12 Healthy Eating
on health through an interaction with a genetic predisposition. The effect
of both over- and underweight on health and diseases such as coronary
heart disease, hypertension, and cancer is discussed in chapters 8 and 10.
The impact of the actual composition of a person’s diet is described here.
Diet and coronary heart diseaseBefore the beginning of the twentieth century, coronary heart disease was
a rare condition. Its incidence increased steadily in Western countries
from 1925 to 1977 except for a dip during World War II. Since this time
its incidence has fallen dramatically in the US and Australia and has
fallen by about 25 percent in the UK (World Health Organization, 1994).
In contrast, Eastern European countries including Russia, Hungary, and
the Czech Republic have experienced an increase in coronary mortalities
in recent years. At this time, coronary heart disease remains the single largest
cause of death in the US and the UK. Although biological factors play a
part in coronary heart disease, diet is probably the fundamental factor.
This is clearly shown by incidence of the disease in immigrant groups.
For example, coronary mortalities are very rare in Japan, but Japanese groups
who move to the West quickly show the pattern of mortality of their new
environment (Syme et al., 1975). Coronary heart disease usually involves
three stages: 1) the development of atherosclerosis (narrowing of the
arteries); 2) a thrombosis superimposed on the atherosclerotic plaque (a
blood clot), and the impact of this, which can be sudden death, heart attack,
angina, or no symptoms; this depends on 3) the state of the myocardium.
Each of these three stages is influenced by different components of the diet.
Atherosclerosis
The material that accumulates in the arteries causing atherosclerosis is
cholesterol ester. Cholesterol ester exists in the plasma of the blood and is
higher in individuals with a genetic condition called familial hypercholes-
terolemia. Half of the cholesterol in the blood is biosynthesized by the liver,
and half comes from the diet. Diet influences blood levels of cholesterol
in two ways. First, blood cholesterol can be raised by saturated fat found
in animal fat and in boiled, plunged, or espresso coffee (not instant or
filtered). Secondly, blood cholesterol levels can be reduced by polyunsat-
urated fats found in plant oils; by soluble types of fiber such as pectin found
in fruit and vegetables and by oat fiber found in vegetables, oatmeal, and
oat bran; and by soya protein (Truswell, 1999).