Diet can increase
the risk of heart disease in several ways. Eating foods that are high
in saturated fat, low in polyunsaturated fat and high in cholesterol
can raise the level of cholesterol in the blood. When the blood cholesterol
level is increased the risk of coronary heart disease is increased.
Another kind of blood fat (lipid) known as triglyceride can also be
elevated and increase the risk of heart disease. Conversely, when
relatively more fruits, vegetables and wholegrain cereals are eaten
the blood fats are lower.
High blood pressure
(hypertension) also increases the risk of heart disease, strokes and
kidney failure. Blood pressure is higher when sodium intake is high,
potassium intake (an element obtained mainly from plant foods) is
low, alcohol intake is high and there is excess body weight. Eating
too much, with consequent obesity, increases the risk of heart disease
by increasing the work of the heart, increasing blood pressure, and
increasing blood fats; obesity also increases the risk of diabetes.
Nutritional factors can also alter the 'stickiness' of some blood
cells, called platelets; this contributes to hardening of the arteries
and may result in a blockage of the artery. Some polyunsaturated fish
oils reduce the stickiness of platelets and may account for the rarity
of heart disease amongst fish-eating communities, such as the Eskimos.
As far as tumours
or cancers are concerned, a number of interesting food factors are
emerging from research. A food intake low in fat and cholesterol,
high in dietary fibre from wholegrain cereals, with plenty of vegetables
and little alcohol seems protective against large bowel (colon and
rectum) cancer. The reasons for this are not yet known. The same kind
of dietary pattern may also reduce the risk of tumours of lung, breast,
uterus, prostate and pancreas. There is little evidence so far to
suggest that food additives are significant in the development of
Diabetes is a
condition where the blood sugar (glucose) is too high because not
enough insulin is produced by the pancreas for the body's needs. The
glucose spills from the blood into the urine, leading to a large loss
of water as urine; thirst then follows. Broadly there are two types
of diabetes, one where it is necessary to administer insulin from
the time of diagnosis and the other where it is not. Amongst Caucasians
in industrialized nations two to three people in every 100 are affected.
When non-Caucasians adopt the food habits of affluent society, they
appear to be particularly susceptible to diabetes; from 15 to 40 per
cent of Australians of Aboriginal or Pacific-Islander descent suffer
from diabetes. Being overweight is a particularly important risk factor
for developing the type of diabetes where administered insulin is
not usually needed. A diet with a high intake of high-carbohydrate,
high-dietary-fibre foods and a low intake of fat seems protective
against the development of this type of diabetes.
Since most premature
deaths in affluent societies result from atherosclerotic disease of
blood vessels (vascular disease), and from lung, breast and large
bowel cancer, there is great potential for dietary change to increase
life expectancy and, indeed, to reduce morbidity and chronic illness.