SELF-HELP PREVENTION: KIDNEY STONES
What they are?
Stones made of calcium salts that are produced by and lodge in the kidney. Some stay there and produce no symptoms for years and others pas down the tube (the ureter) that leads from the kidney to the bladder, causing great pain as they do so. Such stones hospitalize more than million North Americans each year. Many millions of others have small stones which pass without being noticed or with only a small amount of abdominal or loin pain.
What causes them?
The fluids that pass through the kidneys contain many different chemicals and minerals. Two of the more plentiful of these are calcium and oxalate, which combine to form calcium oxalate. If there is too little fluid or too much of these salts they begin to settle out and crystallize. More crystals are attracted until, like a snowball, the deposit increases in size and becomes a small, hard stone. This in turn can grow in size to almost fill the cavity of the kidney.
Just what starts off this crystallization process is not known but it is thought that a tiny piece of organic matter such as a bacterium could do so.
The population appears to be divided into two broad categories-stone-formers and non-stone-formers. An analysis of 24-hour urine collections from stone-formers shows that between 40 and 60 per cent has too much calcium in their urine. One study found that stone-formers ate more purine-containing foods and another found that they consumed more meat, fish and poultry and less bread, grains and starch. Research shows that both protein and glucose increase the rate of calcium excretion in the urine and that the glucose effect is exaggerated in stone-formers. This led one researcher to claim that kidney stones are a disorder of carbohydrate metabolism. Adding sugar to the diet increases the amount of calcium put out in the urine.
Another feature of the diet of the countries in which kidney stones are common is the amount of animal protein they eat. Research has found that the more animal protein we eat the more oxalate and calcium we excrete into our urine.
Dietary fibre traps and reduces the absorption of sugars, and wheat bran definitely produces beneficial effects on carbohydrate metabolism and the control of blood sugar. One study found that wheat bran reduced the absorption of calcium from the diet by as much as 50 per cent and that the increased absorption of calcium normally produced by sugar was reduced in those taking bran.
A study in Ireland, where 8 per cent of the population has a kidney stone at some time in their lives, found that the diet of fifty-one stone-formers was different from those who never formed stones. The stone-producers ate less fibre, got fewer carbohydrates from fruit, vegetables and grains and ate more fat and red meats.
An Australian study compared thirty meat-eaters with thirty vegetarians and found that the animal proteins caused an abundance of calcium to be excreted into the urine. They also found that the lower the calcium intake, the higher the oxalate excretion, so clearly reducing calcium intake alone is no good if you have kidney stones-you need to reduce your oxalate level as well.
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