Fermented dairy products, microbiome and athletic performance

Fermented dairy products such as yogurt or kefir may play a more important role in endurance training than it seems.

A review published in Nutrients It analyzes its relationship with the gut microbiome and explores how that connection can influence immunity, recovery, and, indirectly, athletic performance.

This is not a clinical trial in triathletes, but a rigorous synthesis of the available evidence, so its conclusions should be interpreted in terms of potential and within the individual context of each athlete.

In recent years, intestine It has ceased to be "just digestion" and has become one of the most frequent conversations among endurance athletes, something we already analyzed in depth in our article on How the microbiota affects athletes.

It's not a fad, it's practical: when the digestive system fails, The training sessions are failingDiscomfort, inflammation, poor tolerance to certain foods, or a slower recovery often result in irregular weeks and less continuity.

What exactly does the study analyze?

With that starting point, a Spanish team led by Javier Modrego (INEF-UPM) has published a narrative review that collects and organizes the evidence on the axis dairy–microbiome–health.

The article reviews studies published between 2003 and July 31, 2025, with searches in PubMed, Web of Science and Google Scholar, following SANRA criteria for this type of review.

From yogurt to a healthy gut

The central message of the article is that milk, and especially the fermented dairy products (yogurt, kefir, skyr) can act as Functional FoodsThey not only provide protein, calcium, or vitamins, but also bioactive compounds and microorganisms capable of influencing the composition and function of the gut microbiome.

In simple terms, the review states that certain fermented foods are associated with a increase in bacteria considered beneficialas the Lactobacillus y Bifidobacterium, with a higher production of short-chain fatty acids (SCFAs) and with a tendency to reduction of pro-inflammatory markers in some contexts.

From there, a plausible chain of events emerges: less inflammation and better intestinal barrier integrity could promote more stable food tolerance, a more balanced immune response, and a more efficient metabolic environment.

And performance? An indirect relationship

It's important to be precise. The article mentions "physical performance" as a potential implication, linking it to mechanisms such as improved metabolic efficiency, reduced inflammation, better nutrient absorption, or fewer gastrointestinal symptoms that influence training.

However, it does not present a direct trial in triathletes that demonstrates a clear improvement in performance after introducing a specific fermented product.

The useful reading for the amateur triathlete is more realistic: if a food contributes to the the intestine is more stablebe less hassle and recovery will be more predictableThat can favor the constancyAnd in endurance sports, sustained consistency often makes the difference.

Lactose, tolerance and adverse reactions

The review devotes a significant section to the lactose tolerance and adverse food reactions. In fermented products, bacteria transform some of the lactose, which can make them more digestible for people with lactase deficiency.

It is also discussed how the composition of the microbiome itself can influence adaptation to lactose and the appearance of symptoms.

It is important to differentiate it from a milk protein allergywhich requires specific medical evaluation. The article mentions the microbiota as a possible modulator of tolerance, but does not present it as a universal solution.

Cardiometabolic health and the food “matrix”

Another important section addresses the relationship between dairy consumption and cardiometabolic markers. Recent literature emphasizes that the impact depends not only on fat content, but also on the food matrix and the kind of product.

In the case of fermented foods, mechanisms such as peptides with a possible effect on blood pressure (via ACE), changes in systemic inflammation, and microbiome-derived metabolites with influence on the gut-heart axis are cited.

These are associations supported by biological plausibility, not a closed recipe. But they reinforce an important idea for athletes: cardiometabolic health It is also built with sustained habits outside of training.

Along these lines, we have also addressed the relationship between diet and inflammation in Nutrition to control inflammation in athletes.

Emerging lines of research: exosomes and microRNAs

The article includes sections on exosomes y microRNA present in milk, encapsulated in vesicles that could partially resist digestion.

It is a growing field of research, with data from cell and animal models. However, the review itself acknowledges that in humans, the evidence remains limited. limited and inconsistentFor now, it's a promising line of research, but still far from clear practical applications.

How to integrate it into practice

If you tolerate dairy well, fermented foods can be a good option. An interesting option due to its nutritional profile and digestibilityNatural yogurt, kefir, or skyr fit easily into breakfasts, snacks, or as part of recovery, as long as they suit your preferences and individual response.

In cases of frequent gastrointestinal discomfort, the most prudent approach is to introduce them gradually and observe the response.

The amount, time of day, and type of product can make a difference. For persistent symptoms or suspected allergies, evaluation by a healthcare professional or a sports dietitian/nutritionist is the appropriate step, always within a comprehensive plan as explained in our [link to relevant articles/sections]. recommendations for nutritional planning for triathletes.

What the review makes clear

The article itself highlights a fundamental limitationDespite the volume of available studies, the overall results remain heterogeneous and, at times, contradictoryAs it is a narrative review, it does not offer a quantitative meta-analysis and groups together research with different designs, populations, and doses.

Therefore, any direct claim about improved performance would be simplistic. What it does clearly point to is the importance of integrate microbiome and nutrition within a broader strategy of health and sustainable training, especially in the context of personalization.

In triathlon, where consistency is everything, taking care of your gut environment may not give you immediate seconds, but it will help you sustain your effort over time.

Reference: Modrego J, Pantoja-Arévalo L, Gómez-Garre D, Gesteiro E, González-Gross M. Dairy-Gut Microbiome Interactions: Implications for Immunity, Adverse Reactions to Food, Physical Performance and Cardiometabolic Health—A Narrative Review. Nutrients. 2025;17(20):3312. DOI: 10.3390/nu17203312.