Tryptophan: A Very Essential Nutrient

If you’re interested in physical fitness, you’ve probably heard about amino acids. These nutrients are the building blocks of protein which helps to make your muscles strong. But amino acids are heavy lifters in many other parts of your body. They bolster your immune system and help to keep your digestion humming, among other benefits.

There are 20 different types of amino acids, all of which sustain your health. Nine are deemed “essential,” meaning they must be obtained through diet. Tryptophan belongs to this group and it is currently generating buzz in scientific circles.

A Mood-Boosting Nutrient

You’ve probably heard that your gut is your “second brain,” a concept fuelled by extensive research linking what you eat with how you feel. It’s common knowledge that consuming complex carbohydrates like whole grains and legumes helps to stabilize your mood. Now scientists are drilling down and identifying the pathways linking components of these foods with emotional well-being. Tryptophan is of interest because it jumpstarts activity on that biological superhighway known as the gut-brain axis.

Basically, tryptophan stimulates your body to produce serotonin. Known as “the happy hormone,” serotonin operates throughout your body, helping to keep you calm. Unsurprisingly, low blood levels of tryptophan are associated with anxiety, depression, behavioral disorders and even cognitive difficulties like memory loss.

Better Sleep

Tryptophan also affects how well you sleep. Your body fine-tunes the serotonin you produce to create melatonin. This hormone regulates sleep and wake cycles. Research shows that specific dietary techniques for boosting tryptophan raise melatonin levels, helping you to tap into the restorative power of a good night’s sleep.

Eat A Healthy Diet

High-protein foods are the best sources of tryptophan. These include eggs, poultry (turkey is well- known), whole grains, legumes, nuts and seeds. The blue-green algae spirulina is a particularly rich source of the nutrient.

Your Microbiome is Involved

Recently scientists have discovered a new pathway into how tryptophan works in your body: the bacteria that populate your digestive tract. Known as the gut microbiome, this bacterial ecosystem operates like a communications hub connecting your gut with your brain. Among their tasks, gut bacteria produce neurotransmitters — they manufacture about 90 percent of your body’s serotonin.  They also mediate how your body processes tryptophan.

Ideally, your gut is populated by diverse species of beneficial bacteria, a characteristic of a healthy microbiome. When your microbiome is in good shape it makes efficient use of the tryptophan you provide. But if it’s out of whack your body’s ability to process tryptophan may be compromised. Emerging research shows that certain species of bacteria are better at digesting tryptophan. If supplies of these helpful creatures fall short, it increases your likelihood of developing certain diseases.

This risk factor increases with age. Diet and lifestyle determine the types of bacteria that populate your gut. Unfortunately, behavioral changes associated with aging, including a more sedentary lifestyle and less nutritious diet (the “tea and toast” syndrome) play havoc with microbial ecology. To oversimplify, the older you are the less likely it is that your microbiota will be able to maximize the benefits of the tryptophan you consume.

Inflammation is a Risk

Following this breadcrumb trail leads to inflammation. Most of the chronic diseases associated with aging are linked with inflammation. This condition is so common in older people that experts have coined the term “inflammaging.”

Emerging research suggests that tryptophan may be helpful in controlling inflammaging. One study of elderly mice showed that 8 weeks on a low tryptophan diet sparked unhealthy changes in their gut bacteria. The quantity of a bacterium linked with intestinal inflammation tripled while that of a bacterium that metabolized tryptophan declined.

Another study looked at people with active celiac disease, which is characterized by intestinal inflammation. Celiacs are deficient in certain members of the lactobacillus family of bacteria, which are known for their ability to metabolize tryptophan. Researchers found that feeding mice a diet high in tryptophan increased the quantities of these helpful bacteria, protecting them from gluten-induced inflammation. We aren’t there yet, but the possibility of treating celiac disease with a combination of tryptophan and specific probiotics is looming on the horizon. 

Protein Plus

Most people obtain adequate tryptophan by eating a nutritious and balanced diet. The latest research suggests that nurturing a healthy microbiome should also come into play. We now know that eating an abundance of plant-based foods is the best way to build the bacterial diversity that will help your body utilize the tryptophan you provide. Obtaining tryptophan through high-protein, high-fiber whole foods like legumes and whole grains rather than supplements is the best approach. Foods contain many different substances, including gut-supportive prebiotics, that may work together, enhancing the effectiveness of the tryptophan you provide.

Judith Finlayson is the author of You Are What Your Grandparents Ate:  What You Need to Know About Nutrition, Experience, Epigenetics, and the Origins of Chronic Disease. Visit her at  

Selected Resources

Richard, D. et al. L-Tryptophan: Basic Metabolic Functions, Behavioral Research and Therapeutic Indications. International Journal of Tryptophan Research 2009.

Kaur, H. Tryptophan Metabolism by Gut Microbiome and Gut-Brain Axis: An in silico Analysis. Frontiers in Neuroscience 2019.

Yusufu, I. et al. A Tryptophan-Deficient Diet Induces Gut Microbiota Dysbiosis and Increases Systemic Inflammation in Aged Mice.

International Journal of Molecular Sciences 2021.

Lamas, B. et al Aryl hydrocarbon receptor ligand production by the gut microbiota is decreased in celiac disease leading to intestinal inflammation. Science Translational Medicine 2020.



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