Protein and Your Brain

When you eat protein, your body breaks it into amino acids. Some are used to make brain chemicals:

• Tryptophan, found in most protein foods, is used to make serotonin.
• Phenylalanine and tyrosine, also found in protein foods, are used to make dopamine and norepinephrine.
• Choline, found in eggs, fish, meat, and beans, is used to make acetylcholine. It is a nutrient, not an amino acid.

Your body needs a steady supply of these building blocks. They also need vitamins and minerals, such as vitamin B6 and iron, to work.

Several amino acids share one “doorway” to enter the brain, so they compete. What matters is the balance between them, not the amount of one alone. Carbohydrates, through insulin, can change that balance a little.

This is real physiology, but at ordinary meal sizes its effect on mood is small. It does not mean you can change your mood by eating one food.

Turkey is not unusually high in tryptophan, and tryptophan from a meal competes with other amino acids to enter the brain. Eating turkey is not a reliable way to raise brain serotonin or to feel sleepy. A large meal, and often alcohol, are the more likely reasons people feel drowsy afterward.

For most adults the recommended minimum to avoid deficiency (the RDA) is about 0.8 grams of protein per kilogram of body weight per day. That is about 54 grams for someone who weighs 68 kilograms, or 150 pounds. Some experts and newer guidelines suggest higher amounts for many adults, and needs can also be higher for older adults, during illness or pregnancy, and for some athletes, so ask your doctor or a dietitian about your own needs.

Protein foods include eggs, fish, poultry, lean meats, beans, lentils, tofu, yogurt and cheese, nuts, and seeds. Adding some protein to a meal also tends to keep blood sugar steadier and help you feel full.

In older adults, a 2021 review of studies found no clear link between how much protein people eat and their overall thinking skills. A possible link with memory showed up in a few studies, but those studies only looked at one point in time, so they cannot show cause and effect. The evidence is limited.

• Calvani, R., et al. (2021). Protein intake and cognitive function in older adults: A systematic review and meta-analysis.
• Columbia Mailman School of Public Health. Why does tryptophan in turkey make us sleepy?.
• Layunta, E., et al. (2021). Crosstalk between intestinal serotonergic system and pattern recognition receptors on the microbiota–gut–brain axis. Frontiers in Endocrinology, 12.
• Institute of Medicine (2005). Dietary Reference Intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids (protein RDA of 0.8 g/kg/day).