Q:Are there any alternative ways to treat or prevent kidney stones from recurring? D W, New Haven, Connecticut.......
A:Nutritional expert Dr Stephen Davies recommends that a first port of call for any stone former is to have your blood calcium levels measured to see if they are elevated. If so (as it is in about 15 per cent of stone formers), you may have an abnormality of the parathyroid glands (which control calcium metabolism), which might require treatment for surgery.
But if not, and if other numerous blood and urine investigations are normal, showing no underlying kidney disease, our American panelist and nutritional expert Dr Melvyn Werbach, says there are a number of foods that people prone to kidney stones should avoid. Chief among these is animal protein, which increases calcium and oxalate loss and also the excretion of uric acid, and fat in general, which is consumed in greater quantities by people who get kidney stones.
You should also limit sugar in your diet, which also promotes loss of those factors linked to the formation of stones, as well as caffeine. Although the oxalate in your diet makes only a modest increase in the oxalate in your urine, Dr Werbach advises people whose urinary oxalate is high to limit high oxalate foods, which include beans, cocoa, instant coffee, parsley, rhubarb, spinach and tea.
Other foods relatively high in oxalates include carrots, celery, chocolate, cucumber, grapefruit, kale, peanuts, pepper and sweet potatoes.
In Healing through Nutrition (HarperCollins, NY, 1993), Dr Werbach suggests that you eat more fibre (which stone formers tend to lack. Several studies show that added fibre can reduce the excretion of calcium in the diet, he says, by up to 40 per cent (Urol Res, 1984; 12: 58). He also recommends that you consider embarking on a vegetarian diet. Make sure you have enough fluids (two quarts a day), unless you have a problem with water retention. Steer clear of sugar, salt, alcohol and caffeine.
Dr Werbach has also discovered that stone formers tend to be deficient in a number of nutrients. Chief among these can be minor deficiencies in vitamin B6, which is needed to break down the oxalic acid in the body. When oxalic acid accumulates, it is more likely to form calcium oxalate. Studies have shown, he says, that stone formers with proven excess oxalic acid in the urine do respond to vitamin B6 supplements, even those without a demonstrable deficiency. Dr Werbach recommends 40 mg as a daily dosage.
Because vitamin C can break down to oxalate, medicine has blamed stone formation on supplementing with high doses of ascorbic acid. Two studies (one in guinea pigs) provide contradictory evidence about this. Kidney disease patients given doses of 500 mg or more of vitamin C showed a statistically significant increase in urinary oxalate (J Urology, May 1992). However, two sets of animal experiments with guinea pigs found that even high doses of vitamin C did not induce stones in healthy animals, but only those with hypercalciuria (Scan Microsc, September 1993). But Dr Werbach says that most other evidence shows that urinary oxalate only increases on megadoses of 6 gms or more a day. If for some reason you have to take that size daily dose, he recommends that you take it with B6, which will tend to reduce the increase in urinary oxalate.
As for calcium, studies have shown that even high daily supplements of calcium up to 2 gm a day don't increase urinary calcium so long as your vitamin D levels are normal. One study found no relation between stone formation in premenopausal women and taking supplements of calcium citrate.
In fact, restricting calcium doesn't usually cut down the calcium levels in your urine, since it has to do, in many stone formers, with the overproduction of vitamin D. Paradoxically, urinary oxalate increases if dietary calcium is reduced (Br J of Urol, 1982; 54 (6): 590-3).
This may be of interest to women who take high doses of calcium to prevent osteoporosis (although they do better looking to improve magnesium levels see WDDTY vol 4 no 11). If you are taking calcium supplements, Dr Werbach recommends that you take it as calcium, citrate, gluconate or lactate, which decrease the amount of calcium excreted.
Speaking of magnesium, Dr Werbach says that low magnesium may be a cause of kidney stones; magnesium in the urine tends to combine with oxalate to form magnesium oxalate, a harmless form of it. He suggests at least 300 mg per day with foods. He also recommends potassium rich foods and generous portions of potassium citrate (a natural source is cranberry juice).
One study has linked stones to the free radicals in the Western diet. Animal studies have shown that fish oils could prevent the formation of stones without side effects (J Urol, July 1991).
It's also important to check your body's level of cadmium, high levels of which can contribute to stone formation. If it is high, you can lower it through zinc supplementation and a low-protein diet.