are both the
result of a hormonal aberration.
The time period between puberty and the first pregnancy is one
in which the body may be particularly sensitive to carcinogens,
and the longer this time period is, the greater the risk.
References
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