Johnson RJ, et al. - The increased intake of fructose, mainly as table sugar or high fructose corn syrup, in recent decades and its relation to increased risk for kidney stones allowed researchers to test the hypothesis that fructose might alter urinary constituents to favor calcium or uric acid stone formation. They examined 33 healthy male adults (40–65 years of age) participants of a previously published randomized controlled study. These subjects were given 200 g of fructose (supplied in a 2-L volume of 10% fructose in water) daily for 2 weeks and underwent assessments for changes in serum levels of magnesium, calcium, uric acid, phosphorus, vitamin D, and intact parathyroid hormone (PTH) levels as well as urine examinations. They noted that, by affecting urate metabolism and urinary pH as well as oxalate, fructose appeared to increase urinary stone formation to some extent. In subjects with metabolic syndrome and those suffering from heat stress, a possible contribution of fructose in kidney stone formation was suggested.