It’s true that amino acids are the foundation of protein—one of the three macronutrients, along with fats and carbohydrates, that make up the bulk of the human diet. And yes, bodybuilders love aminos, since protein is critical for building muscle mass. There are a total of 20 amino acids that human bodies require to produce all the proteins needed to function and grow. Here’s what you need to know about them—including the benefits of the nine amino acids that are considered “essential.” While you need all 20 amino acids to function optimally, some of these are produced naturally by your body, making them nonessential amino acids. This means you don’t need to obtain them from the foods in your diet. Others are considered conditionally essential amino acids, meaning that they’re nonessential (i.e., your body produces them) except under specific circumstances, such as illness or stress. The nine essential amino acids, on the other hand, cannot be created by the body and must always be obtained from food. Although animal proteins such as beef, eggs, fish, dairy, and poultry contain good amounts of all nine essential amino acids (making them “complete” proteins), you can also obtain essential amino acids from plant-based foods. While it’s true that most plant foods don’t contain all nine essential amino acids (or at least not in adequate proportions), vegetarians and vegans can ensure healthy intake by consuming a variety of plant protein sources over the course of a day. You can search for foods that contain specific amino acids by using the USDA Food Composition Database. Here is more on each of the nine essential amino acids, including the main roles each one plays in the body and where to find them in your favorite foods: Histidine has antioxidant and anti-inflammatory properties and has been studied for its protective effects in chronic disease. It is also a precursor to the neurotransmitter histamine, which plays a vital role in immune functioning and helps produce red and white blood cells. Good food sources of histidine Animal-based: beef, lamb, pork, chicken, turkey, tuna, salmon, cheese, yogurt, milk, eggs Plant-based: tofu, soybeans, beans, lentils, pumpkin seeds, sunflower seeds, peanuts, quinoa, wild rice, brown rice, spirulina, wheat germ Isoleucine is also involved in blood clot formation and crucial for the production of hemoglobin, a protein in red blood cells that carries oxygen throughout the body. It helps regulate blood sugar and energy levels by increasing the body’s ability to utilize glucose2 during exercise. (Here’s how to tell if you have healthy blood sugar.) Good food sources of isoleucine Animal-based: beef, lamb, pork, poultry, tuna, seafood (tuna, cod, haddock), eggs, milk, yogurt, cheese Plant-based: soybeans, beans, lentils, oats, dried spirulina, seaweed, sunflower & sesame seeds Additionally, leucine helps produce growth hormones; prompts insulin release6, which plays a key role in regulating blood sugar levels and energy levels and helps promote the healing of muscle tissue, skin, and bones after trauma or severe stress. Good food sources of leucine Animal-based: cheese, beef, lamb, poultry, pork, tuna, shrimp, gelatin, collagen Plant-based: soybeans, beans, lentils, pumpkin seeds, sunflower seeds, pistachios, almonds, peanuts, spirulina, corn, wheat germ, quinoa, brown rice Lysine is also crucial for the production of collagen—the most abundant protein in the body that gives structure to ligaments, tendons, skin, hair, nails, cartilage, organs, bones, and more. Experts suggest that lysine, along with vitamin C and the amino acid proline, are essential for the formation of healthy collagen. Together, they form procollagen, which is then converted into several different types of collagen found in various tissues throughout the body. Lysine plays a role in mental health, too, with one study1 finding that supplementation of lysine, along with arginine, reduced anxiety and levels of the stress hormone cortisol. Good food sources of lysine Animal-based: beef, lamb, poultry, pork, tuna, shrimp, cheese, eggs, gelatin, collagen Plant-based: soybeans, pumpkin seeds, pistachios, lentils, beans, oats, wheat germ, quinoa, spirulina Along with offering internal protection, methionine helps to improve our appearance by enhancing the tone and elasticity of our skin and strengthening our hair and nails. Building upon its detoxifying properties, methionine also chelates heavy metals like lead and mercury and helps remove them from the body. It also acts as a lipotropic agent, helping to break down fat, and prevents fatty deposits in the liver. Too much methionine, however, may lead to atherosclerosis, or fatty deposits in the arteries. (Here are nine signs you need a detox.) Good food sources of methionine: Animal-based: beef, lamb, pork, poultry, tuna, salmon, shrimp, eggs, cheese, yogurt, milk Plant-based: Brazil nuts, soybeans, tofu, beans, lentils, quinoa, wheat germ, spirulina, peanuts One case study10 highlighted the importance of phenylalanine in Parkinson’s Disease because it helps to synthesize tyrosine, dopamine and norepinephrine - all of which are depleted in the disease. It has also been studied for its potential antidepressant properties11, although more research is needed. Good food sources of phenylalanine: Animal-based: beef, lamb, pork, poultry, cheese, tuna, salmon, eggs, milk, yogurt, gelatin, collagen Plant-based: soybeans, tofu, pumpkin seeds, peanuts, almonds, pistachios, cashews, quinoa, wild rice, brown rice, oats, wheat germ, spirulina Threonine is important for maintaining a healthy gut and digestive tract as well. It’s needed to produce the mucus layer that covers the digestive tract, and is important for protecting the integrity of the gut lining against stress14. Threonine (along with another amino acid serine), also plays an important role in T-cell functioning15 to optimize our immune systems. Additionally, threonine is important for fat metabolism and helps prevent fat buildup in the liver16. Good food sources of threonine Animal-based: beef, lamb, pork, poultry, salmon, tuna, shrimp, cheese, gelatin, collagen Plant-based: soybeans, tofu, pumpkin seeds, sunflower seeds, flaxseeds, peanuts, pistachios, cashews, almonds, beans, lentils, spirulina, wheat germ Research17 has found tryptophan to be effective at relieving symptoms of premenstrual syndrome, while low levels have been associated with mood swings, anxiety, and depression. This essential amino acid also supports the production of niacin (vitamin B3), which is involved in metabolism and helps convert macronutrients from the diet into energy for the body. Good food sources of tryptophan Animal-based: poultry, beef, lamb, pork, tuna, salmon, shrimp, cheese, eggs Plant-based: soybeans, tofu, beans, lentils, pumpkin seeds, chia seeds, pistachios, cashews, almonds, wheat germ, oats, spirulina Valine also has stimulant activity and has been said to help maintain mental and physical stamina19, while its role in the central nervous system supports emotional calm. Along with fellow branch chain amino acids, valine has also been shown to be a useful supplemental therapy in treating liver disease20. Good food sources of valine Animal-based: beef, lamb, pork, poultry, tuna, salmon, cheese, eggs, milk, yogurt, gelatin, collagen Plant-based: soybeans, mushrooms, pumpkin seeds, sunflower seeds, pistachios, cashews, wild rice, quinoa, brown rice, beans, lentils, oats, cooked broccoli, wheat germ, spirulina If not, then you may not be getting adequate levels of the nine essential amino acids. In that case, start eating more protein from a variety of plant and animal sources, like the ones mentioned above. If you’re a vegetarian or vegan, or anyone who’s not confident that your diet is quite cutting it in the protein department, consider supplementing with a quality protein powder, which can easily be added to smoothies, oatmeal, and baked goods. Whey protein is a naturally complete protein and contains an adequate proportion of each of the nine essential amino acids. Vegan protein powders are typically always complete, too, since they’re often made with a variety of different plant proteins (such as a combo of pea, hemp, and brown rice proteins) to cover all your bases, or they’re made from soy, one of the few complete plant-based proteins. If you choose a soy protein, just make sure it’s organic. Bottom line, though, is that you can definitely obtain healthy levels of all nine essential amino acids in a healthy, varied diet—regardless of whether that diet contains animal products. Yet, BCAAs may serve other purposes, too. Some experts tout their fatigue-fighting benefits, as research22 shows they can interfere with the transport of the relaxation-inducing amino acid tryptophan, thus preventing you from getting too sleepy. The good news: Unless your health care provider suggests otherwise, there’s no need to take a BCAA supplement if you’re eating well. After all, BCAAs are already found in the animal and plant foods listed in this article for leucine, isoleucine, and valine. Additionally, Hayim says that whey protein is one of the best sources of all three of these BCAAs.
