​Probiotics, Kefir, and Testosterone

Can Probiotic Supplementation Increase Testosterone Levels?

The Relationship Between Lactobacillus reuteri and Testosterone in Aging Men

There is growing recognition of the intricate connection between gut health and overall well-being, with increasing focus on how probiotics and fermented foods like kefir can influence hormone regulation, including testosterone levels. While gut health is linked to numerous bodily functions, the relationship between the microbiome, hormone production—specifically testosterone—and reproductive fitness, particularly in aging men, remains an area of emerging research.

Probiotics, such as Lactobacillus reuteri, have gained attention for their potential to support testosterone production by improving immune function and reducing inflammation. Research shows that supplementation with Lactobacillus reuteriATCC 6475 not only increases testicular weight but also enhances seminiferous tubule cross-sectional areas, promoting testosterone production. This probiotic may counteract age-related testicular atrophy and support healthier Leydig cells—the primary producers of testosterone in men (Poutahidis et al., 2014).

In their paper Probiotic Microbes Sustain Youthful Serum Testosterone Levels and Testicular Size in Aging Mice , researchers Theofilos Poutahidis, Alex Springer, and colleagues explore how probiotic supplementation—specifically with L. reuteri—can sustain testosterone levels and support testicular health in aging male mice. Their findings contribute to a deeper understanding of how gut health influences hormonal balance and reproductive fitness.

Through the lens of integrating fermented foods, including kefir, into the diet, this article explores the role of probiotics in supporting testosterone levels, which are vital for maintaining reproductive health, muscle mass, energy levels, and overall well-being in aging men.

The Broader Health Impact of Testosterone Decline in Men

Understanding the mechanisms behind age-related testosterone decline is not merely a matter of aesthetic or cultural concern. The consequences of reduced testosterone levels extend beyond societal perceptions of masculinity and youthfulness. Declining testosterone affects far more than physical appearance; it impacts reproductive health, mental acuity, immune function, and key markers of aging and longevity. Research suggests that Lactobacillus reuteri may play a crucial role in sustaining reproductive fitness and mitigating other adverse effects of aging, such as increased body fat, decreased muscle mass, and fatigue (Poutahidis et al., 2014).

Additionally, while the researchers only briefly touch on this, substantial evidence links testosterone levels to cardiovascular health. Low testosterone has been identified as a risk factor for cardiovascular disease, increasing the likelihood of myocardial infarction and stroke. In a large study, testosterone replacement therapy (TRT) was associated with a significant reduction in major adverse cardiovascular events (MACE), including death, myocardial infarction, and stroke, among men who achieved normalized testosterone levels. Specifically, men whose testosterone levels were restored to normal experienced a 26% lower risk of MACE and a 35% lower risk of all-cause mortality compared to those with persistently low levels. However, excessive testosterone supplementation—resulting in supraphysiological levels—was linked to an increased risk of stroke, underscoring the importance of careful monitoring (Anderson et al., 2016).

The Relationship Between Probiotics and Testosterone

Given the strong link between gut health and overall well-being, it is important to recognize the complex relationship between metabolic disorders, such as type 2 diabetes, and low testosterone levels.

Numerous studies have explored the association between type 2 diabetes, obesity, and reduced testosterone. Obesity, particularly when accompanied by insulin resistance, leads to a reduction in sex hormone-binding globulin (SHBG), which in turn lowers total testosterone levels. Severe obesity further suppresses free testosterone by disrupting the hypothalamic-pituitary-testicular (HPT) axis. In both metabolic disorders and aging, increased inflammation, pro-inflammatory cytokines, and insulin resistance compromise immune function, contributing to reduced testosterone levels.

The bidirectional relationship between obesity and testosterone creates a vicious cycle in which lower testosterone promotes further fat accumulation, exacerbating metabolic issues (Ng Tang Fui et al., 2014).

While investigating the effects of probiotic yogurt and purified lactic acid bacteria on obesity and cancer models, the authors of Probiotic Microbes Sustain Youthful Serum Testosterone Levels and Testicular Size in Aging Mice observed an unexpected outcome: male mice exhibited unusually large testes and increased social dominance behaviors. They found that supplementing aged mice with L. reuteri made them appear younger than their untreated counterparts, with treated mice displaying "luxuriant hair" and resistance to diet-induced obesity. The researchers also noted:

From an evolutionary perspective, we assert that lactic acid bacteria may have co-evolved with mammals exploiting testosterone to optimize mental, physical, and reproductive fitness. Higher serum testosterone levels compared to controls in our separate studies correlated with not only leaner physique but also increased muscle mass and higher activity levels in mice (data not shown). Benefits of this microbial synergy may extend beyond individual fitness to reproductive success, impacting a natural selection process favoring evolutionary success for the microbe and mammalian host (Poutahidis et al., 2014).

The researchers further observed improved wound healing and enhanced testicular health in L. reuteri-treated mice. Testicular weights in probiotic-fed mice were up to 25% higher than those in the control group, and serum testosterone levels were significantly elevated (Poutahidis et al., 2014).

The Relationship Between Inflammation, Immune Health, and Testosterone

Research shows that inflammation and immune health play critical roles in maintaining testosterone levels, particularly in aging men. As the immune system weakens and inflammation increases with age, testosterone production declines. Conversely, reducing inflammation and supporting immune function can help preserve healthy testosterone levels. The connection between gut health and testosterone production is becoming clearer. Studies in rodent models show that Lactobacillus reuteri reduces systemic inflammation by suppressing pro-inflammatory cytokines like IL-17, a key factor in age-related testosterone decline. This probiotic also enhances immune regulation by upregulating IL-10, improving testicular health and hormone production (Poutahidis et al., 2014).

A study published in BMC Microbiology, which characterized the anti-inflammatory properties of Lactobacillus reuteriBM36301, demonstrated its ability to reduce inflammation and enhance testosterone production. The study found that male mice supplemented with L. reuteri BM36301 showed significantly higher testosterone levels and improved testicular morphology compared to untreated mice.

The researchers noted:

Probiotics, such as L. reuteri BM36301, not only reduce systemic inflammation but also promote testosterone synthesis, likely through improved immune regulation and reduced oxidative stress (Park et al., 2016).

The study revealed that L. reuteri BM36301 promoted immune function by activating CD4+ regulatory T cells, which are crucial for controlling inflammation. Additionally, the probiotic reduced pro-inflammatory cytokine TNF-α, a contributor to testosterone suppression in aging males. Downregulation of cytokines such as IL-17, through IL-10's anti-inflammatory effects, further underscores the role of immune regulation in testosterone maintenance.

The study found a 25% increase in testosterone levels in mice treated with L. reuteri compared to the control group, suggesting that probiotic supplementation can counteract age-related testosterone decline through its anti-inflammatory properties (Park et al., 2016).

By addressing inflammation and supporting immune health, L. reuteri supplementation offers a promising pathway to improving reproductive health and mitigating the age-related decline in testosterone levels.

The Positive Influence of Kefir on Testosterone Production and Levels

As a natural source of probiotics, kefir has the potential to enhance gut health, which, in turn, can influence hormone regulation, including testosterone production. While the referenced studies focus on a purified strain of Lactobacillus reuteri rather than dietary sources like kefir, the presence of L. reuteri in kefir suggests that regular consumption could offer similar health benefits.

Probiotics, including those found in kefir, may improve immune function, reduce inflammation, and support the gut-brain axis, all of which contribute to balanced hormone levels. Although more research is needed to determine the exact influence of kefir on testosterone in humans, this probiotic-rich food shows promise as part of a dietary approach to supporting testosterone levels and overall reproductive health.

Summary of Research on Lactobacillus reuteri and Testosterone

Research demonstrates that supplementation with the probiotic strain Lactobacillus reuteri can significantly enhance immune health and reduce inflammation, both of which contribute to increased testosterone production. Key findings from the mouse model study include:

• L. reuteri supplementation increases testicular weight, even in mice on a high-fat diet.
• Testes from L. reuteri-treated mice show improved seminiferous tubule cross-sectional areas, indicating healthier tissue and potentially improved sperm quality.
• L. reuteri promotes more pronounced Leydig cell areas, which are responsible for testosterone production.
• Supplementation with L. reuteri elevates serum testosterone levels.
• Post-testicular sperm attributes improve with L. reuteri treatment.
• L. reuteri counters age-related testicular atrophy, supporting reproductive health in aging.

This research suggests that L. reuteri has the potential to support testosterone levels and reproductive health by improving immune function and reducing inflammation.

Key Insights on Probiotics, Testosterone, and Health

The far-reaching implications of low testosterone are profound, affecting not only reproductive health but also physical performance, mental well-being, and susceptibility to disease. This research underscores the potential of L. reuterisupplementation to support testosterone production through broader systemic benefits, such as enhancing immune health, improving tissue function, and reducing inflammation.

Additionally, research into other probiotic strains, such as Lactobacillus plantarum TWK10, reveals similar systemic advantages. In a study on mice, supplementation with L. plantarum TWK10 not only increased muscle mass but also improved exercise endurance and reduced fatigue-related biomarkers, including lactate and ammonia levels. These findings suggest that probiotics may play a key role in promoting both hormonal balance and physical performance. For those interested in the connection between probiotics, physical fitness, and aging, the study Lactobacillus plantarum TWK10 Supplementation Improves Exercise Performance and Increases Muscle Mass in Mice provides valuable insights.