|This month, I conclude this two-part series on nutrition and kidney stones, based on a recent study by Bhandari and Menon.1 [Editor's note: Part one of this article appeared in the Nov.4 issue.]|
Malabsorption in the small intestine reduces calcium in the intestinal lumen to a level at which it is insufficient to bind with oxalate; thus, oxalate levels rise and, in the kidney, bind with calcium and cause stone formation. Nutritional support includes increased fluid consumption (to a level at which at least 64 ounces of urine are produced per day), increased calcium carbonate (500 mg TID - 1,500 mg total), increased vitamin B6 (100-150 mg per day), increased tyrosine, decreased dietary oxalate, and decreased dietary fat. If calcium carbonate is consumed with each meal, it will bind with oxalates, thus reducing urinary levels. Vitamin B6 may reduce oxalate levels in the urine by reducing endogenous synthesis. Tyrosine can also reduce oxalate synthesis by blocking the conversion of hydroxyproline to oxalate. If dietary calcium is low or restricted, the body will tend to eliminate oxalates via the urine, which is problematic in oxalate stone formers.
Uric acid can promote calcium oxalate kidney stone formation in some people. Those who are susceptible to hyperuricosuria almost always consume a high purine diet. Nutritional support includes reducing consumption of dietary beef, pork, poultry and fish. Bhandari and Menon state that in these types of cases, getting a meat eater to become almost vegetarian can be very difficult. Often these people will prefer to eat their meat and take medicine to decrease uric acid synthesis.
Hypocitraturia is most often associated with patients who suffer from urinary tract infections or are acidotic. Kidney resorption of citrate is elevated. Nutritional therapy includes eating more alkaline foods (most fruits and veggies) and less acid foods (beef, beans, beer, coffee, cocoa, vinegar and grains). Sodium bicarbonate (300mg/kg/bw or 135 mg/lb/bw) may also be used to promote an alkaline environment. Sixty-four ounces of fresh lemonade daily can be substituted for the bicarbonate, and used with it in tough cases.
Hypomagnesuria is most commonly seen with patients who suffer from inflammatory conditions of the gastrointestinal tract. Inflammation reduces the absorption of magnesium. When magnesium levels are deficient, there is no antagonist to prevent calcium and oxalate from crystallizing. Nutritional therapy is magnesium, 200 mg twice daily. Citrate is the preferred form, but it is not the only form that will work.
Renal Tubular Acidosis
This syndrome is the result of a kidney disorder, whereby hydrogen ion secretion causes urinary acidification. The stones that are formed via this condition are composed of calcium phosphate. There are subclassifications of renal tubular acidosis that are beyond the scope of this article. Treatment is aimed at alkalization, most commonly potassium (either bicarbonate or citrate). Dietary support is - you guessed it - increased consumption of alkaline foods high in potassium (fruits and veggies) and limited consumption of acid foods.
- Bhandari A, Menon M. Reducing the risk of kidney stone recurrence. Patient Care, April 2004:26-32. www.patientcareonline.com.
G. Douglas Andersen, DC, DACBSP, CCN
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