Can gut bacteria regulate testosterone levels and testicle size?

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The gut microbiota (the collection of all the microorganisms in your gut) has important roles in human health. Our microbiome has been implicated in regulating immunity, obesity, cancer and even behavior. Scientists are trying to understand the benefits of specific microbes and the mechanism of how these microorganism affect human health. While I was researching about our microbiome (the collective genome of all of our microbiota) I came across this interesting article entitled: “Probiotic Microbes Sustain Youthful Serum Testosterone Levels and Testicular Size in Aging Mice”

As males age, there is a reduction of circulating testosterone. This reduction of testosterone has many adverse effects including reduced sperm production, low sex drive, increased body fat, decreased muscle and bone mass, fatigue, testicle atrophy (balls shrinkage), and depression. In this study, the researchers showed that if they fed mice the probiotic bacteria Lactobacillus reuteri (a bacteria strain found in human milk and lives in our gut) it increased the size of their testicles and they also had higher levels of circulating testosterone compared to mice not fed Lactobacillus reuteri. In another experiments the researchers fed the mice a junk food diet but with the Lactobacillus reuteri, and still this group had bigger balls and more testosterone than the controls. The researchers propose that the probiotic bacteria increases gastrointestinal immunity. This increased immune response can activate metabolic pathways that restore tissue homeostasis and overall health.

Poutahidis et al. (2014) image source

While this research is done in mice, this research suggests that probiotic microorganisms may offer practical options for management of disorders frequently associated with normal human aging. Dietary L. reuteri or other probiotic supplementation may provide an alternative natural approach to prevention of low testosterone and male hypogonadism.

image source originally posted to Flickr as Operation: Truck Nuts - Successful Author: The359

So for a healthy body, you should get plenty of probiotic bacteria from living sources, such as fermented foods like:
Sauerkraut, Yogurt, Kefir, Cheeses, Pickles, and Kombucha. This will increase your overall health and testosterone production significantly.

Take care of your microbiome and your microbiome will take care of you.
Cheers!
ian

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References:
Poutahidis et al. (2014). Probiotic Microbes Sustain Youthful Serum Testosterone Levels and Testicular Size in Aging Mice. PLoS One. Jan 2;9(1) https://doi.org/10.1371/journal.pone.0084877