The brain is one of the most studied and mysterious parts of the body. It performs countless functions that are essential to survival—it is the coordinating center of sensations and intellectual and nervous activity. Our lifestyles have a profound impact on our brains; therefore, it is crucial to cultivate healthy habits. A well-fed brain is able to process information, remember, learn, focus, and maintain an active mind. The food we eat can greatly enhance the health and capabilities of our brains, especially as we age.
Inside the brain’s neurons, impulses are carried in the form of tiny electrochemical currents that involve a variety of substances called neurotransmitters. The most important neurotransmitters are dopamine, serotonin, and norepinephrine. These neurotransmitters belong to a class of chemicals called monoamines, which regulate our mood states and experiences of fear and pleasure. They also play key roles in many cognitive functions. A lack of balance among these neurotransmitters contributes to many psychiatric and neurological disorders, such as depression, schizophrenia, and Parkinson’s disease. Optimal eating for brain health depends on protein-rich foods full of brain-boosting nutrients called amino acids.
Amino Acids for Brain Function
Amino acids are the precursors of neurotransmitters, which is a sciency way of saying that amino acids make the neurotransmitters our brains depend on for balance and function. The amino acids tryptophan, tyrosine, and phenylalanine produce the neurotransmitters serotonin, dopamine, and norepinephrine. As proteins are composed of amino acids, and amino acids are the precursors of neurotransmitters, it is easy to see the connection between the food we eat and our brains. Alterations in the production of transmitters can directly influence the brain’s health.
Tryptophan is the rarest of the essential amino acids found in food and is the precursor of serotonin, one of the body’s natural antidepressants. Tryptophan can enhance positive mood and lower obsessive thinking, which is often related to eating disorders, anxiety, and depression. However, a careful balance is needed, because serotonin is an inhibitory neurotransmitter and an increase can induce the sensation of fatigue and ultimately sleep. It is a long-standing tradition to doze off after a big turkey dinner, and this can be attributed (at least in part!) to the relatively high abundance of tryptophan in turkey.
Tyrosine is the precursor of three neurotransmitters: norepinephrine, dopamine, and epinephrine. Tyrosine is not typically considered an essential amino acid because it can be synthesized by humans from phenylalanine; however, studies have shown that in certain instances the brain may not be able to synthesize sufficient tyrosine from phenylalanine to meet its needs. For example, delirium is associated with a low conversion rate of phenylalanine to tyrosine.
Tryptophan and tyrosine are the two primary amino acids connected to brain health, but there are other amino acids which play a role in brain function: acetyl l-carnitine (carnitine) and l-glutamine (glutamine). Carnitine converts fats in the body into fuel that can be used by the brain. This amino acid also removes toxins that interfere with brain activities. Glutamine improves the uptake of serotonin and dopamine, and stimulates the production of neurotransmitters that assist with brain function and focus. Glutamine can also be converted to the amino acid glutamate, another neurotransmitter.
BCAAs (branched-chain amino acids, leucine, valine and isoleucine) play an indirect role in the production of natural neurotransmitters. The BCAAs, along with phenylalanine, tyrosine, and serotonin, are all transported into the brain by the same transport system. An increase in BCAAs can inhibit the uptake of tryptophan, phenylalanine, and tyrosine by occupying the transporters.
The food you eat plays a key role in your brain health, and proteins supply your brain with the amino acids it needs to perform its daily activities.
Sources of Tryptophan
The best dietary sources of tryptophan are turkey and chicken. A 4-ounce portion of turkey or chicken breast provides 350 to 390 milligrams of tryptophan. Red meats also contain this amino acid, but they should be eaten in moderation because they have more saturated fat. Shrimp is also a good source of tryptophan; a 4-ounce serving contains 330 milligrams. Fish, such as tuna, halibut, salmon, sardines, cod, and scallops, contains between 250 and 400 milligrams of tryptophan per serving. Dairy contains less tryptophan per serving compared to meat and fish; a 1-cup serving of milk provides 100 milligrams of this amino acid. If you are vegetarian or vegan, keep in mind that among nuts, pumpkin seeds are the best sources because they provide 110 milligrams of tryptophan per one-fourth cup. Legumes, such as kidney beans and black beans, contain 180 milligrams of tryptophan per cup.
Sources of Tyrosine
Low tyrosine levels are rare, but you may need a higher dose during stressful times. Tyrosine is found in a variety of foods, such as meats and cheese. Roast beef, for example, has 1,178 milligrams per 3-ounce serving. Other meats such as pork chops, salmon, turkey, and chicken contain 900 to 1,000 milligrams per 3-ounce cooked portion. Parmesan cheese contains 559 milligrams per ounce, and one egg has 250 milligrams. Don’t eat meat? A cup of cooked white beans has 450 milligrams of tyrosine. The amount of tyrosine you need each day is linked to the essential amino acid precursor phenylalanine—for adults, that is 14 milligrams per kilogram per day.
Sources of Carnitine and Glutamine
Most animal-based foods are good sources of carnitine. Beef is one of the richest natural sources of carnitine. Lean cuts have 95 milligrams or less of cholesterol and fewer than 10 grams of total fat in every 3-ounce serving. Chicken breast is high in protein, low in fat and cholesterol, and a good source of vitamins and minerals. It also contains 3 to 5 milligrams of carnitine in every 4-ounce serving. All fish and shellfish have some carnitine (cod has the highest concentration of any seafood).
While your body normally makes all the glutamine it needs, a severe injury or illness may require you to increase your dietary intake. Meat, fish, and seafood are the best sources of glutamine. Many dairy products are also rich in glutamine, and whey protein, a byproduct of cheese production, is a top source of glutamine. Among animal products, eggs are also rich in glutamine. Dried lentils, peas, beans, and cabbage are excellent options for vegetarians and vegans. Many whole grains, including oats and products made from whole wheat, quinoa, millet, and brown rice, are also rich in glutamine.