How tryptophan levels make a difference in your gut microbiome, help slow aging process

A recent study indicates that tryptophan, an amino acid, might be a key element in regulating the gut microbiome to protect against the adverse effects of aging. In return, a healthy gut microbiota allows for the production of serotonin, an essential neurotransmitter. Serotonin production then results in a lower risk of depression and longer stretches of nighttime sleep.

In previous studies, evidence shows that diet interacts directly with the bacterial microbiota of the gut in both human and animal models (particularly rodents). This new study development documents more of the symbiotic relationship between diet and gut health and the effects of overall well-being. 

“We think the microbiome plays an important role in the aging process and we think one of those players in the aging is tryptophan, which produces metabolites that affect every organ function […] We also have evidence that the composition of the bacteria that utilize tryptophan changes so even if you eat more tryptophan, you may not use it correctly,” explains Dr. Carlos M. Isales in a statement. Isales is the chief of the MCG Division of Endocrinology, Diabetes and Metabolism and a co-director of the MCG Center for Healthy Aging.

The Study Details and Results

Researchers use animal models to test how diets with varying levels of tryptophan, found in foods such as chicken, turkey, oats, and milk, affect the gut microbiome as an individual ages. ​​Over an 8-week time, researchers feed older mice three different tryptophan-centric diets (deficient levels, recommended levels, and high levels). 

In these short 8-weeks, unhealthy results occur inside the gut microbiome of mice when eating a diet low in tryptophan levels. One of these effects of a diet with low levels of tryptophan is that it results in lower levels of the bacterium, Clostridium. This bacteria is key in metabolizing essential amino acids, which results in the production of neurotransmitters like serotonin within the gut. Lower tryptophan levels also increase Acetatifactor bacteria levels to three times higher than normal. Acetatifactor is a bacterium that links to inflammation in the gastrointestinal tract.

A diet low in tryptophan affects the gut directly and indirectly within this study. Researchers find that low levels of tryptophan in the diet change the gut microbiota by reducing levels of Mucispirillum and Blautia bacterium. A low level of these two bacteria in the gut also links to gut inflammation that occurs in individuals with Crohn’s disease and colitis. 

However, when the older mice resumed a healthy and normal intake of tryptophan, some adverse gut microbiota changes reversed within a matter of days. Yet just increasing the level of tryptophan did not result in correcting adverse effects in all cases. Certain tryptophan metabolites can be damaging. This gives further indication that a better treatment is to give certain metabolites early on to keep the gut microbiota functioning at a healthy level rather than consuming a massive influx of tryptophan at once. Keeping the gut microbiota composition healthy shows to keep tryptophan uptake and usage in the body functioning optimally as well. 

Study researchers found that overall, low levels of tryptophan set the body up for system-wide inflammation

Future Benefits of the Study

Individuals are born with a certain type of gut microbiota that changes over time depending on diet, internal consumption, and environmental exposure. Many of these gut microbiota changes occur as individuals age, causing negative effects such as; lower brain function, metabolism, and inflammation. However, many researchers think that some of these adverse aging effects can diminish and reverse with the correct addition of essential diet elements that lead to healthier gut composition and body function.

“We accept as normal that your organs stop working as well. We accept that the ejection fraction of your heart drops as you get older. We accept that your brain function decreases as you get older. We accept as normal what is not normal,” says Isales.

Researchers think that certain parts of the aging process are unnatural, and healing to the gut microbiota can, in return, heal many of these negative outcomes. Adding further influence and tout to the idea of preserving a healthy gut microbiome can lead to longer and healthier lives.

This study is published in the International Journal of Molecular Sciences.

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