These Are the 9 Essential Amino Acids Your Body Needs

Growing muscles, regenerating tissue, forming skin, hair, and bones—you have a lot of reasons to love amino acids. These molecules are the building blocks of protein. While your mind may automatically jump to muscle-building when you think of protein’s role in the body, both protein and amino acids play a larger role than that.

“Amino acids are important in your body, including [for] the synthesis of hormones, enzymes, and neurotransmitters,” says Lisa Young, RDN, an adjunct professor of nutrition at New York University and author of Finally Full, Finally Slim. They’re fundamental for growth, maintenance, and repair. Each type of amino acid serves a different or various functions.

“The body picks and chooses certain amino acids to build proteins, which in turn are used to form all kinds of things,” says Leigh-Anne Wooten, a registered dietitian nutritionist and founder of the nutrition consulting company Behind the Label. “When configured in different ways along with other ‘building blocks,’ if you will, they can form skin, hair, bones, tissues, organs, enzymes, hormones, and connective tissue, among other things,” she says.

(Related: 6 Antinutrients in Beans, Grains, and Veggies and How to Avoid Them)

What are essential amino acids?

There are 20 amino acids, including 11 our bodies can create. We get the remainder—what nutrition experts call the essential amino acids—from the food we eat. When a food has all nine essential amino acids it’s referred to as a complete protein. “A complete protein simply has all nine essential amino acids packaged in one food item, i.e. fish, chicken, or eggs,” says Wooten. Foods that contain some (but not all) essential amino acids are referred to as incomplete proteins.

Where do amino acids come from?

Essential amino acids can be found in foods high in protein, whether that’s animal- or plant-based protein. “The most typical and convenient sources of these amino acids are animal proteins like meat, eggs, poultry, and dairy products,” says John Troup, vice president of scientific affairs and dietary supplements at the Consumer Healthcare Products Association. Animal-based proteins are more easily digested and absorbed. Plus, they’re complete proteins.

Plant proteins contain amino acids, but many are incomplete proteins. (That’s the case with nuts, seeds, veggies, and whole grains.) There are a few plant sources of complete protein, including quinoa, soy, and hemp seeds.

Still, it’s possible for vegans, vegetarians, or individuals following plant-based diets to consume all the essential amino acids through food, explains Wooten. And you do that by eating a varied diet. You don’t have to eat all of the essential amino acids at one meal to reap the benefits. In fact, you don’t always have to eat complete proteins for your body to receive the important nutrients. “If you eat beans, which are an incomplete protein, but later eat veggies, that is OK,” says Young. “If you eat a varied diet, you should be able to get all essential amino acids over the course of the day.”

As long as you’re getting those nine essential amino acids, it doesn’t matter how you do it. “Eating a variety of plant-based, protein-rich whole foods will get you to the same endpoint: delivering all of the essential amino acids your body needs in order to do its thing [aka function properly],” says Wooten.

How the body uses amino acids

Each of the nine essential amino acids below serves different functions and roles in the body. “These proteins are important as they help the body grow and develop, repair body tissue, and help build skeletal muscle,” says Troup.

Histidine

“Histidine is used to make several hormones and is important for normal kidney [function], gastric secretion, and immune function,” says Wooten. “It’s also an important component of the myelin sheath, a protective barrier that surrounds nerve cells.”

Isoleucine

“Isoleucine assists in wound healing [and] cellular detoxification, supports the immune system, and promotes the healthy secretion of various hormones,” says Uma Naidoo, MD, a nutritional psychiatrist, professional chef, nutrition specialist, and the author of This is Your Brain on Food. “It is also important for regulating blood sugar and energy levels for fighting fatigue.” This amino acid is involved in immunity, protein and fat metabolism, and glucose transportation, according to Wooten.

Leucine

“Leucine supports protein synthesis and metabolic functions, including regulation of blood sugar levels, growth hormone production, and growth/repair of muscle and bone tissue,” says Dr. Naidoo. “It also helps prevent the breakdown of proteins in response to severe stress or trauma.”

Lysine

“Lysine supports protein synthesis, energy production, immune functions, and collagen formation, which promotes positive gut health,” says Dr. Naidoo. “It has also been shown to reduce overall cortisol levels to help with stress and anxiety.” Wooten says it also plays major roles in building proteins, hormones, and enzymes. Plus, it helps with the absorption of calcium.

Methionine

Dr. Naidoo points to methionine’s role in detoxification, tissue repair, and the protection of cells against pollutants and aging. “Methionine also plays an important role in fat metabolism,” says Wooten. “It also helps break down heavy metals in the liver, is used to build DNA, and acts as an antioxidant.”

Phenylalanine

“Phenylalanine is used to make neurotransmitters, the chemical messengers that deliver information between nerve cells,” says Wooten. Plus, this amino acid makes other enzymes that assist with creating other nonessential amino acids. “Because these molecules contribute to our stress response and feelings of pleasure, phenylalanine is considered to have potential therapeutic effects for anxiety and depression,” says Dr. Naidoo.

Threonine

Threonine plays a role in fat metabolism and immune function, says Wooten. “This amino acid is a structural aspect of various proteins that make up the skin and connective tissue, such as collagen and tooth enamel,” says Dr. Naidoo.

Tryptophan

You’ve probably heard this word get tossed around at the Thanksgiving table as family members discuss why turkey makes you sleepy. (It doesn’t, by the way.) “This amino acid aids in maintaining proper nitrogen balance and acts as a precursor to the neurotransmitter serotonin, which regulates mood, sleep, and appetite,” says Dr. Naidoo. You need this amino acid for general growth and development, as well as the production of niacin (vitamin B3), says Wooten.

Valine

Valine is important for stimulating muscle growth and regeneration, as well as energy production,” says Dr. Naidoo. “It can help fight fatigue, maintain mental vigor and emotional control, as well as strength muscle mass.”

(Related: 37 Secrets Nutritionists Won’t Tell You for Free)

Best food sources of essential amino acids

Whether you follow a specific diet or not, there are a variety of foods you can eat to get plenty of essential amino acids. “A vegan or someone on a plant-based diet can also get all 20 amino acids, including the nine essential ones—just not from one source,” says Wooten. Which is why we’ll remind you to eat a wide variety of foods. Sources of complete protein—that is, all nine essential amino acids—include:

• Poultry
• Fish
• Beef
• Eggs
• Pork
• Dairy
• Soy
• Quinoa
• Hemp seeds
• Chia seeds
• Pumpkin seeds

According to Dr. Naidoo and Wooten, the nine essential amino acids are also found in the following foods:

• Histidine: Beans, whole grains, certain whole wheat pastas, kamut, and teff
• Isoleucine: Lentils, nuts, seeds, beans, kamut, and teff
• Leucine: Beans and squash
• Lysine: Beans and peas
• Methionine: Beans, whole grains, Brazil nuts, and sesame seeds
• Phenylalanine: Beans, sunflower seeds, nuts, kamut, and teff
• Threonine: Flaxseeds, nuts, lentils, beans, green peas, and sweet potatoes
• Tryptophan: Oats, nuts, seeds, beans, and flaxseeds
• Valine: Peanuts, mushrooms, whole grains, beans, peas in pods, oats, and kamut

(Related: Is Quinoa Healthier Than Rice? Here’s What Experts Say)

What happens if you don’t get enough essential amino acids?

If you don’t get a sufficient amount of amino acids, your body may suffer. “A deficiency of amino acids may lead to decreased immunity, digestive problems, and slowed growth, particularly in kids,” says Young. According to Wooten, amino acid deficiency could manifest in any of the following ways:

• Loss of muscle mass
• Weakness
• Digestive problems
• Depression
• Fertility issues
• Decreased alertness
• Stunted growth (in children)
• Compromised immune function

“This wouldn’t happen overnight, but it could occur over an extended period of time without ingesting essential amino acids,” Wooten says.

Beware of too much protein

If you follow a plant-based diet, don’t worry about eating too much protein. “It’s hard to get too much protein from plant-based foods,” says Young. There are things to take into consideration if you eat animal meat, though. “Most Americans actually eat almost twice as much protein as they need each day,” says Wooten.

Overall, consuming too much protein isn’t an issue, but it also depends on the type of protein you’re eating. It’s not a good idea to eat lots of red meat, for instance, because it’s high in saturated fats.

So what happens to protein once it’s eaten? According to Wooten, once ingested, protein is used for one of four functions.

When there is just enough:

• Building muscles
• For other cellular needs (making hair, nails, skin, etc.)

When there is excess:

• Broken down and converted to fat or sugar to be stored (it then cannot be remade into protein)
• Excreted in your urine

“Unlike other nutrients [fat and carbohydrates] that can be stored in the body and called to action when needed, protein cannot be stored, so the [saying] ‘it just makes for expensive pee’ is true,” says Wooten.

What are “conditionally essential” amino acids?

“‘Conditionally essential’ means they play a more important role in times of stress or illness. These include arginine, cysteine, glutamine, tyrosine, glycine, ornithine, proline, and serine,” explains Troup. Conditionally essential amino acids can be produced by the body, but their production can be hindered when you’re under the weather.

“However, when the body is under stress/infection, the production is inhibited and it is important to get the conditionally essential amino acids from food,” says cardiologist Nieca Goldberg, MD, medical director of New York University’s Women’s Heart Program. “And discuss with their doctors if supplementation is needed.”

Kids’ bodies may not be able to process the amino acids like adults. “Often children also have not yet developed the metabolic ability to synthesize these amino acids in the same way that healthy adults can,” says Dr. Naidoo. “It is important to get enough of these nutrients through the diet as a means of preventing deficiency in case such conditions arise.”

Should you consider supplements?

One of the best ways to consume and receive the essential amino acids is through food. The majority of people, regardless of whether they are vegan or vegetarian, will not need to consider supplements to attain all the essential amino acids. “I do not recommend supplements,” says Young. “If you eat a healthy diet, you can certainly get them from the foods you eat. It’s also best not to take just one amino acid supplement without taking the others.”

But supplements may be a consideration in specific situations. “As a nutritional psychiatrist, I used to believe that getting all of our nutrients through the foods we eat is optimal,” says Dr. Naidoo. “While this remains true, I have discovered through my clinical work and research that we may sometimes need supplementation to help fill some nutritional gaps.” If you have concerns, speak to a medical professional about whether you’re getting sufficient protein and amino acids, or if you have a medical issue. “Speaking with your doctor and undergoing appropriate testing can help identify those who may or may not need supplementation,” Dr. Naidoo.

(Related: 15 Supplements Nutritionists Don’t Take—So You Shouldn’t Either)

How to calculate how much you need

Protein intake and needs will vary from person to person. “The recommended daily intakes are 0.8 grams per kilogram of body weight, but for active to very active lifestyles and in specific populations, such as the elderly, where muscle loss occurs at faster rates, protein intake should be optimized at 1.2 to 1.5 grams per kilogram of body weight,” says Troup. But, says Wooten, newer research suggests we might need a little more than that, closer to 1 to 1.4 grams per kilogram per day.

If you’re curious about how much protein you need per day, you can do a simple math calculation. According to Wooten: First, convert your weight to kilograms by dividing your weight in pounds by 2.2. So, a 150-pound person weighs 68 kg (150/2.2= 68 kg). If you’re aiming for a 1-gram-per-kilogram ratio, you have your answer: 68 grams of protein. To get the number for 1.4 grams per kilogram of body weight, take take the number in kilograms and multiply by 1.4 to get your range of protein for the day. So, a 68 kilogram person would need about 95 grams of protein per day (68*1.4 = 95).

How much do we need to get of each amino acid?

Dr. Goldberg states how much of each amino acid our body needs based on a person’s body weight:

• Phenylalanine: 33 mg/kg of body weight
• Valine: 24 mg/kg of body weight
• Threonine: 20 mg/kg of body weight
• Tryptophan: 5 mg/kg of body weight
• Methionine: 19 mg/kg of body weight
• Leucine: 42 mg/kg of body weight
• Isoleucine: 19 mg/kg of body weight
• Lysine: 38 mg/kg of body
• Histidine: 14 mg/kg of body weight

With so much information about protein and amino acids, it can be easy to feel overwhelmed and wonder if you’re receiving sufficient nutrients each day. It’s important to not overthink it or worry about each amino acid. Instead of scrutinizing everything you eat, opt for a varied diet.

“A balanced diet is important and should usually include 30 percent protein, 30 percent fat, and 40 percent carbohydrates of total calories consumed daily,” says Troup. “This adequately supports metabolic systems, muscle mass, and sufficient daily source of energy.”

Here is what Wooten recommends:

• Don’t stress about trying to get enough of a particular amino acid. Just focus on eating a variety of protein sources and you’ll be fine.
• Remember: protein is hiding in all kinds of plant-based whole foods.
• Include protein in every meal and snack.

Next, check out these high-protein plant-based meals.