Proteins are responsible for most bodily structures and functions. Amino acids are responsible for constructing and regulating proteins. Every protein in the human body is encoded by 21 core amino acids, but nine of those nutrients can never be synthesized in the body, and six more can only be synthesized under certain conditions. To maintain vital bodily functions, these essential nutrients must be consumed from dietary sources. See: Proteins for an overview of complete proteins and where to find them.
Essential
Can never be synthesized in the human body, must be consumed from dietary sources.
Branched-Chain Amino Acids
Promote protein synthesis for muscle growth, encourage retention and reuse of amino acids in muscle cells, and reduce protein breakdown in muscle loss and fatigue. Vitamin B7 is required to assist break down and absorption, inefficient biotin levels when metabolizing branched-chain amino acids can lead to a condition known as Maple Syrup Urine Disease.
Leucine
Most effective in promoting protein synthesis for muscle growth and repair. Leucine stimulates production of insulin in the pancreas and promotes muscle cell absorption of blood glucose without use of insulin but inhibits insulin-stimulated absorption. May lower levels of serotonin and dopamine in the brain.
- Optimal herbivorous food sources for leucine– avocado, sea vegetables, pumpkin, rice, watercress, turnip greens, soy, peas, beans, figs, raisins, dates, apples, blueberries, bananas, olives, nuts and seeds.
Isoleucine
Less effective in encouraging protein synthesis for muscle building, but more effective in reducing blood sugar for use as energy during exercise. Isoleucine has no effect on insulin or glucose production, but it increases absorption of glucose into muscle cells without insulin resistance, and significantly increases energy output during exercise.
- Optimal herbivorous food sources for isoleucine– grains, legumes, leafy greens, berries, nuts and seeds.
Valine
Least effective in muscle building and most resistant to insulin-stimulated blood sugar regulation. Valine aids in removal of excess nitrogen from the liver and transport as needed, reducing and possibly reversing the effects of liver and gallbladder disease. Valine deficiency has been indicated in degenerative neurological conditions characterized by damage to the fatty myelin layer that insulates nerve cells.
- Optimal herbivorous food sources for valine– beans, legumes, soy, mushrooms, spinach, broccoli, peanuts, avocado, apples, berries, oranges, figs, apricots, grains, nuts and seeds.
Optimal food sources for branched-chain amino acids
- Fish– two 4 ounce servings will meet daily requirements
- Eggs
- Dairy
- Soy
- Sea vegetables
Sulfur Containing Amino Acids
Aid in the detoxification of potentially harmful substances in the body.
Methionine
Crucial component in methylation, converts toxins into water-soluble substances to prepare for excretion. Arsenic, mercury, lead, and aromatic hydrocarbons, among other potentially toxic substances, require methylation as part of detoxification.
- Optimal herbivorous food sources for methionine– oats, rice, beans, soy, legumes, sea vegetables, onions, chocolate, dried fruits, nuts and seeds.
Cysteine
Can be synthesized from serine if sufficient methionine levels are present. Cysteine works with dispensable amino acids glycine and glutamic acid to form glutathione, a powerful antioxidant, and binding molecule required to enable detoxification of certain toxins including pesticides and methyl bromides.
- Optimal herbivorous food sources for cysteine– soy, oats, bell peppers, legumes, grains, nuts and seeds.
Optimal food sources for sulfur containing amino acids
- Fish– one 4 ounce serving will meet daily requirements
- Legumes
- Nuts and Seeds
Aromatic Amino Acids
Absorb ultraviolet rays to release energy or emit light. Tryptophan has the strongest fluorescent properties followed by tyrosine and phenylalanine. Herbicides and antibiotics inhibit synthesis of aromatic amino acids, rendering them toxic to plants and micro-organisms that rely on this process to sustain vital functions. Humans and other animals are built to function without the necessary components to synthesize aromatic amino acids, but exposure to herbicides and antibiotics can still inhibit utilization of these essential nutrients and may have negative impact in other systems of the body. When consumed by humans, aromatic amino acids work with B-complex Vitamins to regulate hormone production and mental health.
Tryptophan
Used in synthesis of Vitamin B3 (niacin), can be converted into the hormones serotonin and melatonin by certain cells in the nervous system. Turkey meat has high levels of tryptophan, when consumed in excess this can cause drowsiness, but the real culprits behind the Thanksgiving nap are serotonin and melatonin.
- Optimal herbivorous food sources for tryptophan– quinoa, soy, nuts, seeds, oats, sea vegetables, squash, roots, mushrooms, asparagus, leafy greens, avocado, peppers, figs, apples, oranges, bananas, beans and legumes.
Phenylalanine
Regulates central nervous system functions and aids in production of the hormones melatonin, dopamine, noradrenaline and adrenaline. Phenylalanine can cross the blood-brain barrier, making it particularly effective in regulation of pain, appetite, mood and concentration.
- Optimal herbivorous food sources for phenylalanine– soy, sea vegetables, pumpkin, avocado, beans, legumes, rice, quinoa, dried fruits, leafy greens, berries, olives, nuts and seeds.
Tyrosine
Regulates pain sensitivity, metabolism, mood and stress response mechanisms. Tyrosine is required to metabolize phenylalanine, which is required to produce tyrosine. Both tyrosine and phenyalanine are required to synthesize the hormones dopamine, noradrenaline and adrenaline.
- Optimal herbivorous food sources for tyrosine– soy, nuts, seeds, grains, beans and legumes.
Histidine
Essential in tissue growth and repair, production of red and white blood cells, and detoxification of toxic metals. Histidine works with Vitamins B3 and B6 to produce histamine, which aids in digestion, triggers immune response to allergens, and stimulates sexual arousal. Deficiency can contribute to Rheumatoid Arthritis and deafness due to nerve damage.
- Optimal herbivorous food sources for histidine– cantaloupe, sea vegetables, potatoes, cauliflower, corn, soy, nuts, seeds, grains, beans and legumes.
Optimal food sources for aromatic amino acids
- Fish
- Meat
- Tofu
- Legumes
- Nuts and Seeds
One 4 ounce serving of beans, tofu, fish or chicken will exceed daily nutrient requirements for tryptophan.
Other Essential Amino Acids
Aid in production of antibodies to maintain essential immune system functions, protect from tissue damage and promote wound healing .
Lysine
Aids in production of antibodies, promotes collagen and protein synthesis, blocks absorption of argenine in herpes virus replication. Lysine is required in the formation of chromatin used to regulate genetic processes in cell nuclei.
- Optimal herbivorous food source for lysine– soy, beans, legumes, watercress, parsley, avocados, nuts and seeds.
Threonine
Aids in production of antibodies, digestion of fats, bone building and wound healing. Threonine is required in the formation of mucins used to protect intestinal linings, and for production of glycine and serine used in formation of muscle proteins collagen and elastin.
- Optimal herbivorous food sources for threonine– soy, watercress, spirulina, pumpkin, leafy greens,avocados, dried fruit, grains, bean, legumes, nuts and seeds.
Optimal food sources for other essential amino acids
- Legumes
- Tofu
- Dairy
- Eggs
- Nuts and Seeds
- Fish and Chicken– one 4 ounce serving will exceed daily requirements for lysine
Conditionally Essential
Can only be synthesized in the human body under certain conditions, dietary supplementation generally required to maintain vital bodily functions.
Arginine
Can be synthesized from disposable nutrient glutamic acid via proline and glutamine, but the process releases a lot of energy in the form of ATP that can be preserved by increasing dietary intake. Preterm and newborn babies cannot synthesize arginine internally, rendering it an essential nutrient in these stages of development, but a disposable amino acid for adults. Arginine stimulates the thymus gland, increasing production of t-cells in the immune system. In the liver, arginine is required for production of urea, allowing the body to excrete toxic ammonia through urination. Found in high concentrations in the skin, arginine helps process creatine to build and repair muscle tissue, and nitrogen for use in muscle metabolism. Nitric oxide, responsible for relaxing blood vessel contractions, requires arginine as a precursor. Arginine promotes production of insulin hormones in the pancreas, vasopressin hormones in the pituitary glands, and growth hormones in developing humans. Arginine deficiency is indicated in delayed sexual maturity and male sterility.
- Optimal food sources for arginine– spirulina, coconut, dairy, soy, chocolate, meat, nuts, seeds, grains, wheat germ, gelatin, beans and legumes.
Glutamine
The most abundant amino acid in blood and muscle tissues. Glutamine promotes cell division serving as a crucial component in development of the immune system and synthesis of DNA and RNA. Glutamine can pass through the blood-brain barrier to regulate central nervous system functions. Inside the brain, glutamine can be converted into disposable amino acids GABA and glutamic acid. If glucose supply is insufficient, glutamine can be metabolized as an alternative energy source for the nervous system. In the liver, excess nitrogen bonds with glutamic acid to form glutamine instead of ammonia toxins. Glutamine protects the liver from drug and alcohol poisoning, and transports excess nitrogen throughout the body as needed. By replenishing nitrogen and glycogen supplies in muscle tissues, glutamine prevents muscle degradation after strenuous activity.
- Optimal food sources for glutamine– beef, chicken, fish, dairy, eggs, beans, beets, carrots, parsley, wheat, papaya, celery and raw leafy greens. Glutamine is easily deteriorated by cooking.
Proline
Can be synthesized from disposable nutrient glutamic acid. Proline works with lysine to form collagen, essential in building and repairing skin, cartilage, muscle and connective tissues. If blood glucose levels are insufficient to sustain prolonged activity, the body will burn muscle mass for energy. To prevent muscle loss, increase dietary proline intake if highly active or recovering from traumatic tissue damage.
- Optimal food sources for proline– meat, dairy, eggs, fish, soy, brewer’s yeast, cabbage, spinach, watercress, asparagus, avocado, cucumber, sea vegetables, sprouts, nuts, seeds, grains, beans and legumes.
Glycine
Can be synthesized from serine under certain conditions in the body. Glycine aids in protein synthesis for muscle growth, conversion of glucose into energy, construction of DNA and RNA, and maintenance of nervous and digestive systems. Found in skin, muscle and connective tissue, glycine is a major component in the structural protein collagen. Glycine prevents muscle loss by promoting creatine production, regulates blood sugar by promoting absorption of glucose into muscle tissue, protects from free radical damage via antioxidant properties, acts as a neurotransmitter in the central nervous system, and synthesizes gastric bile acids for use in digestion.
- Optimal food sources for glycine– fish, beans, dairy, meat, soy, spinach, kale, cabbage, cauliflower, pumpkin, cucumber, kiwi and banana.
Zu-Zu Lee 