Tryptophan is an essential amino acid most widely known as the compound in turkey that makes you feel sleepy. It’s a well-deserved association, but it’s also involved in other important metabolic processes. While the majority of consumed tryptophan is used for protein synthesis, a small portion serves as a precursor for the neurotransmitter serotonin and the hormone melatonin. Melatonin is responsible for sleep/wake signaling as part of your circadian rhythms, and serotonin helps regulate mood, appetite, and sleep. New research illustrates another important role for tryptophan and once again illustrates the complex interaction between your diet, your microbiome, and your long-term health and well-being.
The new study focused on the interplay between microglia and astrocyte cells. Microglia cells are basically the primary immune cells of the central nervous system. They act as macrophages that scavenge the central nervous system for dangerous plaques, damaged neurons, random cellular debris, and infectious invaders and then engulf them like white blood cells. They can also release various cytotoxic substances to kill invaders. Researchers from Brigham and Women’s Hospital discovered that these signals also activate an inflammatory pathway in astrocyte cells that damages neurons and leads to multiple sclerosis.
The researchers used knockout mice (mice that were genetically modified to turn off certain receptors) to see how certain metabolites of tryptophan released from the microbiome interacted with microglia cells. They found that certain compounds released from the metabolism of tryptophan were able to cross the blood brain barrier and activate a pathway that reduced inflammation and prevented multiple sclerosis. They studied brain samples from human multiple sclerosis patients and saw the same pathway in play. Other researchers found this pathway activation in Alzheimer’s disease, glioblastoma, and ALS (Lou Gehrig’s disease). The good news is that they view this as a positive step towards developing new therapies and treatment options for neurodegenerative diseases. The bad news is they currently don’t have probiotic or prebiotic recommendations to increase the release of these tryptophan metabolites.
Prebiotic tryptophan foods
Without specific microbiome recommendations from the researchers, your best bet is to follow best practices that improve microbiome health and diversity. Remember, the more variety of bacterial species in your microbiome, the healthier you are.
Tryptophan is primarily found in high-protein foods like meat, dairy, seeds and nuts. In general, vitamin B6 (pyridoxine) helps decrease the breakdown of tryptophan by the liver and increases uptake into the brain so it’s also good to focus on foods high in both. Good sources with both of these nutrients include turkey breast (of course), grass-fed beef, full-fat dairy, chicken breast, tuna, eggs, almonds, pumpkin seeds, sunflower seeds, peanuts, buckwheat, oats, chickpeas, bananas, and chocolate. Since the source of this neuroprotective effect comes from the metabolites released from your microbiome, you want to make sure you don’t just focus on meat and dairy. Foods like the nuts, seeds, and bananas may be lower in tryptophan and vitamin B6 than the meat sources, but they are much higher in beneficial prebiotic fiber which will improve the health and diversity of your microbiome.