How Diet Influences
Diet is a double edged sword. Improper
diet increases the risk of cancer but a proper, well
balanced diet reduces the cancer risk.
Diet is one of the most important lifestyle factors and
has been estimated to account for up to 80% of cancers of
the large bowel, breast, and prostate. Diet affects the risk
of many other cancers, including cancers of the lung,
prostate, stomach, esophagus and pancreas.
High consumption of meat, especially red meat,
substantially increases the risk of prostate cancer.
Vegetables, especially cooked tomatoes, reduce the risk
of prostate cancer. In one clinical trial, the role of
Vitamin E as a prostate cancer reducing factor was
established. In this study there was a 32% decrease in
prostate cancer incidence and 41% decrease in prostate
cancer mortality in people receiving Vitamin E supplements
when compared to controls.
In Japan, people consume Tofu, a soya product. It
contains isoflavones that moderate the estrogen receptors in
the body such as breast tissue. The incidence of breast
cancer is low in Japan when compared to Western women; only
1/4th of the mortality rate of Western women. Japanese
women's low fat diet, high fish consumption and drinking
green tea also decrease their breast cancer risk.
One case control study found that regular consumption of
soy foods was associated with a marked decrease in breast
cancer risk in premenopausal women. No effect in
A Japanese case-control study also found that tofu intake
(3 times/wk compared with less than 3 times/wk) was
associated with decreased risk of breast cancer in
premenopausal women. Again, soy intake was not protective
against post-menopausal breast cancer.
In one study conducted in America, the relation between
soy intake and breast cancer risk found that tofu
consumption was protective in both premenopausal and post
menopausal Asian women.
Lung cancer risk is substantially decreased by a variety
of carotenoids. Carotenoids act as antioxidants and thus
minimize cell damage.
One study in Boston focused on the effect of different
types of carotenoids on lung cancer risk. It was observed
that lung cancer risk was significantly lower in subjects
who consumed a diet high in a variety of carotenoids. This
was especially true with non-smokers who had 63% less risk.
One study conducted in Hawaii reported further evidence
for a protective effect from certain carotenoids against
lung cancer and that greater protection was afforded by
consuming a variety of vegetables compared to only foods
rich in a particular carotenoid.
Nitrates in food and other preservatives added to food
including meat are converted into 'nitrites' in the human
stomach. The nitrites undergo nitrosation to form
'nitrosamines' and 'nitrosamides'. This increases the risk
of stomach cancer in people eating vegetables from nitrate
In one study, Vitamin C appeared to protect against the
risk of stomach cancer by inhibiting formation of nitrates
Cancer of the stomach is 5 times more common in Japanese
people compared to Western populations. When Japanese people
migrated to the United States, they progressively acquired
the low incidence of the US due to changes in their diets.
In one study conducted in Hawaii that involved both
Japanese and Caucasians, the stomach cancer risk was
associated with consumption of rice, pickled vegetables, and
dried/salted fish, and a negative association with vitamin C
One ecological study in Belgium showed a relation between
the nitrate and salt consumption and stomach cancer. The
analysis of this model showed that the significance of
nitrate as a risk factor for stomach cancer mortality
increased markedly with higher sodium levels.
Dietary habits and stomach cancer risk was studied in
Shanghai, China. According to this study, risks of stomach
cancer were inversely associated with high consumption of
several food groups, including fresh vegetables and fruits,
poultry, eggs, plant oil, and some nutrients such as
protein, fat, fiber, tea and antioxidant vitamins.
By contrast, risks increased with increasing consumption
of dietary carbohydrates, frequent consumption of preserved,
salty or fried foods and hot soup/porridge, with irregular
meals, speed eating and binge eating. This provides evidence
that diet plays a major role in stomach cancer risk.
No single food can completely prevent cancer but a
balanced combination of different groups can help.
Appropriate diet can prevent 3-4 million cancers each year.
Cancer is One of the Main Causes of Death Among Humans.
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