PREVENTIVE MEDECINE: KIDNEY STONES
The incidence of kidney stones has gone up considerably this century. It used to be mainly an adult disease but now it occurs in children too. The occurrence rate is between 3 and 13 per cent in westernized countries, with the rate in the USA about 12 per cent, yet kidney stones are rare in people living in poor or primitive conditions.
What could have caused such a change? The greatest difference between the poor and the affluent countries of today is their diets. In the richer countries, the fat and animal protein content of the diet is five times greater than in the typical diet of the poorer countries. Most kidney stones are made of calcium and it is known that both protein and glucose can increase the amount of calcium the body puts out in the urine. One researcher has found that the glucose effect is exaggerated in stone-formers. Sugar can be shown to increase the amount of calcium put out by the kidneys in normal people and to produce damage to the tubular cells of the kidneys of animals.
It has been found that people who repeatedly form kidney stones eat more animal protein than do other people. The stone-formers in one study consumed more meat, fish and poultry and less grain and starch than did non-stone-formers. A high-fibre diet might well be of value in this condition in so far as it reduces blood-glucose swings-which are known to be critical in producing a urine rich in calcium, which then crystallizes out to form kidney stones. Lastly, there is evidence that a western diet reduces the production of normal stone-inhibiting substances in the urine.
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