Protection against kidney stones with a low animal protein diet.




New England Journal of Medicine

Related Monographs

Consumer Data: Urinary Tract Infections (UTI)
Professional Data: Urinary Tract Infections (UTI)


Calcium is the most abundant mineral in the human body. Average healthy males have about two and a half to three pounds of calcium while females have about two pounds. Approximately 99 percent of calcium is present in the bones and teeth, which leaves only about one percent in cells and body fluids. While the most important function of calcium involves the maintenance of skeletal health, the small percentage of calcium outside the bones is used to maintain a variety of vital body functions.

When the body absorbs too much calcium, a condition called hypercalciuria occurs. The excess calcium is then passed through the urinary tract. As this happens, the elevated levels of calcium cause formation of calcium oxalate or calcium phosphate in the kidneys. This then produces kidney stones. Kidney stones are known to be extremely painful when having to pass through the urinary tract. Although men seem to be affected more than women, it is estimated that 10% of Americans will have kidney stones at some point in their life.1

Lifestyle options that can help prevent kidney stones are dietary changes. A recent study compared two different diets and the effects they had on reoccurring stones. This investigation included 120 men suffering from reoccurring stones due to hypercalciuria. Half of these men were designated to a diet of normal amounts of calcium, but lower intake of animal proteins and salt. For the rest of the men, the normal low calcium diet, usually suggested by health professionals, was assigned. After 5 years, 23 of the 60 men on the low calcium diet had a reoccurrence of kidney stones. As for the men on the low animal protein diet, only 12 out of the 60 had relapses. After a follow up, the levels of urinary oxalate had increased in the low calcium group, while decreasing in the low protein group. Urinary calcium levels declined in both groups by an average of 170 mg a day. The researchers concluded, " In men with recurrent calcium oxalate stones and hypercalciuria, restricted intake of animal protein and salt, combined with a normal calcium intake, provides greater protection than the traditional low-calcium diet."2


1. Institute of Diabetes and Digestive and Kidney Diseases, National Institute of Health. Kidney stones in adults. 2000.
2. Borghi L, et al. Comparison of Two Diets for the Prevention of Recurrent Stones in Idiopathic Hypercalciuria. NEJM. Jan 2002;346(2):77-84.