You’ve heard a lot about amino acids and how important they are to building muscle. But these building blocks of protein are responsible for many other critical systems and functions in the body, including hormone production, immune health, nervous system function, tissue repair, digestion and reproduction. They also function as neurotransmitters.
When you eat protein-rich foods, the body breaks them down into amino acids. Your body needs 20 different amino acids, categorized as essential, conditionally essential or nonessential.
Essential amino acids are considered so because your body can’t make them — you have to get them from your diet. The nine essential amino acids include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. Nonessential amino acids are synthesized by the body, even if they’re not consumed in the diet. The 11 nonessential amino acids include alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine and tyrosine. Conditionally essential amino acids, also called conditional amino acids, include some nonessential amino acids whose synthesis may be limited under certain conditions, including serious illness, injury, surgery or extreme trauma or stress. Tyrosine is considered an essential amino acid for people with phenylketonuria (PKU), a condition in which the body can’t synthesize tyrosine. Other conditional amino acids include arginine, cysteine, glutamine, glycine, ornithine, proline and serine.
You’ll find amino acids in a variety of foods, but there’s a catch: Meat, fish, dairy, eggs and other animal foods contain all nine essential amino acids and are considered complete proteins. Some plant foods — including soy and quinoa — contain all nine essential amino acids, but there’s some debate over whether they contain adequate quantities of each to be considered a complete protein. Beans, grains and nuts are also rich in certain amino acids but are low in or lacking others — called the limiting amino acid. For example, beans are low in methionine, and grains, nuts and seeds are lacking in lysine.
But if you eat a variety of plant-based proteins, it’s easy enough to compensate for limiting amino acids and get all nine essentials — and you don’t have to eat them at the same meal. Here’s a guide to the best sources of amino acids and ways to add them to your diet.
Grass-fed beef is a complete protein and has a superior nutritional profile compared with grain-fed beef, with less total fat and saturated fat and higher levels of omega-3 fats and antioxidants such as beta-carotene and vitamin E.
- Sauté thin strips of beef with broccoli, mushrooms, ginger, garlic, tamari and sesame seeds.
- Cook ground beef with crushed tomatoes, olives, capers, garlic, anchovies and red pepper flakes for a spicy puttanesca sauce.
- Simmer lean beef with barbecue sauce in a slow cooker, shred and serve on slider buns with coleslaw and pickles.
Tofu contains all nine essential amino acids, as well as calcium, iron and other nutrients. Edamame and tempeh are other good sources of protein and amino acids. Look for tofu made with calcium sulfate for the highest calcium content.
- Sauté tofu cubes with garlic, red pepper strips and green onions and toss with cooked rice noodles and sesame seeds.
- Crumble tofu, simmer in tomato sauce with onions, garlic and paprika and serve over brown rice.
- Toss edamame with quinoa, shredded red cabbage, carrots, red onions and cilantro and dress with a sesame oil vinaigrette.
Eggs are high in all nine essential amino acids, as well as other nutrients like choline, lutein and zeaxanthin. Look for pastured or true free-range eggs from chickens allowed to range freely outdoors and graze on grass, seeds and insects; some studies suggest they’re higher in omega-3s and significantly higher in vitamin D.
- Serve soft-poached eggs over sautéed escarole and radicchio and top with grated Asiago cheese.
- Halve boiled eggs and mash the yolks with avocado, shallots and green Tabasco sauce for spicy deviled eggs.
- Whisk eggs with almond flour, cheddar cheese and minced chives and cook in a waffle iron.
Buckwheat, in spite of the name, is gluten-free and technically not a cereal grain; it comes from a plant related to sorrel and rhubarb. It’s high in most essential amino acids and is also rich in polyphenols, fiber, magnesium and other nutrients.
- Toss buckwheat with shredded Brussels sprouts, hemp seeds, cherry tomatoes and chickpeas and dress with an olive oil vinaigrette.
- Top buckwheat with yogurt, frozen blackberries and chia seeds for an easy breakfast bowl.
- Toss buckwheat with roasted golden beets, red onions, arugula and olive oil.
Quinoa is rich in protein and contains all nine essential amino acids. It’s used as a grain but is actually a seed from a plant related to spinach and chard, so it’s naturally gluten-free. Quinoa is also high in fiber, potassium, iron and other nutrients.
- Grind quinoa into flour and use as a pancake base with blueberries, vanilla and honey.
- Toss quinoa with cherry tomatoes, shallots, basil, feta cheese and olive oil.
Hemp seeds are rich in protein and amino acids, as well as magnesium, zinc, iron and some B vitamins. They’re also an excellent source of omega-3 and omega-6 fatty acids. Combine them with beans or grains for a complete protein.
- Toss hemp seeds with black beans, corn, red peppers, cilantro and honey-lime vinaigrette.
- Top oatmeal with raspberries, hemp seeds and raw honey.
Cottage cheese, like other forms of dairy, contains all nine essential amino acids, as well as calcium, selenium, vitamin B12 and other B vitamins. Look for organic varieties, or try cultured cottage cheese, which is rich in probiotics.
- Mix cottage cheese with chia seeds, frozen berries and oats for a breakfast bowl.
- Add it to sautéed garlic, onions, frozen spinach and curry powder for a quick palak paneer.
Pistachios are actually the seeds from the fruit of the pistachio tree and contain a well-rounded array of essential amino acids. They’re also rich in potassium and monounsaturated fats, as well as lutein and zeaxanthin. Combine pistachios with beans or grains to form a complete protein.
- Add toasted pistachios, minced dried apricots, cardamom and cumin to brown rice for a Middle Eastern-inspired side.
- Grind pistachios into a meal and use as a coating for grilled chicken or fish.
Related: Fuel Up Your Fitness Routine
Amino Acids: What to Take
If you eat a well-balanced diet, you probably get sufficient amino acids in your diet. But for some people, supplementing with certain amino acids may be beneficial. Some to consider:
TRYPTOPHAN as a supplement may improve mood and help you sleep. In the body, tryptophan is converted into 5-HTP, which is used to make serotonin – a neurotransmitter that impacts mood, sleep and cognition – and melatonin, a hormone that’s involved in the sleep-wake cycle. Low serotonin levels have been linked to mood and sleep disturbances, and supplementing with tryptophan may enhance sleep quality and improve mood. In one study, people who consumed higher levels of tryptophan had significantly less depression, irritability and anxiety than when they consumed lower levels of tryptophan.
LYSINE inhibits the replication of the herpes simplex virus (HSV), shortening the normal course and duration of outbreaks and possibly lessening their frequency. HSV is dormant in the body until it’s triggered by stress or exacerbated by immune system dysfunction. It’s thought that the balance of lysine and arginine may impact the expression of the virus: The amino acid arginine is required for HSV to reproduce in the body, while lysine interferes with the absorption of arginine, making it less available. Lysine used topically, in ointments or salves, may also provide some protection; one study found an ointment that contains lysine, zinc and other herbs led to a full resolution of outbreaks by the third day in 40% of the study’s participants.
CYSTEINE plays an important role in immune health and scavenging free radicals that cause cellular damage; as a supplement, it’s usually taken in the form of N-acetyl cysteine (NAC), a stable form of cysteine. Studies show NAC elevates levels of glutathione, one of the body’s most important antioxidants, and may help protect against neurodegenerative diseases such as Alzheimer’s.
BCAAs, or branched-chain amino acids, are made up of three essential amino acids: leucine, valine and isoleucine. A number of studies suggest BCAAs can reduce soreness and lessen muscle damage and loss, though findings are mixed. And while further research is needed, BCAAs have been linked to promoting weight loss by reducing body fat, increasing lean muscle mass and preventing weight gain. Other research suggests BCAAs play an important role in immune system function, especially for athletes (we love the ultra-clean and high-quality BCAA powder from tattlewellness.com)