Cola and hypokalaemia

Coca-cola gets a bad rap.

How many coke myths can you name?  You must have heard the one about coke being so acidic it can dissolve a steak (or tooth or penny)? What about “pouring coke on raw meat makes worms crawl out of it”? And, of course, there is the Mythbusters favourite: eating mentos with diet coke will make your stomach explode.

All bollocks, of course.

This week, the press have come up with a new one: drinking cola will damage your heart and cause paralysis.  This was variously reported as “Cola drinks can be bad for the heart” (Express); “Too much cola zaps muscle power” (BBC); and “Drinking large amounts of cola can cause paralysis, doctors warn” (Telegraph).

These reports are based on a study published recently in the International Journal of Clinical Practice, investigating a possible link between chronic cola consumption and hypokalaemia, a condition known to cause muscle weakness and an irregular heartbeat, amonst other things.  The study reviewed six case reports, featuring individuals who developed hypokalaemia following excessive cola consumption, including a middle-aged Australian farmer who would gulp back up to ten litres when out shooting kangaroos.

But let’s take a step back for a moment, and look at this skeptically:

  1. This is a small study, which examined only six individual cases occuring over the last fifteen years.
  2. There were no controls and no way to know if the individual patients involved had any other problems which could have accounted for their symptoms.
  3. There is no indication in the study as to how the authors quality-controlled the case reports they selected.
  4. The individuals featured in the study consumed between three and ten litres of cola per day, usually over the course of several years. That’s a lot of cola.
  5. If you’re consuming that much sugar, you’ve more reason to be worried about diabetes, obesity and tooth decay than the chance of developing hypokalaemia.
  6. Most importantly, of course: more research is needed.

Perhaps there is a real effect here – but it certainly isn’t case-closed and the press reports are needlessly alarmist.  At best, the study could be considered a pilot and used to solicit funds for a more rigorous and controlled investigation.  So there’s nothing to worry about yet, coke fans. Just remember to get plenty of exercise and enjoy coke in moderation. And remember to clean your teeth.

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