Coffee, tea, beer, and wine seem to make kidney stones less likely.
METHODOLOGY: Researchers led by Dr. Pietro Manuel Ferraro at Catholic University of the Sacred Heart in Rome and Dr. Gary Curhan at Harvard reviewed data from 194,095 patients who had never before had kidney stones, for an average of eight years. The subjects all reported what they drank (on an annual or biennial basis), and how many stones they got.
The research did not involve ultrasounds or CT scans on all of those people to look for stones -- CT scans on 194,095 people would cause at least a few to get cancer -- so they only counted people who experienced symptoms from stones, like pain or blood in their urine. That means there were others who had secret stones that no one ever knew about.
RESULTS: Things associated with increased risk of kidney stones: Sugar-sweetened cola and non-cola drinks, artificially sweetened non-cola drinks (barely), and punch. Things associated with decreased risk of stones: caffeinated coffee (33 percent decreased risk), decaffeinated coffee (16 percent), tea (11 percent), red wine (31 percent), white wine (33 percent), beer (41 percent), and orange juice (12 percent). Apple juice and grapefruit juice showed no correlation.
Highlights of specific numbers: 205 out of every 100,000 people who rarely drank coffee got stones, compared to 137 out of every 100,000 people who drank it daily. 96 of every 100,000 people who drank red wine every day got stone stones, while 174 out of every 100,000 who drank it less than once a week got them.
IMPLICATIONS: People who get kidney stones have been traditionally told to drink "more fluids." This is a pretty massive study that narrows down that advice. Sugary soda seems to make things worse, but coffee, tea, beer, wine, and orange juice correlate with good. If it were a sugar issue, why would orange juice be better than soda? Fructose, which is high in both, has been associated with kidney stones, because it increases the amount of calcium in our urine. Obesity is also associated with stones, though, so it may be part of a bigger lifestyle picture. Also, orange juice has citrate, which is good for keeping stones away.
In summary, soda is not the best thing for our bodies. Diet soda is better but not perfect. Alcohol is a diuretic that flushes out our kidneys, which may be why this study saw "a reduced risk of stones in individuals who consumed higher amounts of wine and beer." For people who get urate kidney stones, which are an uncommon type, alcohol is still probably not a good idea, though this study made no distinction. Meanwhile for healthy people the healthiest diet seems to involve at least seven glasses of wine per week.