Nutritional disorders

Abstract

The normal diet contains 2500–3000 calories (10.5–12.6 MJ) daily — the dietetic calorie is in fact a kilocalorie, 1000 times a chemical ‘calorie’. Of the daily calorie intake 40–50% is derived from carbohydrate, about 12% from protein, and 42% from fat in Western countries. It will be remembered that 1 g of carbohydrate or protein produces four calories, and 1 g of fat nine calories. Thus an average diet contains 350–400 g carbohydrate, 70–90 g protein and 110–140 g fat. A mixed diet supplies adequate minerals (salt, potassium, calcium, magnesium, iron), trace elements such as iodine, and vitamins. The relative excess of carbohydrate, especially refined carbohydrates such as sugar and the lack of dietary fibre has been blamed for many of the ills of civilized society — especially diabetes and arteriosclerosis but also diverticular disease and colonic cancer. Dental caries is related to a high sugar and sweet intake. Too much animal fat in the diet is associated with a raised cholesterol level and possibly a raised incidence of arteriosclerotic coronary disease. The substitution of polyunsaturated vegetable oils for animal fats lowers the blood cholesterol (and has been recommended in the USA) but it has yet to be shown that this prevents coronary disease. Again, although there is no absolute proof of the many advantages claimed for dietary fibre there is a growing body of opinion that the fibre content of the diet should be increased and a return made to a more natural diet including bran, wholemeal bread and vegetables including potatoes.