Encyclopedia of Health and Medicine

382 Cancer
lifestyle and cancer Personal factors that may
contribute to the prevention or the development
of cancer. The most significant lifestyle factors
related to cancer are smoking, diet, OBESITY, and
exposure to environmental carcinogens.
Smoking and Other Tobacco Use
Cigarette smoking accounts for 87 percent of LUNG
CANCER in the United States, making lung cancer
one of the most preventable types of cancer. Cigarette
smoking also raises the risk for numerous
other types of cancer, including oral cancer, laryngeal
cancer, ESOPHAGEAL CANCER, STOMACH CANCER,
LIVER CANCER, COLORECTAL CANCER, PANCREATIC CAN-
CER, kidney cancer, BLADDER CANCER, PROSTATE CAN-
CER, BREAST CANCER, and CERVICAL CANCER. Cigar
smoking increases the risk for oral cancers (cancers
of the MOUTH and lips) as well as lung cancer,
pharyngeal cancer, and stomach cancer. Other
tobacco use, such as chewing tobacco and snuff, is
the primary cause of oral cancers. Not using any
form of tobacco removes its risk as a cause of
cancer.
Diet and Nutrition
Numerous studies indicate a diet high in fruits,
vegetables, and whole grains and whole grain
products reduces the risk for most cancers overall
and specifically for esophageal cancer, stomach
cancer, and colorectal cancer. Researchers believe
the NUTRIENTS, antioxidants, and fiber are the key
substances that lower cancer risk. Nutrients and
antioxidants boost the IMMUNE SYSTEM, improving
its ability to detect and eliminate abnormal cells
early in their development. Fiber helps absorb toxins
in the gastrointestinal tract and move them
more rapidly through the digestive process.
Conversely, research demonstrates that a diet
high in red meat increases the risk for cancer
overall and specifically HORMONE-DRIVEN CANCERS
and cancers of the gastrointestinal tract. Red meat
is the primary dietary source of saturated fats,
which the body uses to synthesize (make) steroid
hormones (androgens and estrogens). These hormones
fuel the growth of some types of cancer
cells in breast cancer, OVARIAN CANCER, ENDOMETRIAL
CANCER, and prostate cancer. Whether they may
also encourage the development of these cancers
remains under investigation.
Some research has established a connection
between the length of time food remains in the
gastrointestinal tract with the risk for colorectal
cancer. A diet high in plant-based, high-fiber foods
moves through the digestive process more quickly
than a diet high in fat. Some studies show a primarily
plant-based diet may move through the
body in 6 to 8 hours, while a high-fat, low-fiber
diet may take as long as 26 hours to make the
digestive journey.
Obesity
The risk for numerous cancers rises with OBESITY.
The reasons for this are difficult to separate out.
Researchers know that regular physical activity
and nutritious EATING HABITS support the health of
cells throughout the body as well as foster efficient
immune function. These factors are generally
lacking in obesity. Further, the increase in adipose
tissue prevalent in obesity appears to be a contributing
factor to hormone-driven cancers such as
prostate cancer and breast cancer, the risks for
which are higher in people who have obesity than
in people who are of healthy weight.
Exposure to Environmental Carcinogens
Researchers have identified more than a thousand
chemicals and other substances that have the ability
to cause cancer. Some become hazardous only
with repeated excessive exposure over time, and
some have a fairly immediate consequence.
Chemical exposures are common causes of THY-
ROID CANCER, LEUKEMIA, and LYMPHOMA. The ultraviolet
rays of sunlight are perhaps the most
common long-term environmental CARCINOGEN,
responsible for nearly all SKIN CANCER. Radon,
which is present in the soil as a byproduct of deteriorating
uranium and other radioactive minerals
that occur naturally, is the second-leading cause of
lung cancer. RADIATION THERAPY as treatment for
cancer is also a carcinogen, raising the risk for
lymphoma as well as solid tumors.
Lifestyle Modifications to Decrease Cancer Risk
Nutritious eating habits, daily physical exercise,
and avoidance of tobacco products are key ways in
which people can modify their lifestyles to reduce
the risk for cancer as well as other significant
health conditions such as CARDIOVASCULAR DISEASE