What are Probiotics and How Can They Help Runners?


by Tara Postnikoff

Probiotics are the live “friendly” bacteria cultures that work to promote a healthy intestinal balance. The billions of bacteria living in your intestinal tract are often referred to as your microflora.

It is estimated that there are 10 times more bacteria in our body compared to the number of human cells. This can equate to up to 1.5 kilograms of weight in the gastrointestinal (GI) tract and there are up to 2000 different species of bacteria. These bacteria not only help with digesting food, manufacturing vitamins and regulating our immune system, they also have an impact on food cravings, mood and inflammation. Maintaining a balance of “friendly” bacteria versus harmful bacteria is critical for good overall health.

How can we maintain or improve our gut bacteria? Eating a healthy, balanced diet that is rich in vegetables, low in sugar and as minimally processed as possible will help give you a leg up on creating the best environment. The number of beneficial bacteria in your body may also be reduced due to stress, travelling, age, dietary changes, illness or lifestyle. Supplementing with probiotics can help re-establish or re-balance the gut ecology quickly, especially after a course of antibiotics or other medication. While probiotics may be added to food products, it is unknown how many beneficial bacteria are still alive at the time of consumption.

Most likely, the terms ‘gut bacteria’ and ‘probiotics’ prompt you to have thoughts about gut health and bowel movements. Maybe you’ve even heard that having ‘good gut ecology,’ meaning more good bacteria than bad, will strengthen your immune system. But emerging research is now showing that our gut bacteria has far greater reaches in our body than just the intestines and may also have an effect on our mental health.

The ‘brain-gut axis’ is a term being used to describe the interconnectedness of these two areas of the body. The intestine has its own nervous system and generates many of the same neurotransmitters that the brain generates. Your brain is able to send signals to your gut and your gut can talk to your brain through hormones stored in gut cells.1

 The foods you eat fuel you, as well as your bacteria. These foods will have a direct effect on the type of bacteria that takes charge in the gut, and will influence the messages that get sent to the brain. These include the “feed me” and “I’m full” hormones ghrelin and leptin, as well as the ‘feel-good’ or ‘stressed’ signals from neurotransmitters like serotonin, dopamine and tryptophan. Eating too much sugar-filled or processed food feeds the bad bacteria and you’ll likely crave more of those foods. If you eat a diet rich in plants, you’ll propagate more good bacteria and keep food cravings in check.

A 2007 study found that oral probiotics can affect neurotransmitters including tryptophan, serotonin, dopamine, acetylcholine and GABA, having a big impact on mood regulation.2Furthermore, we are seeing more clinical research from psychiatrists who are using probiotics in the treatment of anxiety and other mental health disorders. There is even favourable research to suggest that supplementing with probiotics has reduced the incidence of GI issues in athletes during events, reduced occurrence of infection and had a positive affect on performance when running in the heat.

A 2014 study in the European Journal of Applied Physiologyshowed that after four weeks of supplementation of 45 billion probiotic units daily, the run time to fatigue in the heat (35°C and 40% relative humidity) increased from 33 to nearly 39 minutes, a rise of 17 per cent.3Similar studies on triathletes in the Barcelona Challenge have shown decreased gut permeability and decreased race times in those that supplemented with probiotics.

Does this mean you should go out and start loading up on probiotics or foods containing probiotics? First, check your diet for unnecessary sugar or processed foods; reducing your consumption of those can help improve your gut flora. Next, consider consulting with a qualified health practitioner such as a nutritionist or naturopath, as they can help you decide what type of probiotic and dosage is best for you based on your needs and goals. For example, certain probiotic combinations have more effectiveness with antibiotics treatment whereas others are better for IBS management. Some products contain a pre-biotic known as FOS which provides food for the probiotic, some are better suited for kids, and still others are intended to support gastrointestinal health when travelling. For best results, look for a professional grade product that is kept in the refrigerator and consider a dosage of 10 to 25 billion units per day to get started. These should be consumed with food. Higher grade products will tell you both the type of bacteria (for example, Bifidobacterium bifidum) and the strain (for example, CUL-20). Consult the label and if necessary, ask the store staff for clarification before you buy. RR


Carabotti et al. The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems. Ann Gastroenterol2015, Apr-Jun; 28(2): 203–209.

  1. Cani and Delzenne. Gut microflora as a target
    for energy and metabolic homeostasis. Current
    Opinion in Clinical Nutrition and Metabolic Care
    2007, 10: 729–734.
  2. Shing et al. Effects of probiotics supplementation on gastrointestinal permeability, inflammation and exercise performance in the heat. Eur J Appl Physiol2014, Jan;114(1):93-103.


Tara Postnikoff is a Registered Nutritional Consultant, certified Personal Trainer and triathlon/running coach in Toronto. She is an avid distance runner and triathlete, and a regular guest speaker for Running Room training programs. To learn more, visit her website at www.heal-nutrition.com.

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