Amino acids are the building blocks of proteins. They are required for the formation and maintenance of everything from blood, muscle, skin and bone to hormones, enzymes and neurotransmitters and make up three quarters of our "dry" weight.

Our bodies make more than 50,000 proteins from at least 20 different amino acids. Of these, nine are particularly important because the body cannot make them. These essential amino acids (EAAs) must be provided by our food.

Our needs vary. Children require a tenth EAA and a higher proportion of their amino acids to be the essential forms than do adults. Overall requirements go up with increased weight and height, but exercise, trauma or illness, pregnancy and lactation demand more. Recommended daily intakes range from about 25 grams per day for young children to 50 grams daily for teenagers, 55 grams for women, 60 grams for men 65 grams for pregnancy and 75 grams for lactation.

Vegetarian sources are excellent: one cup of peanuts supplies 37 grams; a cup of almonds 26 grams; a cup of Brazil nuts or cooked split peas 20 grams and a cup of beans or cooked barley about 16 grams. The amino acids in whole grains complement those in nuts, seeds and beans. Surprisingly, even such foods as spinach, broccoli, brussels sprouts, collards and other greens–even mushrooms–supply five grams per cup. Potatoes and onions actually contain three grams of protein per cup.

Can’t Live Without ‘Em

The nine essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylanaline, threonine, tryptophan and valine. Children and certain adults also need arginine, an amino acid we normally produce as adults.

Arginine promotes growth hormones and glandular development. It’s the main substance in sperm. Peanuts, cashews, pecans, almonds, chocolate and seeds are rich sources.

Histidine is metabolized into the neurotransmitter histamine and is involved in smooth muscle function and blood vessel contraction/dilation. It’s significant for the growth and repair of tissues. It’s also important for the protection of nerve cells and the production of red and white blood cells. It can help chelate heavy metals. Natural sources include rice, rye and wheat.

Isoleucine is needed for production of hemoglobin and also regulates blood sugar and energy levels. A deficiency of isoleucine results in symptoms similar to hypoglycemia. Food sources include almonds, cashews, chickpeas, pumpkin seeds, sunflower seeds, eggs, lentils, rye and soy protein. It is available in supplemental form and should be taken with leucine and valine.

Leucine, along with isoleucine and valine, are branch-chained amino acids used first by the body during exercise to protect muscle and act as fuel. They also promote healing of bones and skin tissue. Leucine helps to lower elevated blood sugar levels and increases growth hormone production. Natural sources include eggs, brown rice, beans, almonds, Brazil nuts, cashews, chickpeas, lentils, corn and whole wheat and soy flour.

Lysine helps calcium absorption and maintains proper nitrogen balance as well as aiding in the production of hormones and enzymes. It contributes to tissue repair and helps to build muscle protein. Food sources of lysine include eggs, cheese, milk, brewer’s yeast, lima beans, potatoes, mung bean sprouts and soy products.

Methonine assists in the break down of fats, helping to prevent buildup in the liver and arteries. It’s a powerful anti-oxidant and antihistamine and contains sulphur, which protects against radiation. Sources include beans, eggs, garlic, lentils, onions, soybeans, sesame seeds and yogurt.

Phenylanaline is synthesized inside the body into tyrosine, another amino acid, producing neurotransmitters like epinephrine and promoting mental alertness. Because of its relation to the nervous system, phenylanaline can help to elevate mood, decrease pain and aid in memory, learning and appetite suppression. Sources are cottage cheese, soybeans, almonds, Brazil nuts, pecans, pumpkin and sesame seeds, lima beans, chickpeas and lentils.

Threonine helps to maintain a proper balance of proteins in the body. It is important for the formation of collagen and elastin and aids liver function. It also helps to prevent fatty buildup in the liver. It’s useful in the treatment and prevention of mental illness. Deficiency causes irritability. Because the threonine content of grains is low, vegetarians should also consume pulses.

Tryptophan is necessary for the production of vitamin B3 (niacin). It’s used by the brain to produce serotonin; consequently it helps to combat depression and insomnia and stabilize moods. It’s also good for migraine headaches and may reduce some of the effects of nicotine. The best dietary sources of tryptophan include nutritional yeast, brown rice, cottage cheese, peanuts, pumpkin and sesame seeds and soy protein.

Valine has a stimulant effect. It is needed for muscle metabolism and tissue repair as well as maintaining the body’s proper balance of nitrogen. Natural sources include cottage cheese, almonds, Brazil nuts, cashews, brown rice, mushrooms, peanuts, soy proteins, lentils and lima beans.

Supplemental amino acids are available in combination with various multi-vitamin formulas, as well as protein mixtures and a number of specific formulas. Amino acids supplements are derived from yeast and vegetable proteins so they are suitable for vegans and vegetarians. Most amino acids (except for glycine) come in two forms, the chemical composition of one being the opposite of the other. These are called the D (dextro, Latin for right) and L (levo, Latin for left) forms. Products containing the L form are considered to be more compatible to human chemistry.

Too Much Makes Too Little

Excessive protein in the diet can actually cause a protein deficiency! The reason is pancreatic overload.

The pancreas helps to break down protein by producing proteolytic enzymes. But too much protein, sugar, alcohol or processed fat as well as drugs, coffee and tobacco can reduce pancreatic function. The result is that protein molecules may be absorbed undigested, provoking inflammatory reactions even in distant organs and tissues. The exhausted pancreas cannot produce the anti-inflammatory enzymes, either. The resulting protein deficiency causes the body to try to compensate, depleting vitamins and minerals, particularly pyroxidine, zinc and magnesium.

About the Author

Corinna Richards is a freelance health writer based in Atlanta, Ga.