Kidney stone sufferers are often advised to increase their intake of fluids. While water is the ideal liquid, two studies show that the choice of other beverages may also be wise.
The first was a prospective study of 45,289 men with no history of kidney stones. After adjusting for age, dietary calcium, animal protein intake, diuretic use, geographic region, profession and total fluid intake, researchers found that each 8 ounces of beer lowered the risk of developing a kidney stone by 21 per cent, and each 8 ounce cup of decaffeinated or regular coffee reduced it by 10 per cent. Furthermore, each glass of wine reduced the risk of stones by 39 per cent. But the same amount of apple or grapefruit juice raised the risk by around 35 per cent (Am J Epidemiol, 1996; 143: 240-7).
Very similar but even more dramatic results were found in a study of the association between kidney stones in women and fluid intake (Ann Intern Med, 1998; 128: 534-40). Dr Gary Curhan, who oversaw both pieces of research, commented,"Alcohol suppresses a hormone that keeps the body from urinating, allowing for more frequent, more dilute urine." Caffeine has a similar effect, but Dr Curhan and his team were unable to explain why apple and grapefruit juices seem to increase the risk of stone formation.