Does Fermented Milk Increase Testosterone? An Evidence-Based Look

November 27, 2025 •

4 min read

According to a 2014 study on mice, consumption of the probiotic Lactobacillus reuteri found in some fermented milk products was shown to increase both testosterone levels and testicular size. This intriguing animal research has led many to question whether fermented milk can have a similar effect on human testosterone, a key male hormone.

Quick Summary

Exploring the complex relationship between fermented milk consumption and testosterone levels. Review the research on probiotics, gut health, and how they may indirectly influence male hormone production and balance.

Key Points

Indirect Effect: Fermented milk supports testosterone production primarily by promoting gut health and reducing inflammation, rather than providing a direct hormonal boost.
Animal Studies Show Promise: Animal studies, particularly with the probiotic Lactobacillus reuteri, have shown direct increases in testicular size and testosterone levels.
Reduced Inflammation is Key: Chronic inflammation, often linked to gut dysbiosis, can suppress testosterone. Probiotics in fermented milk help mitigate this.
Supports Overall Health: By aiding digestion, weight management, and nutrient absorption, fermented milk supports a bodily environment conducive to hormonal balance.
Combine with Healthy Lifestyle: For the best results, fermented milk should be part of a broader strategy that includes regular exercise, proper sleep, and a balanced diet rich in other hormone-supporting nutrients like zinc and magnesium.

Understanding the Gut-Hormone Connection

Testosterone is a vital androgen hormone, crucial for male fertility, libido, muscle mass, bone density, and overall well-being. While its levels naturally decline with age, factors like chronic inflammation, obesity, and poor diet can accelerate this process. This is where the emerging field of the gut-testis axis comes in. The trillions of microbes in your gut, collectively known as the microbiome, don't just affect digestion; they play a role in metabolism, immunity, and endocrine function. An imbalanced gut, or 'leaky gut', can lead to systemic inflammation that negatively impacts testicular function and suppresses testosterone production. Fermented milk products, rich in probiotics, are believed to support a healthy gut microbiome, which in turn can create a more favorable environment for hormone regulation.

The Evidence from Animal Studies

Research, particularly in animal models, provides some of the most compelling evidence for a link between specific probiotic strains and increased testosterone.

The Lactobacillus reuteri Study: A landmark 2014 study on aging mice found that those regularly consuming the probiotic Lactobacillus reuteri experienced significantly higher serum testosterone levels, larger testicle size, and increased spermatogenesis compared to control groups. The study's authors suggest this is due to the probiotic's anti-inflammatory properties, which counteracted age-related testicular atrophy.
High-Fat Diet Models: Other animal studies have shown that fermented milk or specific probiotic strains can mitigate the negative hormonal effects of a high-fat diet. Research in rats showed that kefir milk consumption decreased sperm alterations and preserved testicular histology, counteracting damage from a high-fat diet. Similarly, a study on diet-induced obese rats found that fermented milk with specific Lactobacillus strains helped maintain testosterone concentrations.

Insights from Human Research

While animal studies show promising direct effects, human research is more nuanced and primarily points to an indirect benefit through improved gut health.

Improved Fertility in Men: Some clinical trials on men with fertility issues have shown positive outcomes with probiotic supplementation. A 2017 study found that infertile men taking a specific probiotic/prebiotic blend saw improvements in sperm quality and testosterone levels. A similar 2022 clinical trial on men with idiopathic oligoasthenoteratospermia reported improved sperm concentration, motility, and sex hormone levels after probiotic supplementation.
Systemic Effects: The primary mechanism in humans is believed to be the modulation of the gut microbiome, which reduces systemic inflammation. By healing a 'leaky gut' and reducing inflammation, probiotics can remove one of the obstacles to optimal hormone production. This doesn't mean fermented milk will drastically boost testosterone in a healthy individual, but it can help maintain hormonal stability by supporting overall health.

Fermented Milk Products: What to Choose

For those interested in incorporating fermented milk into their diet, options like kefir and yogurt are popular choices. The nutritional profile and probiotic content can vary widely. When choosing, prioritize products with live, active cultures and minimal added sugar.


Comparison Table: Fermented vs. Unfermented Milk	Feature	Fermented Milk (e.g., Kefir, Yogurt)	Unfermented Milk	Implications for Testosterone
Probiotics	Contains high levels of beneficial bacteria and yeast.	Does not contain live, active cultures.	Supports a healthy gut, indirectly benefiting hormone balance.
Nutrients	Often richer in certain vitamins (e.g., B12) and minerals due to fermentation.	Standard nutrient profile, varies by fortification.	Vitamin B12 and D are linked to hormone production; enhanced absorption may be beneficial.
Absorption	Probiotics and gut health can improve the absorption of key nutrients.	Standard absorption rate.	Better absorption of nutrients like zinc and vitamin D can aid testosterone production.
Impact on Weight	Some strains may aid in weight management and reduce obesity-related inflammation.	Can be high in calories, depending on type (whole, low-fat).	Obesity is a major factor in low testosterone; managing weight indirectly helps hormone levels.
Inflammation	Anti-inflammatory properties through gut health improvement.	No specific anti-inflammatory effect.	Reduces chronic inflammation that suppresses testosterone.

Broader Lifestyle Factors

While fermented milk can be a valuable part of a hormone-friendly diet, it's not a magic bullet. For optimal testosterone levels, a holistic approach is essential. Consider the following:

Maintain a Healthy Weight: Obesity is a key contributor to low testosterone. A healthy diet, potentially including fermented milk, can support weight management.
Exercise Regularly: Resistance training and high-intensity interval training (HIIT) have been shown to increase testosterone levels.
Manage Stress: The stress hormone cortisol suppresses testosterone. Probiotics may help reduce cortisol, but overall stress management is crucial.
Prioritize Sleep: Poor sleep hygiene can disrupt hormonal cycles. Aim for 7-9 hours of quality sleep per night.
Balanced Diet: Ensure adequate intake of nutrients vital for testosterone production, such as zinc (oysters, red meat), magnesium (leafy greens, nuts), and healthy fats (avocados, olive oil).

Conclusion

Fermented milk, particularly varieties rich in specific probiotic strains like Lactobacillus reuteri, shows potential for supporting healthy testosterone levels. However, the evidence, especially in humans, suggests an indirect benefit. Fermented milk can help create a healthier internal environment by promoting gut health, reducing inflammation, and aiding in weight management. This, in turn, may support optimal hormone production. While it is not a direct, guaranteed testosterone booster, incorporating fermented milk into a balanced diet and healthy lifestyle is a sound strategy for supporting hormonal balance and overall well-being. Always consult a healthcare provider for any significant hormonal concerns.

An extensive review of the impact of gut microbiota and probiotics on male reproductive health, including testosterone production, is available from ScienceDirect. You can explore it further here: https://www.sciencedirect.com/science/article/pii/S1756464625002130.

Frequently Asked Questions

Kefir, a type of fermented milk, contains beneficial probiotic bacteria and yeasts that can support gut health. By improving your gut microbiome and reducing inflammation, kefir may indirectly support healthy testosterone levels.

Regular yogurt, especially varieties with live and active cultures, can support overall gut health. A healthy gut environment is linked to better hormone balance. While there is no direct evidence that yogurt significantly increases testosterone on its own, it can be part of a diet that supports it.

The gut-testis axis refers to the communication pathway between the gut microbiome and the testes. Imbalances in gut bacteria can cause inflammation that impairs testicular function and hormone production.

Kefir and yogurt are both good options. Look for products that contain live, active cultures and minimal added sugar. Some research points to specific Lactobacillus strains, so choosing a product with a diverse range of strains may offer more benefits.

While the process doesn't create testosterone, fermentation can increase the bioavailability of bioactive compounds and nutrients that are crucial for hormone synthesis. It can also reduce inflammatory factors that suppress hormone production.

Yes, fermented milk is generally considered better for hormonal balance due to its high probiotic content and potential anti-inflammatory effects. Unfermented milk lacks these live cultures.

Foods rich in zinc (oysters, beans), magnesium (spinach, almonds), and healthy fats (avocados, olive oil) are beneficial. Pomegranate and ginger have also been linked to positive hormonal effects in some studies.