PROTEIN INFORMATION

Proteins are polymers of amino acids that contain the elements carbon, hydrogen, oxygen, nitrogen and sulfur. Particular emphasis is given to the indispensable amino acids, i.e., those that must be in the food supply because they either cannot be synthesized in the body or they cannot be synthesized in adequate quantity to meet the needs for optimal rates of growth in children. The indispensable amino acids are: lysine, methionine, threonine, tryptophan, leucine, isoleucine, valine, phenylalanine, arginine and histidine. A dietary supply of arginine is not required by adults. The amino acids supplied from dietary protein are needed for synthesis of body proteins in muscle, organs, bone and skin, and for synthesis of enzymes, certain hormones, antibodies and a host of specialized products.

AMINO ACIDS

Essential Amino Acids- These must be supplied to the body from food or supplements.

HISTIDINE:

• essential in children

• supplementation not recommended ( may suppress immune system when combined with exposure to sun)

• Precursor of the neurotransmitter histamine, and the dipeptides carnosine and homocarnosine.

ISOLEUCINE:

• a branched-chain amino acid readily taken up and used for energy by muscle tissue

• used to prevent muscle wasting in debilitated individuals

LEUCINE:

• a branched-chain amino acid readily used as a source of energy

• helps reduce muscle protein breakdown

• used to synthesize enkephalins (natural painkillers similar to endorphins)

• competes with tyrosine, phenylalanine, tryptophan (used to make neurotransmitters) and other branched-chain amino acids for uptake by the brain

• promotes healing of skin and broken bones

LYSINE:

• low levels can slow protein synthesis, affecting muscle and connective tissue

• inhibits viruses and may reduce flare-ups in those suffering from herpes simplex

• needed for carnitine synthesis

• aids bone growth by helping to form collagen, the fibrous protein that makes up bone, cartilage and other connective tissue

METHIONINE:

• precursor of cysteine, creatine, and carnitine

• may increase antioxidant levels (glutathione)

• increases both total cholesterol and LDL cholesterol levels if taken in excess

• bolsters drug detoxifying activity in the liver (by way of glutathione)

• used to make cysteine, an important component of keratin protein that makes up hair and fingernails

PHENYLALANINE:

• l-phenylalanine is the major precursor of tyrosine (see tyrosine)

• enhances mood and alertness but may cause irritability

• d- and l-phenylalanine isomers are used to treat some types of depression (alone or in a combination called DLPA)

• d-phenylalanine increases enkephalins (natural painkillers) by inhibiting enkephalin breakdown enzymes; useful in chronic pain management

• a major element in the production of collagen

• suppresses appetite by increasing brain norepinephrine levels

• found in NurtaSweet (aspartame)

THREONINE:

• deficiency causes fatty buildup in the liver

• important component of collagen’

• generally low in vegetarians

• important to build the immune system

TRYPTOPHAN:

• precursor of key neurotransmitter serotonin, which exerts a calming effect

• used in treatment of insomnia, stress, anxiety and depression

• free form of this amino acid is not available individually in the U.S. at present; available only in natural food sources and the more potent direct serotonin precursor 5-hydroxytryptamine (5-HTP)

VALINE:

• a branched-chain amino

• not processed by the liver; rather actively taken up by muscle tissue

• influences  brain uptake of other neurotransmitter precursors (tryptophan, phenylalanine and tyrosine)

Nonessential Amino Acids. These can be synthesized by the body from other amino acids.

ARGININE:

• increases  nitric oxide, a muscle-building gas formed at the ends of muscle fibers

• can increase the secretion of insulin, glucagons and growth hormones (but not in oral doses)

• important for muscle metabolism; transports, stores and excretes nitrogen

• reduces muscle breakdown in rodents and possibly burn patients

• aids in injury rehab, formation or collagen and immune system stimulation

• precursor of creatine

• may increase sperm count, reduce some forms of impotence and increase T-lymphocycle response

CYSTEINE:

• detoxifies harmful chemicals in the liver

• helps prevent damage from alcohol, tobacco and Tylenol use

• necessary for synthesis of hair proteins

• N-Acetyl Cysteine (NAC) form improves glutathione levels and immune response in AIDS patients (but not necessarily healthy people)

TYROSINE:

• precursor of the neurotransmitters dopamine, norepinephrine and epinephrine, as well as thyroid and growth hormones and melanin, the pigment responsible for skin and hair color

• elevates mood but may cause irritability

• curbs appetite

ALANINE:

• major component of connective tissue

• key intermediate in the glucose-alanine cycle, which allows muscles and other tissues to derive energy from amino acids

ASPARTIC ACID:

• involved in some aspects of muscle energy metabolism

• some studies suggest salts of aspartic acid increase stamina and endurance (others don’t)

• found in NutraSweet (aspartame)

GLUTAMIC ACID:

• a major precursor of glutamine, glutathione and GABA (a brain chemical)

• important in brain metabolism and the metabolism of other amino acids

GLUTAMINE:

• most abundant amino acid

• plays a key role in immune system functions

• an important source of energy, especially for the kidneys, intestines and liver during caloric restriction

• may improve cognitive performance

GLYCINE:

• aids manufacture of other amino acids and is part of the structure of hemoglobin and cytochromes (enzymes involved in energy production)

• may have a calming effect

• produces glucagons, which mobilizes glycogen

• used in creatine synthesis

ORNTHINE:

• increases nitric oxide (a muscle-building gas) at the ends of muscle fibers

• involved in urea metabolism, dealing with the byproducts of protein breakdown

PROLINE:

• a major component in the formation of connective tissue and heart muscle

• major constituent of collagen

SERINE:

• important in energy production

• aids memory and nervous systems function

• involved in immunoglobulin and antibody production

TAURINE:

• used to make bile salts for fat digestion and absorption (not in protein synthesis)

• may act as a neurotransmitter in some areas of the brain and retina

AMINO ACIDS- FORMS AND FUNCTION

FREE-FORM                                        
Doesn’t require digestion; rapid absorption

HYDROLYZED PROTEIN                      
Pre-digestion speeds absorption

BRANCHED-CHAIN                              
Increases ammonia production during exercise, which aids in formation of alanine from glucose

DI-/TRIPEPTIDES                                 
Two and three amino-acid molecules that are quickly absorbed

PLANT PROTEINS                                
Proteins appropriate for vegans, vegetarians and omnivores (chiefly from legumes, nuts, grains)

ANIMAL FOODS                                   
Dairy, poultry, eggs, beef, etc., rich in essential amino acids