What to Know About Essential Amino Acids

If you strip away the marketing and examine what the science actually says, the picture—as it often does!—becomes more nuanced. While branched-chain amino acid supplements can be helpful in specific circumstances, who needs them depends wholly on your individual circumstances. The good news, experts say, is it’s pretty straightforward.

What are branched-chain amino acids?

Like all 20 common amino acids, branched-chain amino acids (BCAAs) are building blocks your body uses to make protein. There are three branched-chain amino acids: leucine, isoleucine, and valine. These are essential and must come from the diet.

Their name comes from their chemical structure, which looks like a branch. Branched-chain aminos are largely metabolized in skeletal muscle, where they play crucial roles in building muscle, energy metabolism, and preventing muscle loss.

But they can’t work alone—they need help from other amino acids. Think of them like ingredients in recipes. You need the right mix of ingredients to make what you want. That’s why eating a variety of protein-rich foods—not just supplements—gives your body everything it needs to make the proteins that keep you healthy and strong.

When supplementation may make sense

There are some cases where BCAAs or essential amino acid supplementation can be beneficial.

• Older adults whose muscles have become less responsive to the things that normally help them grow, like eating protein and exercise
• Menopausal women
• People with liver cirrhosis
• Vegetarians and vegans
• People taking GLP-1 medications

Not everyone should take BCAAs. People with chronic kidney disease should avoid amino-acid supplements unless their clinician prescribes them, because protein and amino-acid intake must be individualized. People with metabolic disorders such as obesity, type 2 diabetes, and non-alcoholic fatty liver disease should avoid BCAA supplementation, as elevated circulating BCAA levels are associated with increased risk of insulin resistance, type 2 diabetes, and cardiovascular disease.

As always, check with your health care team before starting any new supplement. For those who decide supplementation makes sense, Adam Ross, a registered dietitian at the Atria Health Institute, recommends choosing an essential amino acid formula (which includes BCAAs) rather than BCAAs on their own. The key is to look for a serving that provides 2–3 g leucine (typically from 20–40 g of high-quality protein) to stimulate muscle protein synthesis. Older adults may benefit from at least 3g. While leucine is the spark, adequate total protein and essential amino acids, ideally around resistance exercise, do the building.

Third-party testing is crucial. Look for products certified by NSF Certified for Sport or United States Pharmacopeia (USP) Verified, which ensure you’re getting what the label says.

What are the nine essential amino acids?

Of the 20 amino acids, nine are considered essential because they cannot be produced by the body. It is essential that you get them through the food you eat. All three BCAAs are among the nine essential aminos.

What the essential amino acids do in the body

Muscle & metabolism: The branched-chain trio, leucine, isoleucine, and valine, concentrate in muscle. Leucine helps trigger muscle-protein synthesis (mTOR), while isoleucine and valine support energy use and repair.

Brain, mood & sleep: Histidine is a precursor to histamine, which helps regulate immunity, digestion, and sleep-wake cycles; it also supports healthy myelin. Tryptophan converts to serotonin and melatonin (mood, sleep) and can form niacin. Phenylalanine converts to tyrosine, feeding dopamine, epinephrine, and norepinephrine pathways.

Tissues, skin & connective support: Lysine and threonine aid collagen and elastin formation which is key for skin, tendons, and other connective tissues; lysine also supports immune function and calcium handling.

Detox & methylation: Methionine (a sulfur amino acid) supports methylation, antioxidant defenses (via cysteine/glutathione), and normal tissue growth; it also helps the body utilize selenium.

The bottom line is that a balanced diet that supplies all nine essential amino acids underpins muscle health, energy production, immunity, and brain function—no single amino acid can do it all.

What foods contain amino acids

Essential amino acids are found in many foods we normally eat. For most people, the best source of amino acids is dietary protein, especially animal proteins such as poultry, beef, fish, eggs, and dairy. These are easily absorbed by our bodies.

Foods like these that have all nine essential amino acids are called complete proteins. Most plant proteins are considered incomplete because they are low in one or more essential amino acids. The exceptions are soy and quinoa, which are both complete plant-based proteins.

By combining different plant-based foods, such as grains with legumes or beans with seeds, you can create a complete protein that supplies the full spectrum of essential amino acids. Combining plant proteins does not need to occur at the same meal, yet a variety should be consumed throughout the day.

Some example plant protein combinations include: rice and beans, hummus and pita, peanut butter toast on whole grain bread, and oatmeal topped with almonds, pumpkin seeds, or peanut butter.

The bottom line

Amino acids do more than just build muscle—they help build everything in your body.

For most people, just eating enough protein will give you all the amino acids you need. Aim for at least a half a gram of protein per pound you weigh (so if you weigh 150 pounds, eat around 75 grams of protein daily). Some experts, including Ross, suggest 0.7 grams per pound, and if you want to build muscle, eat a bit more. Get your protein from different foods and you’re set.

Additional resources

The foods below are high in amino acids

*Foods marked with an asterisk are plant-based complete proteins.

Histidine

Animal-based

Plant-based

Isoleucine

Animal-based

Plant-based

Leucine

Animal-based

Plant-based

Threonine

Animal-based

Plant-based

Tryptophan

Animal-based

Plant-based

Valine

Animal-based

Plant-based