Explained: running, gut health, probiotics and performance

runner suffers stomach cramp

Running benefits the body in many wonderful ways, but it can also be a major gut stressor: anyone who’s had to cut a training session short or sprint to the portable loo in the middle of a run (or even earlier, which can be a terrible surprise) knows that running can cause gastrointestinal (GI) distress, especially for people with sensitive stomachs or chronic conditions such as irritable bowel syndrome. Experts say that material sloshing in the stomach (such as midrun fuel), decreased blood to the GI tract, and a weakened barrier between the intestines and the bloodstream (also known as ‘leaky gut’) can all be to blame. 

Related: 8 commandments of good running nutrition

What you put on your plate can do a lot to improve your gut microbiome (microorganisms such as bacteria in your digestive system). Research suggests that regularly consuming probiotics – the good bacteria that occur naturally in fermented foods – may strengthen the gut’s lining and lower inflammation throughout the body, resulting in less damage to your GI tract and fewer stomach problems during exercise. Those microscopic bugs (your gut has trillions of them) have also been linked to improvements in immunity, lung function and calcium absorption.

And in one 2014 study, athletes who took a probiotic supplement for four weeks worked out longer before fatiguing (37 minutes versus 33 minutes) than those who took a placebo. ‘My clients talk a lot about what they can’t eat because it upsets their stomach when they run,’ says Jessica Crandall, a spokesperson for the Academy of Nutrition and Dietetics. ‘It’s great to be able to add something to your diet that may benefit your gut, and your overall health and performance.’ But probiotics come in many forms, and they’re not all equal. Here are a few rules to maximise the benefits.

Opt first for real food

Probiotics occur naturally in fermented dairy products such as yoghurt, kefir and aged cheeses. They’re also found in other fermented foods and beverages, such as kimchi, sauerkraut, miso, kombucha and even sourdough bread. Today, you can find a wide range of foods – from baking mixes and cereals to ice cream and chocolate bars – that have been fortified with probiotics. You will, more than likely, pay more for them and many don’t have research to back up their claims. Plus, some preservatives and processing techniques (such as freezing and baking) can kill the delicate bacterial cultures, so those packaged goods may not even have any live probiotics to begin with, says Kristi King, clinical instructor at the Baylor College of Medicine, Texas, US.

Related: 10 foods to eat for a healthy gut

That being said, even dead probiotics may have health perks: in animal studies, for example, heat-killed probiotics have been shown to trigger immune-system responses. ‘Inactivated probiotics don’t give you all the benefits of live ones, but they still seem to be better than nothing,’ says Kantha Shelke, professor of food safety regulations at Johns Hopkins University, US, and a member of the Institute of Food Technologists. You can also look for products with the words Ganeden BC30 or Bacillus coagulans GBI-30,6086 on the label, says Shelke; they refer to a patented probiotic that’s been formulated to withstand microwaving, freezing, baking, and boiling.

Related: why your gut health is related to running success

For products that don’t require microwaving or freezing, look for labels with Lactobacillus or Bi dobacterium, two prominent probiotic strains. (Lactobacillus is sometimes abbreviated as L.) A 2017 literature review in the Annals of the National Institute of Hygiene found these strains to be the most beneficial for athletes’ health (and, possibly, performance). Foods with naturally occurring probiotics are your best sources.

Do you want to pop a pill?

Supplements may seem an easy way to boost your probiotic intake if you’re not getting enough through food. However, that’s not the full story. ‘Natural sources have the most beneficial bacteria from a digestibility and absorption standpoint,’ says Crandall. ‘Supplements aren’t closely regulated, and their cultures might not be active or easily absorbed for the gut to use.’ If you do opt for a supplement, pay attention to dosage. Studies on probiotics vary, but most have shown the greatest benefits at doses over one billion colony-forming units (CFUs) per serving, says Mary Miles, a gut microbiome researcher and professor at Montana State University, US. You also want a product that’s shelf-stable – as in, there is no refrigeration required – and that guarantees its potency until its expiration date. This helps ensure that the live cultures are still active and the most beneficial. (Most natural sources of probiotics aren’t labelled with CFUs, but foods such as yoghurt and sauerkraut can have higher concentrations per serving of the good bacteria than supplements do.)

Related: 4 reasons to eat more probiotics

Add probiotics slowly

Don’t wait until race weekend to eat a kilogramme of sauerkraut and kimchi, as appealing as that might sound. A 2015 review in the European Journal of Sports Science concluded that athletes prone to GI problems, or who are travelling to regions where GI problems are more likely to occur, may benefit from taking in some probiotics, but that they need to start taking them well ahead of competitions for best results. As Crandall says, ‘Then you can determine if there’s a difference in your training, your GI issues or your recovery after a long run.’