Drinking beer, wine or coffee can reduce the risk of kidney stone formation, according to a study from the USA. On the other hand, regular consumption of sugar-sweetened soft drinks increased the risk.

The study combined patients from the Health Professionals Follow-Up Study and the two Nurses Health studies (I and II) to amass a total of 194,095 participants. They were followed up by biennial questionnaire for a median of more than eight years, and assessed for their fluid intake and development of renal calculi.

Participants with previous stones were excluded from the study and this probably explains the relatively low incidence of stones, with only 4,462 cases during the follow-up period.

The main aim of the study was to investigate the association between different types of soft drinks (sugar-sweetened or artificially sweetened cola and non-cola) and kidney stone formation, but also to examine the effect of other drinks such as tea, coffee, wine, beer and orange juice.

The study used a reference group, for each type of drink, of those participants consuming less than one drink each month.

Drinks that increased the risk of stones:

• Sugar-sweetened non-cola soft drinks — 33% increased risk

• Sugar-sweetened cola drinks — 23% increased risk

• Artificially sweetened non-cola drinks — 17% increased risk

• Sugar-sweetened fruit drinks  — 18% increased risk

For artificially sweetened cola drinks there was a non-significant trend towards a decrease in risk.

Which drinks reduced the risk of stone formation? The results make encouraging reading.

Drinks that reduced the risk of stones:

• Beer — 41% reduced risk

• White wine — 33% reduced risk

• Red wine — 31% reduced risk

• Coffee — 26% reduced risk

Orange juice, decaffeinated coffee and tea showed small reductions of 12%, 16% and 11% respectively.

Anyone who has experienced the pain of renal colic will agree that prevention of kidney stones is a worthwhile pursuit.

For recurrent stone formers, the orthodox advice has always been that the most effective way to reduce the risk of further stones is to increase fluid intake, particularly avoiding dehydration at work, during sporting activity or on holiday when possible.

However, during this season of fluid excess, it is useful to know which drinks are best for reducing the risk of stone formation and subsequent colic.

This study has its limitations.

It was set in a population of health professionals, with a median age of 54, 51 and 37 in the three studies analysed. The population had low rates of obesity, with median BMIs of 25, 24 and 23 — hardly typical of the population as a whole, particularly in the USA.

Also, with the exclusion of previous stone formers from the study, it is hard to know how far these results are applicable to the recurrent stone forming group of patients — those who most often ask what they can do to reduce stone risk.

Consumption of sugar-sweetened drinks in particular increases the risk of stones, regardless of other disadvantages to health because of the calorie content.

This is another argument to encourage patients away from regular consumption of this type of drink. Artificially sweetened drinks appear better, if only for the lower risk of stones and lower calorie intake.

Dr Jonathan Rees