Post swim tummy bugs - does drinking cola really help? By Sarah Hill

In another in our series of open water swimming blogs, Manchester-based Total Immersion coach Sarah Hill uncovers the truth about the reported benefits of a post-swim Coke.

More people have discovered the joys of open water swimming this year than ever before, partly because of the amazing sunny weather but mainly because of the fact that lockdown restrictions have meant that we haven't been able to access pools.

Despite the variable water quality of our lakes and rivers, most swimmers will suffer no ill-effects but an unfortunate few will succumb to a post-swim upset stomach; a not uncommon problem for outdoor swimmers. 

There are a number of strategies you can  use to reduce your chances of getting a bug:

• Always check as best you can for up to date water quality information - see our previous blog post for great information on how to do this
• Avoid getting the water in your mouth as much as possible - this sounds obvious but it's not always easy on a choppy day - rinse out your mouth with clean water as soon as you can
• Always wash your hands well before eating or drinking after a swim - you can use some antibacterial gel if there's no clean water supply nearby
• Shower as soon as you can after your swim 

Many swimmers swear that drinking a can of Coke or other cola straight after a swim will prevent a tummy bug. The belief is that the phosphoric acid in the drink will neutralise any harmful bacteria but how much truth is there in this, does it really work or is more of a popular myth?

Unfortunately, there has been no proper scientific research done to either prove or disprove that cola works in this way. The research that has been carried out has been on a range of different foods testing their ability to fight bacteria, including virgin olive oil, vinegar, fruit juices, Coca-Cola, coffee, beer, and red and white wine. The vinegar and virgin olive oil showed the strongest bactericidal activity against all the bacteria tested; red and white wines also killed most strains but all the remaining drinks (including Coca Cola) had absolutely zero effect. The bug-killing capacity was put down to the high acidity of the vinegar, antioxidant compounds called phenolics in the virgin olive oil and the alcohol in the wine!

It is true that in its pure state, the phosphoric acid that supposedly gives cola its germ-killing properties is a strong acid with a PH of around 1 but the acidity of cola drinks that contain it is much weaker; far too weak to kill any bacteria. Bear in mind also that your stomach already contains strong hydrochloric acid whose job is to break down the protein you eat, killing any bugs along the way. This hydrochloric acid has a typical pH of around 1 making it far more acidic than any cola drink.

So, the reality is that there is no evidence available that backs up the belief that drinking Coke or any other cola drink after an open-water swim will reduce the likelihood of getting a tummy upset. Cola will give you a sugar boost so you may choose to drink it for a temporary post-swim energy boost but don't rely on it to keep the bugs at bay!