If it has anything to do with the gut, runners are typically already onto it. From how to move things through efficiently in time for an early race to what not to eat pre-, during and post- run, there’s not much this group won’t tackle when it comes to all things stomach related. Chances are, if you’re reading this, you’ve done your own fair share of gut research, and at some point asked yourself, “Should I or shouldn’t I?”

Probiotics, widely available on the market in several different forms, are strains of bacteria which are sometimes described as the good bacteria for the gut. It needs a healthy (individualized) balance of good and bad bacteria. When this is out of balance, this can be one of the factors that leads to poor gut health, striking with symptoms such as stomach cramps, bloating, gas and irregular bowel movements.

And while much of the focus for probiotics is always on gut health and helping runners stay regular, it turns out there may be a lot more behind the probiotics thing than just a good gut. Especially when it comes to endurance athletes, performance and staying immunologically healthy for the duration of the training season.

Focusing on Performance

For most athletes, at the root of any intervention, supplement or new training plan is the question, “How will it help my performance?” Coaches and researchers alike have recognized that probiotics may benefit athletic performance indirectly by maintaining optimized function in the GI tract and reducing the negative effects typically associated with exercise-induced immunosuppression.

Performance is enhanced when all systems of the body are functioning optimally. This includes mental concentration, mindset, physical capability, energy, immunity and the overall interaction of all of these systems of the body. That said, the research is strong to show the connection between the gut and brain, going so far as to support the existence of the gut brain axis. When the gut is optimized and functioning well, so too is the brain, and the mental performance level of an individual can be optimized. In the case of athletes, optimized mental performance leads to optimized physical performance.

Reducing Susceptibility to Illness

Improving performance is only half the battle however when it comes to endurance training. The other half is staying healthy enough while training at high volumes to be able to perform. Physical injury and getting sidelined due to vulnerable biomechanics and physiological stressors is always a burden in the back of an athlete’s mind. But so too is the need to avoid getting sick. Colds, flu, persistent fatigue, or overall wearing down due to the stress and demands of a high training load are also a thing to be worried about.

Running and endurance activities are a stressful activity to the body. When the body is under stress, it heightens immune response including activation of inflammation, and increase in the release of cytokines. Prolonged immunity activation means that the immune system becomes overworked, and when we need it—due to exposure to a cold or flu virus—it isn’t able to work at capacity and fend off the virus. This is why in periods of your training cycle which are particularly heavy, you may find yourself rundown with a cold, or a nagging illness that just won’t seem to go away.

But there is evidence to support that in male athletes, respiratory symptoms decrease with consumption of Lactobacillus, a bacteria strain found in many probiotics. In addition, probiotics have been shown to increase the ability for the immune system to enact pre-intervention immune response, i.e. increasing immune response before the illness takes over.

In contrast however, female athletes did not experience a decrease in respiratory symptoms to the same degree, and in some cases, instead had an increased symptomatic response. With the evidence available to support probiotic consumption in terms of both performance and immunity, it is apparent that they may have their place in an athlete’s regime, if nothing else, but for their ability to elicit indirect, but positive effects on an individual.

And while the yay or nay answer is different for every athlete, and can be altered depending on the type of probiotics you are going on and the number and type of available bacteria strains, it doesn’t really hurt to try them. And with the research behind to support the benefits towards decreased illness and fewer negative gut reactions, many of us would happily take a probiotic to avoid any unwanted mid-race pit stops. And an added performance boost is always a welcome bonus.