You May Want to Rethink a Probiotic Supplement

Research weighs in on high doses of healthy bacteria before a run.


Every runner is familiar with GI distress. What runners may not realise is the intestinal tract is a key player in keeping pathogens out of your system and supporting a strong immune system. In order for it to do this, your GI tract needs healthy bacteria. But hard endurance training and elevated body temperatures from running can stress the gut by reducing blood flow to the intestines. After hard efforts, it’s possible for viruses and other pathogens to enter the gut, causing “leaky gut” (symptoms include diarrhoea and fever post-run).

But new research from Coventry University in the UK found that these negative effects may be mitigated with pre-run probiotics (healthy, good bacteria). To test this theory, researchers gave endurance athletes a probiotic drink with either L casei or a placebo for seven days prior to a two-hour run in the heat and humidity. They tested the levels of bacteria toxins (endotoxaemia) and inflammatory markers called cytokines (cytokinaemia) in the circulation pre and post heat run for up to 24 hours afterwards.

The results were surprising:  the probiotic dosing did not seem to offer protection and even led to a slightly higher level of endotoxaemia and cytokinaemia compared to the placebo drink.

How Probiotics Can Work For You

Eating food with live healthy bacteria, such as kefir, yoghurt and kimchi, has been shown to support intestinal health. But until more is known about what role probiotics supplements play in gut health, especially with regard to running in the heat, it may be best to stay away.


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