Are probiotics worth taking? A nutritionist's perspective

Probiotics are food supplements made up of live bacteria and yeasts that are beneficial to health, particularly to the digestive system. They are often referred to as “good” or “friendly” bacteria because they help maintain a healthy balance of microorganisms in the gut, supporting overall wellbeing.

These microorganisms are similar to the naturally occurring bacteria found in the human digestive tract and play a crucial role in digestion, nutrient absorption, and immune function.

What are the benefits of probiotics for athletes?

Probiotics have been recommended for a number of years now thanks to their positive effects on both the digestive and immune systems. They help restore the natural balance of gut bacteria, which can be disrupted by factors such as illness, antibiotic use, travel, or intense physical training like triathlon.

Maintaining this balance supports healthy digestion and may reduce the risk of gastrointestinal issues, which are common among endurance athletes.

Research suggests that the gut microbiota (the community of microorganisms living in the digestive tract) has effects reaching far beyond digestion. Evidence suggests that gut health can influence mood, stress levels, and sleep quality, all of which are essential components of recovery and performance (Gleeson, M., 2016).

Illustration of human intestines — Look after the health of your guts (Illustration by Daniel Seex)

For triathletes and other endurance athletes, recovery involves not only physical repair but also psychological restoration.

By supporting gut health, probiotics can help reduce the physical symptoms of stress, particularly during the post-race period when the immune system is most vulnerable.

They may also contribute to enhanced mood regulation and improved sleep quality. Together, these effects ensure that triathletes can recover more efficiently and return to training in an optimal state.

What type of probiotic supplement is best?

Can supplements interact with prescription medication?

The form of probiotic supplement can significantly influence its effectiveness. Evidence suggests that a water-based or liquid probiotic may be preferable to a tablet or capsule form.

This is because a tablet will be seen as solid food within the stomach and will be broken down by stomach acids before reaching the intestines, where probiotics exer their benefits, thus reducing the number of live bacteria that survive and reach the gut.

Whereas a liquid form will pass through the stomach directly into the gut where it can get to work immediately, colonising and begin benefitting the body. Liquid probiotics also often contain a wider variety of bacterial strains, which can support a broader range of gut functions and resilience.

When choosing a probiotic, athletes should look for strains that have been clinically researched for digestive and immune support—such as Lactobacillus acidophilus, Bifidobacterium bifidum, and Lactobacillus rhamnosus (Jager., 2019). Regular, consistent use is key to achieving and maintaining the desired effects.

What about natural sources of probiotics?

Greek yogurt in a glass jars with spoons,Healthy breakfast with Fresh greek yogurt, muesli and berries on background. — Credit : Getty Images

You can find natural probiotics (live microorganisms) naturally in certain fermented foods such as yogurt, kefir, sauerkraut, kimchi, miso, and kombucha. These foods have been consumed for centuries and are among the most accessible sources of beneficial bacteria, including strains of Lactobacillus and Bifidobacterium.

Whether natural probiotics are better sources than supplements depends on individual needs and circumstance. For most healthy individuals, regularly consuming fermented foods can be sufficient to support gut health (if you like the taste, of course). However, supplements offer a more concentrated and controlled dose of specific probiotic strains that have been clinically tested for targeted benefits, which is something real foods can’t always guarantee.

For more nutrition tips, check out our article on the most important nutrients for keeping your immune system healthy.

About

Renee McGregor (BSc (hons) PGDIP (DIET) PGCERT(sportsnutr) RD BASES) is a leading sports dietitian, specialising in eating disorders, REDs, The Female Athlete, athlete health and performance. Her practice and knowledge is supported by extensive experience of working in both clinical and performance nutrition, including Olympic (London, 2012), Paralympic (Rio, 2016) and Commonwealth (Queensland, 2018) teams. She is presently working with a number of national governing bodies, including Scottish Gymnastics, The GB 24 hour Running squad, Scottish Ballet, Women’s Reading Football and England National Ballet. She has also provided CPD to The Welsh Institute of Sport and Sports Institute, Northern Ireland. On top of this Renee is the diet lead for global ultra-marathon events series Ultra X, part of the Stylist Strong Women series and an ambassador for Bath MIND Charity. She is regularly asked to work directly with high performing and professional athletes that have developed a dysfunctional relationship with food that's impacting their performance, health and career. No matter who she is working with, whether that’s elite, club-level athletes or those with a dysfunctional relationship with food and training, compassion and care is always central to her practice. She provides a person-centred, holistic approach. She's the best-selling author of Training Food, Fast Fuel books. and Orthorexia, When Healthy Eating Goes Bad. She is the co-founder and director of #TRAINBRAVE a campaign raising the awareness of eating disorders in sport; providing resources and practical strategies to reduce the prevalence. In 2020, in order to increase accessibility to her knowledge and experience she started The Trainbrave Podcast and had over 40,000 downloads in its first year. She is on the REDS advisory board for BASES (The British Association of Sport and Exercise Science) and sits on the International Task Force for Orthorexia. Renee has been invited to speak at several high profile events including The European Eating Disorder Society Annual Conference as the UK expert in Orthorexia, Cheltenham Literature Festival, Cheltenham Science Festival, The Stylist Show and Google. She writes for many national publications and is often asked to comment in the national press. She regularly contributes to radio and TV, including News night and BBC 5 Live. On top of this Renee recently appeared on BBC to support as a diet lead in Freddie Flintoff’s ‘Living with Bulimia’ documentary.