Everyone knows that a healthy diet requires protein. But proteins are made up of smaller units called amino acids that occur naturally both in the human body and the food we eat, and they’re critical to your body’s most important functions.
Your body gets its amino acids from breaking down proteins. There are many types of amino acids with different functions, all of which are required for healthy growth and development. Because our bodies depend so heavily on them, it is important that we understand just what are essential amino acids and what do they do in our bodies.
What Is an Essential Amino Acid?
The most important category of amino acids are the essential amino acids, because these are the ones that your body cannot produce on its own. You have to get them from the food you eat.
What Is a Nonessential Amino Acid?
Nonessential amino acids are those that your body already produces naturally. Contrary to what their name might suggest, nonessential amino acids are quite important too — they’re also critical for our overall health and wellness.
What Are Conditional Amino Acids?
Finally, there is a third category of amino acids described as conditional, because they are only essential under certain conditions. While conditional amino acids do occur naturally in your body, they cannot be synthesized in sufficient quantities during certain physiological states like pregnancy, adolescent growth and recovery from trauma.
At these times you must consume increased amounts of these specific amino acids, which makes them conditionally essential. The conditional amino acids include arginine, cysteine, glutamine, glycine, proline and tyrosine.
What Do Amino Acids Do?
Amino acids are in fact the building blocks of proteins, which are just long chains of amino acids. The specific combinations determine how the protein functions in your body, similar to using different ingredients to make different recipes.
Various proteins are responsible for processes such as growing and repairing body tissues, breaking down and digesting food, regulating hormones and neurotransmitters, providing a source of energy, maintaining healthy hair, skin and nails, building muscle and even boosting your immune system.
Amino acids also function as the backbone of compounds like hormones and neurotransmitters. Neurotransmitters are chemical messengers that carry signals between nerves, muscles and cells. These messengers are at work when you move your limbs or just feel a sensation in your body. They even keep your heart beating.
How Many Essential Amino Acids Are There?
There are hundreds of amino acids that occur in nature, but only 20 are needed for the human body to function. Of these 20, only nine are considered essential.
What Are the Essential Amino Acids?
The nine essential amino acids, those that are not produced by your body, are listed below.
Phenylalanine is necessary for the production of neurotransmitters such as dopamine, epinephrine and norepinephrine. It also plays an integral role in the biosynthesis and production of other amino acids. Phenylalanine is found in soy, nuts, beans and even the sugar substitute aspartame.
Valine stimulates muscle growth and tissue regeneration and is used in energy production. It also helps us maintain mental vigor and emotional calm. Valine is found in soy, peanuts and vegetables like mushrooms.
Threonine is a principal component of proteins like collagen and elastin, which provide structure to skin and connective tissue. It can help form blood clots, which prevent excessive bleeding. Threonine also plays an important role in immune function and can prevent fat buildup in the liver. Threonine is found in wheat germ, lentils and sesame seeds.
Tryptophan helps make the neurotransmitter serotonin, which regulates your appetite, sleep, pain and mood. It also helps maintain the nitrogen balance of your body. It is a natural sedative and commonly associated with drowsiness. Tryptophan is found in brown rice and soybeans.
Methionine is essential for metabolism and detoxification and helps your body absorb vital minerals like zinc and selenium. It is also required for tissue growth and repair. Methionine is found in sesame seeds, brazil nuts and cereal grains.
Leucine is another amino acid that is essential for muscle tissue growth and repair, and helps to stimulate wound healing. Leucine also helps the body make growth hormones and regulate blood sugar levels. Leucine is very widely available in food — including soy, nuts, brown rice, legumes like lentils, beans and oats.
Isoleucine is heavily concentrated in your muscle tissue and plays a role in immune function, regulating energy and creation of hemoglobin. It also promotes muscle metabolism and recovery. Isoleucine is found in lentils, nuts and seeds.
Lysine has a wide range of functions and is important in the production of energy, hormones, enzymes, collagen and elastin. It also plays a major role in immune function, calcium absorption and protein synthesis. Lysine is found in soy, black beans, quinoa and pumpkin seeds.
Histidine, when metabolized, is responsible for the neurotransmitter histamine, which is crucial for immune response, digestion, sleep cycles and sexual function. Histidine also helps create blood cells and maintains myelin sheaths, which protect your nerve cells. Histidine can be found in nuts, seeds and whole grains.
What Are the Effects of Amino Acid Deficiency?
Amino acids play an important role in many bodily components and processes, and if you don’t have enough of these amino acids in your body, you could develop symptoms that include (but are not limited to) general weakness, digestive upset, decreased immunity, fertility issues, decreased muscle growth in adults and stunted growth in children as well as increased depression and anxiety, decreased mental alertness and fatigue.
The good news is that although we all need to get enough protein, if you are otherwise healthy and eating a moderately varied diet that provides enough calories overall, you are unlikely to experience an amino acid deficiency.
Some of the specific deficiencies associated with each essential amino acid are as follows:
- Phenylalanine: poor weight gain in infants, eczema, fatigue, memory problems
- Valine: insomnia, reduced mental function
- Threonine: muscle loss, memory loss, weakness, fatigue
- Tryptophan: skin rashes, digestive upset, even dementia
- Methionine: hair loss, liver dysfunction, raised toxicity levels
- Leucine: hair loss, skin rashes
- Isoleucine: muscle wasting, shaking
- Lysine: nausea, stunted growth, hair loss
- Histidine: reduced hemoglobin, anemia
What Is The Recommended Daily Allowance of Amino Acids?
Like most nutrients, a person’s optimal consumption of nonessential and essential amino acids is dependent on their physiological state and may differ between individuals. Amino acids that are consumed in excess of what your body requires are degraded and either excreted through urine or stored as fat or carbohydrates.
Essential amino acids do not all need to be sourced from a single meal but can come from the meals and snacks you eat throughout the course of a day. The recommended daily allowance depends on the amino acid and varies between authorities like the Cleveland Clinic and the World Health Organization. For every 1 kilogram (2.2 pounds) of body weight, you should consume the following amounts of each essential amino acid:
- Phenylalanine: 25 to 33 milligrams
- Valine: 24 to 26 milligrams
- Threonine: 15 to 20 milligrams
- Tryptophan: 4 to 5 milligrams
- Methionine: 10 to 19 milligrams
- Leucine: 39 to 42 milligrams
- Isoleucine: 19 to 20 milligrams
- Lysine: 30 to 38 milligrams
- Histidine: 10 to 14 milligrams
What Foods Contain Amino Acids?
All foods that contain protein will inevitably contain amino acids. Single protein sources that contain all nine of the essential amino acids are sometimes called complete proteins.
What Foods Contain All Nine Essential Amino Acids?
Complete proteins that contain all nine essential amino acids are often associated exclusively with animal products, like beef, poultry, fish, eggs and dairy. However, plant-based sources of protein also contain all the essential amino acids, even though some may be present in only small quantities. Still, there are several plant-based complete proteins, most notably whole sources of soy, such as tofu, edamame, tempeh and miso, and grains like quinoa and buckwheat.
The simplest way to get all essential amino acids is to eat a varied diet from a range of vegetables, legumes, nuts, seeds and whole grains. It is definitely possible to get all your amino acids as a vegan.
Should I Take Amino Acid Supplements?
There’s no evidence that supplements provide more essential amino acids or are more effective than simply eating a balanced and varied diet.
A growing number of athletes and fitness enthusiasts have turned to what are called BCAA supplements, which contain three of the essential amino acids — leucine, isoleucine and valine — and are considered branched-chain amino acids (BCAAs). Supplement companies claim these can improve athletic performance, stimulate muscle recovery and reduce muscle soreness or damage after exercising. However, even though a small number of studies have shown some very minimal positive impacts, there is no evidence that supplements offer any better results than what you get from a healthy diet. In fact, that is essentially the case for all supplements with few exceptions, like folic acid for pregnant women.
Ultimately, dietary supplements are not regulated by the Food and Drug Administration (FDA) for safety and effectiveness. And because amino acid supplements can sometimes interact with medications, seek professional medical advice before taking this or any other supplement.
Should Kids or Young Adults Take Amino Acids?
Currently, there are very few long-term studies examining the safety of amino acid supplements for children and very young adults. Because supplements aren’t more effective than a healthy diet and are not regulated by the FDA, consult with a pediatrician for more information, and a registered dietitian for information about nutrition for young adults and children.
What Should I Look for in an Essential Amino Acid Supplement?
There’s no evidence that supplements do a better job at providing essential amino acids than simply eating a balanced and varied diet. The vast majority of evidence does not support taking any supplement, with a few exceptions, including B12 for anyone following a vegan diet.
What You Can Do
If you eat a reasonably healthy and varied diet, you do not need to worry about your exact intake of essential amino acids.
All essential amino acids can be found in a variety of plant-based foods, even if not from one single food source. If you are concerned, consult with a doctor or registered dietician.