New research indicates that soybeans and soy-based foods may promote kidney stones in those prone to the condition, the American Chemical Society reports this week. US researchers at the Washington State University measured nearly a dozen varieties of soybeans for oxalate, a compound that can bind with calcium in the kidney to form kidney stones. They also tested 13 types of soy-based foods, finding enough oxalate in each to potentially cause problems for people with a history of kidney stones. According to lead researcher Dr. Linda Massey the amount of oxalate in the commercial products easily eclipsed the American Dietetic Association's 10 milligram-per-serving recommendation for patients with kidney stones, with some foods reaching up to 50 times higher than the suggested limit, she noted. Under these guidelines, no soybean or soy-[based] food tested could be recommended for consumption by patients with a personal history of kidney stones, she said. During their testing, the researchers found the highest oxalate levels in textured soy protein, which contains up to 638 milligrams of oxalate per 85-gram serving. Soy cheese had the lowest oxalate content, at 16 milligrams per serving. Spinach, measured during previous research, has approximately 543 milligrams per one-cup (2 oz. fresh) serving. According to Dr. Massey oxalate cannot be metabolised by the body and is excreted only through urine. The compound has no nutritional value, but binds to calcium to form a mass (kidney stones) that can block the urinary system, she added. Further research is needed to find types of soybeans with less oxalate, or to develop a processing method to remove the compound before it reaches consumers, she said. Full findings are published in the September issue of the Journal of Agricultural and Food Chemistry.