I am on a good news roll! How’s this for cheering? Scientists from the National Institute of Health have discovered that the nutrient taurine – which is an amino acid found naturally in our bodies and also in foods like meat and fish – helps our guts recall prior infections and to kill invading bacteria.[i] In our bodies, Taurine helps digest fats and thus, is found, as you can imagine, in bile acids. Research suggests that it may stimulate metabolism as well as have protective effects on the brain, heart and immune system. It’s important in the development of the nervous system and thus, a lack of taurine is associated with developmental disorders, as well as other illnesses like cardiomyopathy and atherosclerosis.[ii] There are animal studies showing it reduces glucose levels, improves insulin resistance, lowers cholesterol levels, alleviates neurotoxicity, improves memory and learning in an animal-model of Alzheimer’s.
The researchers transferred gut microbiota from mice that had previously experienced an infection (the food-borne pathogen Yersinia pseudotuberculosis) into germ-free mice whom they then exposed to the pathogenic bacterium, Klebsiella pneumoniae (Kpn). The gut microbiota helped prevent infection by the pathogen, and they were able to zero in on the particular class of bacteria that made the difference: Deltaproteobacteria. Guess what is the trigger for activating Deltaproteobacteria? Taurine. That is, animals who had been previously infected had higher levels of compounds containing taurine in their guts as well as higher levels of microbial species that consume taurine. And these bacteria can convert taurine into a molecule which impedes the growth of pathogens.
The paper’s authors believe that low levels of taurine in the gut allow pathogens to colonize. The metabolism of taurine leads to the production of a toxic gas called hydrogen sulfide. Adequately high levels of taurine produce enough hydrogen sulfide to prevent colonization. The researchers realized that a single, albeit mild, infection is enough to prepare the microbiota to resist subsequent infections and that supplementing mice with taurine also works to prepare the microbiota to battle infections in the future, increasing the level of hydrogen sulfide producing bacteria.
I found this very interesting as well: giving the mice bismuth subsalicylate (bismuth is the main ingredient in products like Pepto Bismol, which is commonly given to people for diarrhea, upset stomach) led to a decrease in the protection from infection because bismuth inhibits hydrogen sulfide production. Ugh oh – another vicious cycle is born: dysbiosis leads to unpleasant gut symptoms, so you take a medicine that further reduces your ability to fight pathogenic bacteria, which leads to worse dysbiosis, etc.
Hydrogen sulfide, with its distinctive rotten-egg smell, is actually incredibly toxic. A few breaths of air containing a high level of it can cause death. We produce small amounts of it, and it is a really important signaling molecule. For example, it relaxes the vascular system which is important in maintaining clean arteries. Evidence is mounting that it slows aging and is a regulator of lifespan, believe it or not. Levels of it tend to go down as we age, and this decrease is associated with potentially hypertension as well as cardiovascular disease, Parkinson’s and Alzheimer’s. “Data available so far strongly suggest that H2S may become the next potent agent for preventing and ameliorating the symptoms of aging and age-associated diseases…In the future, people may take H2S via food, or as an anti-aging supplement.”[iii]
Amazing, right? Hopefully, this information will lead to new treatments for gut bacterial infections in lieu of antibiotics.
[i] Stacy, A., et al. (2021) Infection trains the host for microbiota-enhanced resistance to pathogens. Cell. doi.org/10.1016/j.cell.2020.12.011.