Introduction
Cancer
is group of diseases with similar characteristics. Cancer
can occur in all living cells in the body and different cancer
types have different natural history. Epidemiological studies
have shown that 70-90% of all cancers are environmental. Lifestyle
related factors are the most important and preventable among
the environmental exposures. Tobacco consumptions either as
chewing tobacco or smoking tobacco will account for 50% of
all cancers in men. Dietary practices, reproductive and sexual
practices etc will account for 20-30% of cancers. Appropriate
changes in lifestyle can reduce the mortality and morbidity
from a good proportion of cancer and heart diseases.
Diet:
The
causes of cancer in U.S.A. was estimated by Doll and Peto
in 1981. Tobacco was found to be responsible for 25-40% of
cancers and diet for 10-70% of cancers. In Kerala tobacco is
responsible for 505 of cancer and diet for 10-20%of cancers.
Dietary factors may be potentiating the role of other risk
factors. Most of the cancers have some relationships with
diet predominant among them are cancers of the upper aero
digestive tract (mouth, throat), oesophagus (food pipe and
lungs), stomach, large intestine, and breast cancer in women.
The
idea that nutrition is an important factor in cancer causation
is not new. Yong-He Yan living in Song Dynasty( 960-1279 AD)
thought that poor nutrition was a cause of the condition now
known as oesophageal (food pipe )cancer. Lambe in 1815 warned
against the danger of excess consumption of food in general
and meat in particular. Roger Williams in 1908 observed that
excessive feeding especially meat, deficient exercise and
probably lack of sufficient vegetable food are the predisposing
factors for cancer. In one of the earliest epidemiological
studies on record Orr 91933, who undertook a study in Travancore
on oral cancer identified low intake of vegetables and fruits
as risk factors. We have not moved far from these observations
as we enter into the 21st century.
The
role of diet takes special importance in countries like India
which are fast moving towards industrialization and westernization.
We had a predominantly plant based diet and with the advent
of western life style we are moving towards a diet rich in
animal proteins. This coupled with other habits like smoking
and alcohol will lead to increase in the chronic disease burden
especially cancer and cardiovascular diseases. Prompt action
has to be taken to spread the message of healthy life style
and dietary practices.
Epidemiological
Studies:
Descriptive
epidemiological studies and International correlation studies
have raised specific dietary hypothesis like meat consumption
and colon (large intestine) cancer. Studies on migrant populations
stressed the role of environmental factors more than genetic
predisposition. Japanese have the highest rate of stomach
cancer incidents and very low rates of colon cancer and breast
cancer. Among the Japanese who have migrated to the USA, their
stomach cancer rates have dropped considerably and the rates
of colon have increased to that of Americans. These observations
were followed by case control and cohort studies which also
identified high fat, meat consumption as risk factors and
a diet rich in fruits and green and yellow vegetables protective
against many cancers.
The
biologically active ingredients of the fruits and vegetables
are from the carotenoid family and they have substantial anti-cancer
properties. Intervention Studies have tried to get the advantage
of eating vegetables through supplementation of beta carotene,
the most active ingredient.
A study
on smokers in Finland infact enhanced the risk of lung cancer
among those who took regular supplements of beta carotene.
What nature provides in its fullness cannot be encapsulated
and there is no substitute for a wholesome healthy diet.
Cancer
in Kerala
Population
based cancer registries have provided reliable data on the occurrence
of cancer in the State. The rate of cancer occurrence in Kerala and in India is much lower compared to Western countries,
but the large population will give rise to a large number
of cancers. It is estimated that 35,000 new cancer cases occur
in Kerala in one year. Among males 50% of cancers in the mouth,
throat and lungs are caused by Tobacco and alcohol habits.
Among women tobacco related cancers are 15%.
Cancer
of the head and neck:
The
main risk factor for these cancers is tobacco and alcohol.
A diet rich in green and yellow vegetables has been shown
to offer protection against oral cancer. Avoidance of tobacco
and alcohol is the most important preventive action against
mouth, throat and lung cancers.
Cancer
of the stomach:
Japanese
had the highest rate of stomach cancer of the world and the
rates in Japanese migrants have dropped to very low levels
as that of Americans when they migrated to the United States.
This is clear evidence of the dietary pattern and risk of
stomach cancer. The advent of refrigeration has dramatically
reduced stomach cancer incidents as it has revolutionized food preservation. Consumption of large amounts of red
chillies, food
at very high temperatures and alcohol consumption are the
main risk factors for stomach cancer in Kerala.
Cancer
of the large intestine:
Heavy
consumption of red meat can lead to risk of colon cancer.
White meat such as that of poultry do not have this risk.
There is an international correlation in between the occurrence
of large bowel cancer and consumption of red meat. In South
India there is a trend towards increasing consumption of red
meat and this can lead to increased risk for large bowel cancer.
Cancer
of the breast in women:
A large
number of factors are identified as risk factors for breast
cancer. Late age at first pregnancy greater than 30 years,
single child, late age at menopause etc are some of them.
A high fat diet is also identified as a risk factor. Physical
activity is found to be protective for breast cancer. The
sudden changes towards affluent life styles have reduced the
physical activities to a minimum and increased the consumption
of diets rich in fat. High fat diets during the pubertal age
and obesity in the post menopausal age are risk factors for
breast cancer.
Regular
breast self examination by women themselves is a very good
way of detecting breast cancer in early stages. Detecting
a cancer when it is in the very early stage can improve the
cure rate from breast cancer. Mammography (X-rays of the breast
) is another way of detecting breast cancer that cannot be
palpated by hand.
Cancer
of the uterine cervix:
Early
age at first intercourse, multiple sexual partners, poor sexual
hygiene, repeated child birth etc are some of the reproductive
risk factors for cervical cancer. Improvements in the living
standards of women has resulted in a reduction in the incidents
of cervical cancer. Regular cervical cytology examination (pap smear) by all women who have initiated sexual activity
can prevent the occurrence of cervical cancer. This has been
successfully achieved in many European countries.
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