We know that this level and kind of fat intake may contribute to obesity, to hardening of the
arteries (leading especially to coronary heart disease) and to certain cancers, probably at least
large bowel cancer and breast cancer. But fat intake is certainly not the only factor in the
development of these diseases. The type of fat we eat seems to be just as important as the quantity.
While the intake of saturated fat should be limited, the presence of either monounsaturated or
polyunsaturated fat or both in the diet can be a healthy way of eating. Such food practices are
most common around the Mediterranean (where olive oil and fish are used) and in Scandinavia,
Japan and parts of China (where fish is traditionally used). In general, life expectancy is good in
these regions of the world and coronary heart disease rates are low. Of course, this is not to say
that the kind of fat eaten in those places is the only food factor, let alone lifestyle factor, of
importance. But it is worth identifying the common nutritional factors between these cultures as
far as fat intake is concerned.
How low should the fat intake go? Most current national recommendations are that fat should
only provide somewhere between 25 and 35 per cent of total energy or kilojoule intake. However,
there are those whose food culture requires (e.g., Papua New Guineans) and those who strive to
achieve (Pritikin dieters) fat intakes less than 10 per cent of energy. For some people with known
high blood cholesterol levels such an extreme change of diet may be necessary, but it is by no
means certain that this would be advisable for the general public.
It is of interest that as life expectancy has increased in Japan over the period 1965 to 1985 to become the longest in the world, the fat intake has actually gone up from about 15 to 20 to 25 per cent of energy. Perhaps we are now identifying an optimal level of fat intake. At the same time, many factors other than food will have contributed to increased life expectancy in Japan.