At any moment, your body is experiencing countless chemical reactions that constantly adapt and regenerate tissue. In every one of those reactions, amino acids are required. Amino acids are the building blocks of all proteins and make up three quarters of your body. Human biochemistry requires 20 types of amino acids. Of those, 12 can be manufactured within your body and the other eight--considered the essential amino acids--must be obtained from the foods you eat.

The eight essential amino acids are leucine, isoleucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Although these compounds are used in thousands of chemical processes--some understood and some unknown--each has a distinctive role.


Together with isoleucine, leucine makes up more than a third of your muscle tissue. For that reason, it's helpful in muscle recovery from exercise and frequently taken as a supplement by athletes to increase endurance.


In addition to helping with muscle recovery, isoleucine helps form hemoglobin, the protein that carries oxygen to other tissues of the body.


When your body rebuilds bones, cartilage, tendons, or ligaments, it uses collagen. To make collagen, it uses lysine and one of its derivatives, hydroxylysine. Lysine helps with calcium absorption in the intestines and helps your immune system with the formation of antibodies.


Working with lysine, methionine helps with collagen synthesis. It's also a good antioxidant, helping your body neutralize destructive free radicals, and break down and metabolizes fats in your liver.


This amino acid is tied to the brain chemistry for appetite, mood, metabolism, and your sleep-wake cycle. It's essential for creating epinephrine, norepinephrine, and thyroid hormones. It's also responsible for production of the amino acid tyrosine.


This amino acid is responsible for a wide range of functions. It's needed for elastin, a substance that lends flexibility to tendons and muscles and helps prevent skin wrinkling. It also helps with collagen formation and is important for the formation of tooth enamel.


Working with phenylalanine, valine helps regulate blood sugar and is essential for tissue repair and growth.


Tryptophan, an amino acid linked with brain chemistry and mood, is needed to make serotonin, a chemical associated with relaxation. Tryptophan is perhaps best known as the amino acid in turkey that causes post-Thanksgiving dinner relaxation and sleepiness. It has been used as a supplement to help with sleeping problems.

Make Sure You're Getting Enough

Each amino acid plays a unique role in your metabolism, but unlike fats and carbohydrates, your body can't store them. Therefore, you need to include amino acids in your daily diet. Fortunately, they're present in a range of foods. Perhaps the best way to get amino acids is to eat proteins that contain all eight of them together: meat, poultry, fish, eggs, and dairy. These sources are known as complete proteins.

If you're a vegetarian or don't eat meat on a daily basis, you can still get all the amino acids. Vegetable sources are known as incomplete proteins, but can be combined to get all of the essential amino acids. Combine grains with legumes (like beans and rice), legumes with nuts or seeds, and nuts and seeds with whole grains (such as peanut butter on whole wheat bread or a salad with chickpeas, served with cornbread).

To make sure you're getting what you need, get at least a tenth of your total daily calories from protein. For example, if you eat 2000 calories per day, 200 should be from protein. You can also divide your body weight (in pounds) by three and set that number as your minimum grams of protein per day. For example, a 150-pound person would need a minimum of 50 grams of protein per day.