Caffeine is Australia's favourite legal drug, and there are a lot of us who can't face the day without our morning cup of tea or coffee. Caffeine is an energy booster, an appetite suppressant, and most cafe staff will tell you that people are a lot nicer after their coffee, because it's a fantastic mood enhancer.
It's no surprise that various forms of this popular stimulant have found their way into supplements. Sometimes just listed in the ingredients as caffeine, or by its scientific name, 1,3,7-trimethylxanthine, ingredients like guarana, kola nut, and tea and coffee extracts are included in supplements for their caffeine content, and some form of caffeine appears in the majority of fat burners, weight loss proteins and pre-workouts.
Caffeine and Kidney Stones
Caffeine is generally regarded as safe by the TGA and other food and drug regulatory bodies, but with noticeable effects on the brain, nervous and cardiovascular systems and on the kidneys, many people have wondered whether caffeine is as harmless as they think. Thankfully, science is saying yes, and an American team has recently used data from a huge population study to show that caffeine seems to exert a preventative effect against kidney stones.
The Health Professionals Follow Up Study and Nurses' Health Studies (I and II) were large scale, long term health and lifestyle studies that have been very useful for looking at cause and effect across the population by virtue of their sizes – 217,883 people from the three studies were included in this analysis of caffeine and renal health.
The populations were divided into five groups, or quintiles, on the basis of caffeine intake, and the relative risks of kidney stones amongst each quintile were compared to the population that recorded no caffeine intake.
The results were quite profound, with the quintile representing the highest consumption of caffeine recording a 26-31% reduced incidence of kidney stones over the non-caffeine users. The researchers were able to analyse data from a smaller subset of these studies for whom the results of urine tests were available, and this provided some clues into the reasons for this result.
How do you get Kidney Stones?
Most urinary crystals are composed from a mineral called calcium oxalate, and are formed as a result of dehydration, or a low urinary output. These conditions make it more likely for minerals to precipitate out of solution. The results showed the heavy caffeine consumers had a reasonably high output of calcium, but that overall, their urinary output was copious, and dilute – conditions under which kidney stones are unlikely to form. Caffeine is a known diuretic, and it is extremely likely that this is the reason for the reduced incidence of kidney stones in high consumers.
It's very important to monitor your own health when you're taking any sort of dietary supplement, and users of pre-workouts and weight loss aids are encouraged to consult a doctor if they have any concerns. These are supplements that many healthy people use without negative side effects, and this latest research should give peace of mind to anyone with a history of kidney stones.
Ferraro PM, Taylor EN, Gambaro G, Curhan GC. Caffeine intake and the risk of kidney stones. Am J Clin Nutr. 2014 Dec;100(6):1596-1603.