The good: Benefits of dairy for gut health
The bad: Potential adverse effects of dairy
The controversy: Conflicting research on dairy and gut health
Future directions in dairy and gut health research
Weighing the evidence
Did you know that your daily glass of milk could be shaping your gut microbiome in ways both beneficial and potentially harmful? With increasing research on the influence of diet on the gut microbiome, the debate over dairy’s impact on gut health has become more complex than ever.
Dairy consumption has long been a staple in human diets, providing essential nutrients such as calcium, protein, and probiotics. However, its effects on gut health remain a topic of scientific debate. While some studies highlight the benefits of dairy products in promoting a balanced gut microbiome, others suggest potential adverse effects, including lactose intolerance and inflammation.1
In this article, we critically examine the impact of dairy on gut health, outlining both the beneficial and detrimental effects, as well as the ongoing controversies in scientific research.
Image Credit: BearFotos/Shutterstock.com
The good: Benefits of dairy for gut health
Dairy products, including milk, yogurt, and kefir, play a significant role in promoting gut health through various mechanisms. Consumption of dairy products has been associated with an increase in beneficial bacterial genera such as Lactobacillus and Bifidobacterium.1
These probiotics are known to improve metabolic balance, modulate the immune system, and regulate inflammation. Components such as lactose and milk proteins, including casein and whey, serve as substrates that stimulate the growth of these beneficial bacteria. For instance, lactose possesses a prebiotic index similar to other known prebiotics, fostering the proliferation of beneficial gut bacteria.1
Certain dairy products have also been shown to suppress the growth of pathogenic bacteria. For example, yogurt consumption has been linked to a reduction in the abundance of Bacteroides fragilis, a pathogenic strain associated with gastrointestinal disturbances. This suppression contributes to a healthier gut microbiota composition, potentially reducing the risk of infections and inflammatory conditions.1
Milk also contains bioactive components such as casein, α-lactalbumin, β-lactoglobulin, and lactoferrin, which are known to protect the gut against various threats, including biological, chemical, mechanical, and immunological challenges, thereby maintaining the integrity and function of the gut barrier. A robust gut barrier is essential for preventing the invasion of dietary pathogens and toxins, which can cause severe intestinal inflammation.2
Furthermore, fermented dairy products like yogurt and kefir are rich in live active cultures that can colonize the gut, enhancing microbial diversity and stability. Regular consumption of these products has been associated with an increased abundance of beneficial bacteria and improved gut health.3,4 Research suggests that regular consumption of probiotic-rich dairy products may help balance gut microbiota, potentially reducing the risk of gastrointestinal diseases and metabolic disorders.5
Studies have also reported that lactic acid bacteria can enhance immune responses, improve gut barrier function, and contribute to the prevention of inflammatory bowel disease.3
Moreover, dairy-derived bioactive peptides and postbiotics may further support gut health. Fermented dairy products are also rich in postbiotics, which include beneficial enzymes and metabolites that can exert antioxidant, anti-inflammatory, and immunomodulatory effects.4
Another significant advantage of dairy is its contribution to gut integrity through calcium. Calcium is essential for maintaining tight junctions in the gut lining, reducing intestinal permeability, and preventing leaky gut syndrome.6
Furthermore, certain dairy products contain prebiotic components such as oligosaccharides, which serve as food for beneficial gut bacteria, further promoting microbial diversity and digestive health.7
The bad: Potential adverse effects of dairy
Despite its benefits, dairy consumption is not without potential drawbacks. Lactose intolerance, which is believed to affect approximately 65% of the global population, results from a deficiency in lactase, the enzyme required to digest lactose. The condition leads to symptoms such as bloating, diarrhea, and abdominal pain after dairy consumption.8
Additionally, dairy allergies, particularly to casein and whey proteins, can trigger immune responses ranging from mild gastrointestinal discomfort to severe allergic reactions. Dairy protein digestion also plays a role in gut health, with some individuals experiencing gastrointestinal discomfort due to inadequate protein breakdown and the formation of bioactive peptides that may influence gut motility.8
Emerging research suggests that dairy consumption may influence gut inflammation, although the findings remain inconclusive. Some studies indicate a potential link between high dairy intake and increased gut permeability, leading to systemic inflammation. However, other studies have indicated that there is no significant association between dairy intake and markers of gastrointestinal inflammation in healthy adults.9
Furthermore, certain dairy components, such as saturated fats and hormones in full-fat dairy, may contribute to inflammatory responses and metabolic disorders, though this remains a subject of ongoing investigation.10
The truth about milk: According to science | Prof. Tim Spector and Dr Sarah Berry
The controversy: Conflicting research on dairy and gut health
The scientific community remains divided regarding the long-term effects of dairy on gut microbiota. Some research indicates that dairy consumption can enhance beneficial bacterial populations, such as Lactobacillus and Bifidobacterium, which play a crucial role in maintaining gut health.1
Conversely, other studies suggest that dairy might negatively impact gut microbiota diversity, particularly in individuals with dairy sensitivities.5
The role of full-fat versus low-fat dairy products further complicates the debate. While full-fat dairy has been associated with higher microbial diversity and potential anti-inflammatory effects, some researchers argue that it may contribute to metabolic and cardiovascular issues when consumed in excess.11
Similarly, dairy processing methods and the presence of added sugars in flavored dairy products can also influence gut health outcomes. Additionally, the presence of antibiotics and hormones in conventionally produced dairy products has been a growing concern, as these factors may disrupt gut microbial balance and contribute to antibiotic resistance in the human microbiome.10
Moreover, the impact of dairy on conditions such as irritable bowel syndrome and Crohn’s disease also remains controversial. While some studies suggest that fermented dairy products may alleviate symptoms, others indicate that dairy elimination diets improve gut health in sensitive individuals.6
These conflicting findings indicate that more research is needed to determine the specific dairy components responsible for these effects and to understand how they interact with individual gut microbiomes.
Is The Carnivore Diet Healthy?
Future directions in dairy and gut health research
Given the complexity of dairy’s impact on gut health, future research needs to focus on personalized nutrition approaches that account for genetic, microbiome, and lifestyle factors. Advances in microbiome sequencing and metabolomics could help identify specific biomarkers that predict an individual’s response to dairy.
Additionally, long-term, randomized controlled trials comparing different types of dairy products — fermented versus non-fermented, full-fat versus low-fat, and conventional versus organic — could provide more definitive answers regarding the role of dairy products in gut health.
Another promising area of research involves the development of dairy alternatives that retain probiotic and prebiotic benefits while minimizing adverse effects.
Emerging technologies in food science, such as the fermentation of plant-based dairy substitutes with probiotic cultures, may offer new solutions for individuals with dairy sensitivities.
Weighing the evidence
Overall, the body of evidence indicates that the relationship between dairy and gut health is complex and highly individualized. While dairy can offer significant benefits through probiotics, calcium, and bioactive peptides, potential risks such as lactose intolerance, allergies, and gut inflammation should not be overlooked.
The available scientific evidence suggests that individuals with no intolerance or allergies can safely consume dairy, particularly fermented dairy products, to support gut health. However, those experiencing gastrointestinal discomfort may benefit from limiting or eliminating dairy and exploring plant-based alternatives.
Moreover, further research is needed to clarify the impact of dairy on gut microbiota and inflammatory responses, particularly through long-term, well-controlled human studies. Until then, personalized nutrition approaches should guide dairy consumption decisions, ensuring that dietary choices align with individual gut health needs.
References
- Aslam, H., Marx, W., Rocks, T., Loughman, A., Chandrasekaran, V., Ruusunen, A., Dawson, S. L., West, M., Mullarkey, E., Pasco, J. A., & Jacka, F. N. (2020). The effects of dairy and dairy derivatives on the gut microbiota: a systematic literature review. Gut Microbes, 12(1), 1799533. https://doi.org/10.1080/19490976.2020.1799533
- Wang, Y., Gong, Y., Farid, M. S., & Zhao, C. (2024). Milk: A Natural Guardian for the Gut Barrier. Journal of Agricultural and Food Chemistry, 72(15), 8285–8303. https://doi.org/10.1021/acs.jafc.3c06861
- Ağagündüz, D., Yılmaz, B., Şahin, T. Ö., Güneşliol, B. E., Ayten, Ş., Russo, P., Spano, G., Rocha, J. M., Bartkiene, E., & Özogul, F. (2021). Dairy Lactic Acid Bacteria and Their Potential Function in Dietetics: The Food-Gut-Health Axis. Foods, 10(12), 3099. https://doi.org/10.3390/foods10123099
- Okoniewski, A., Dobrzyńska, M., Kusyk, P., Dziedzic, K., Przysławski, J., & Drzymała-Czyż, S. (2023). The Role of Fermented Dairy Products on Gut Microbiota Composition. Fermentation, 9(3), 231. https://doi.org/10.3390/fermentation9030231
- Chen, E., Ajami, N. J., White, D. L., Liu, Y., Gurwara, S., Hoffman, K., Graham, D. Y., El-Serag, H. B., Petrosino, J. F., & Jiao, L. (2025). Dairy Consumption and the Colonic Mucosa-Associated Gut Microbiota in Humans-A Preliminary Investigation. Nutrients, 17(3), 567. https://doi.org/10.3390/nu17030567
- Thorning, T. K., Raben, A., Tholstrup, T., Soedamah-Muthu, S. S., Givens, I., & Astrup, A. (2016). Milk and dairy products: good or bad for human health? An assessment of the totality of scientific evidence. Food & Nutrition Research, 60, 32527. https://doi.org/10.3402/fnr.v60.32527
- Mondragon Portocarrero, A. D. C., Lopez-Santamarina, A., Lopez, P. R., Ortega, I. S. I., Duman, H., Karav, S., & Miranda, J. M. (2024). Substitutive Effects of Milk vs. Vegetable Milk on the Human Gut Microbiota and Implications for Human Health. Nutrients, 16(18), 3108. https://doi.org/10.3390/nu16183108
- Tagliamonte, S., Roberta, B. L., De Filippis, Francesca, Valentino, V., Ferracane, R., Guerville, M., Gandolfi, I., Barbara, G., Ercolini, D., & Vitaglione, P. (2023). Milk protein digestion and the gut microbiome influence gastrointestinal discomfort after cow milk consumption in healthy subjects. Food Research International, 170, 112953. https://doi.org/10.1016/j.foodres.2023.112953
- Bouzid, Y. Y., Chin, E. L., Spearman, S. S., Alkan, Z., Stephensen, C. B., & Lemay, D. G. (2023). No Associations between Dairy Intake and Markers of Gastrointestinal Inflammation in Healthy Adult Cohort. Nutrients, 15(16), 3504. https://doi.org/10.3390/nu15163504
- Malekinejad, H., & Rezabakhsh, A. (2015). Hormones in Dairy Foods and Their Impact on Public Health - A Narrative Review Article. Iranian Journal of Public Health, 44(6), 742–758.
- Schmidt, K. A., Cromer, G., Burhans, M. S., Kuzma, J. N., Hagman, D. K., Fernando, I., Murray, M., Utzschneider, K. M., Holte, S., Kraft, J., & Kratz, M. (2021). The impact of diets rich in low-fat or full-fat dairy on glucose tolerance and its determinants: a randomized controlled trial. The American Journal of Clinical Nutrition, 113(3), 534–547. https://doi.org/10.1093/ajcn/nqaa301
Further Reading