Kidney Stones
What is it?
Kidney stones are usually made up of crystals of calcium oxalate, either alone or in combination with calcium phosphate. They can be found in the kidney itself or anywhere in the duct (ureter) that carries urine from the kidney to the bladder. Kidney stones can be as small as a tiny pebble or an inch or more in diameter. The compounds from which stones are formed are normally present in human urine but remain in solution due to control of acidity and the presence of various protective compounds. When these protective mechanisms are overwhelmed, stones may be allowed to form. There are usually no symptoms until the stone blocks the urinary tract resulting in excruciating pain until the stone passes. The rate of occurrence of kidney stones is increasing, and over 10 per cent of men and 5 per cent of women experience at least one kidney stone during their lifetime.
Causes of kidney stones
Although there are many types of kidney stones, the most common type contains calcium and occurs due to alterations in calcium metabolism, including absorption from the intestine, filtering from the kidneys or abnormalities in the hormones that regulate the use of calcium in the body.
Treatment of kidney stones
Treatment depends on the size, symptoms, location and cause of the kidney stone. If the stone is small and can be passed, drinking plenty of fluids may be enough. For kidney stones too large to be passed, a procedure known as lithotripsy is often used. During this procedure, shock waves are directed to the areas where the stone is located. The shock waves break it into fragments. After the treatment, the patient drinks a lot of water to flush out the stone fragments.
Kidney Stones and diet
Diets which are low in fiber and high in refined carbohydrates, alcohol, animal protein, fat and salt lead to an increased risk of kidney stones. High intakes of calcium and vitamin D-enriched foods may also increase the risk. Vegetarians appear to have a decreased risk of developing kidney stones, as their diets are usually lower in protein and higher in green vegetables and grains. Drinking plenty of water can be a useful preventive measure.
Eating an alkaline diet that includes potatoes, vegetables and fruit (but not citrus fruit), and reducing protein intake will help to reduce the risk of uric acid stone recurrence. Some experts advise limiting intake of liver, kidneys, fish roe and sardines as these foods are high in purines which may contribute to stone formation.
To reduce the risk of calcium oxalate stones, it is helpful to avoid foods containing oxalates, such as spinach, rhubarb, beet, parsley, sorrel, and chocolate. People who have a tendency to form oxalate stones often secrete too much calcium in their urine, which reacts with oxalic acids to form the stones. In such people, calcium and sodium intakes should not be too high and restricting intake of dairy products is likely to be beneficial.
Vitamins, minerals and kidney stones
Vitamin B6
Vitamin B6 deficiency may also play a role in the development of some kinds of kidney stones. Combined magnesium and vitamin B6 treatment may bring more beneficial results in the treatment of kidney stones than the use of magnesium alone. Vitamin B6 reduces the production and excretion of oxalates, compounds that combine with calcium to form some types of kidney stones.1
Vitamin C
There have been reports that excess vitamin C may increase the risk of kidney stone formation as large doses may raise blood levels of oxalates and lead to increased excretion. However, healthy people do not seem to be at risk.2 Those suffering from kidney disease, gout, or who are on hemodialysis may be at increased risk and should avoid large doses of vitamin C.
Vitamin K
Vitamin K is necessary for the production of a urinary protein involved in kidney function that inhibits the formation of calcium oxalate kidney stones.3 This may account for the fact that vegetarians, whose diets are often high in vitamin K, have a low incidence of kidney stones.
Calcium
Some forms of calcium supplements may lead to an increased risk of kidney stones. This risk can be lowered by using supplements in calcium citrate form. Citrate levels are lower in kidney stone patients, and citrate supplementation has been shown to reduce stone crystallization.
Magnesium
Magnesium deficiency may play a role in kidney stone formation as magnesium increases the solubility of calcium oxalate and inhibits the precipitation of calcium phosphate and calcium oxalate. Kidney stones are frequently associated with low levels of magnesium in the urine, although the exact effects of this abnormality are not well understood. Magnesium citrate supplements may be the most beneficial type to use to reduce the incidence of kidney stones.
The results of a 1997 study suggest that magnesium supplements may be beneficial in preventing kidney stones. Researchers found that giving potassium-magnesium citrate to calcium oxalate kidney stone sufferers reduced the risk of them developing further stones. In the double-blind study reported in the Journal of Urology, 64 patients were given either a placebo or the potassium-magnesium citrate compound for up to three years. New kidney stones occurred in 63.6 per cent of the patients taking placebo but in only 12.9 per cent of those taking the potassium-magnesium citrate compound.4
Herbal medicine and kidney stones
Useful herbs include pellitory of the wall (Parietaria officinalis), couch grass (Agropyron repens), nettles (Urtica dioica), gravel root (Eupatorium purpureum), corn silk (Zea mays), golden rod (Solidago virgaurea) and stone root (Collinsonia canadensis).