PVT TIM HALL

Essential amino acids are amino acids that cannot be synthesized by the human body and must be obtained from one's diet. Amino acids are the building blocks of proteins, play a role in the formation of neurotransmitters and hormones, and serve as an energy source for the body. Each amino acid contains an α-carboxyl group, a primary α-amino group, and a side chain referred to as the R group. While there are hundreds of amino acids, the body needs 20 different amino acids to synthesize all protein. These include alanine, arginine, cysteine, glutamine, glycine, proline, asparagine, aspartic acid, glutamic acid, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, serine, threonine, tryptophan, tyrosine, and valine. 

Amino acids are classified into three groups nutritionally: essential, non-essential, and semi-essential. In contrast to essential amino acids, non-essential amino acids are synthesized by the body and not primarily derived from diet. Semi-essential, also referred to as conditionally essential amino acids, are produced in sufficient quantities in healthy individuals, however, can become essential during specific physiological periods of growth, including pregnancy, lactation, adolescent growth, or recovery from physical trauma and injury.  

Foods that contain all nine essential amino acids are called complete proteins and include meat (e.g., beef, poultry, fish), eggs, and dairy. Soy products and some grains (e.g., quinoa and buckwheat) are also considered complete proteins. In contrast, incomplete proteins are foods that contain some but not all the essential amino acids such as nuts, seeds, and beans.  

The “P” in PVT TIM HALL represents phenylalanine which is involved in the production of neurotransmitters including dopamine, epinephrine and norepinephrine and in the production of other amino acids (i.e., tyrosine). In addition to protein sources, other sources of phenylalanine include products sweetened with the artificial sweetener aspartame, like diet drinks and food. Phenylalanine is typically closely monitored and oftentimes restricted in the diet of those with phenylketonuria (PKU). PKU is a genetic condition that results in the lack of production of an enzyme called phenylalanine hydroxylase (PAH), which breaks down phenylalanine. Those with PKU may accumulate toxic levels of phenylalanine resulting in central nervous system damage.  

The average adult without PKU is recommended to intake 25 mg/kg of phenylalanine daily.  

Low phenylalanine levels may be associated with eczematous rashes, hair loss, problems with vision, diarrhea, and failure to thrive in infants. 

The “V” in PVT TIM HALL represents valine, an amino acid involved muscle growth and tissue repair. Valine, leucine, and isoleucine, are known as branched-chain amino acids, which refers to their branched chemical structure. Examples of valine-rich foods include meat (i.e., beef, pork, sheep, goat, veal) and grain products (i.e., rice, wheat). A genetic disease associated with faulty catabolism of branched-chain amino acids includes maple syrup urine disease, named after the characteristic odor of the urine. Maple syrup urine disease results from a defect in the branched-chain a-keto acid dehydrogenase enzyme which breaks down valine, leucine, and isoleucine. Accumulation of these branched-chain amino acids can result in central nervous system toxicity.   

An average healthy adult requires about 24 mg/kg of valine daily.  

Prolonged valine deficiency, as with all essential amino acids, may result in growth failure, loss of muscle mass, and organ damage. 

The “T” in PVT TIM HALL represents tryptophan, an amino acid that plays a role in the synthesis of neurotransmitters including serotonin (i.e., a regulator of mood and appetite) and melatonin (i.e., a regulator of the circadian rhythm controlling sleep cycles). The liver can also use tryptophan to produce niacin (i.e., vitamin B3), which is needed for energy metabolism and DNA production. Some common sources of tryptophan are oats, bananas, dried prunes, milk, tuna fish, cheese, bread, chicken, turkey, peanuts, and chocolate.  

Adults are thought to require 6mg/kg per day.   

Tryptophan deficiency may result in changes in mood including aggression, impulsivity, and impairments in learning and memory skills. 

The second “T” in PVT TIM HALL represents threonine, which plays an important role in the formation of collagen and elastin, which are proteins that provide structure and elasticity to the skin. Threonine also plays a role in forming a mucosal barrier in the gastrointestinal tract which protects against digestive enzymes and plays a supportive role in immune system function. Some common sources of threonine include cottage cheese, poultry, fish, meat, lentils, and sesame seeds.  

The threonine requirement of adults is thought to be more than 500 mg/day.   

Threonine deficiency may result in growth failure, loss of muscle mass, and organ damage. 

The “I” in PVT TIM HALL represents isoleucine. Isoleucine is involved in producing hemoglobin, the oxygen-carrying protein in red blood cells. It also plays a role in muscle metabolism, immune function, and regulation of energy. Examples of foods containing isoleucine include tuna, soybeans, chicken, and pork. 

Adults are thought to require at least 23 mg/kg per day.  

Isoleucine deficiency is more common in older people and may be associated with the weakening and wasting of muscle (i.e., sarcopenia) and tremors.   

The “M” in PVT TIM HALL represents methionine, which plays a role in tissue growth, metabolism, and detoxification. Methionine also helps with the absorption of essential minerals, including zinc and selenium. Methionine is commonly found in nuts, beef, lamb, cheese, turkey, pork, fish, shellfish, soy, eggs, dairy, and beans. Metabolically, methionine is a precursor to the amino acid cystine. Homocystinuria is an inherited disorder characterized by defects in methionine metabolism, specifically a lack of the enzyme cystathionine beta-synthase, leading to accumulation of the amino acid homocysteine, which is an intermediate in methionine metabolism. This results in blood clots, dislocation of the lens of the eye, central nervous system and skeletal abnormalities (e.g., scoliosis), and intellectual disability.  

Since methionine and cystine are metabolically related, the recommendation is for healthy adults to get at least 13mg/kg per day of a combination of both amino acids.  

Methionine deficiency is associated with hair loss, liver dysfunction, and neural tube defects in those who are pregnant. 

The “H” in PVT TIM HALL represents histidine. Histidine is involved in erythropoiesis (i.e., the formation of red blood cells); scavenging reactive oxygen and nitrogen species, also known as free radicals; and the formation of the neurotransmitter histamine. Histamine plays a crucial role in the body’s response to allergens, inflammation, and immune system response. Histidine is found in foods such as meat, chicken, fish soybean, kidney beans, peas, oat, and wheat. Histidine supplementation has been used to treat rheumatoid arthritis and anemia in patients with chronic renal failure and may have potential benefits for those with atopic dermatitis and inflammatory bowel disease.  

Adults are thought to require about 11-14 mg/kg per day of the amino acid histidine.  

Histidine deficiency may be associated with growth failure and skin dysfunction and various cutaneous diseases.  

The “A” in PVT TIM HALL represents arginine. Arginine can be considered conditionally essential depending on the health status and developmental stage of the individual. For example, in neonates, arginine is an essential amino acid that must be provided in the diet for growth and development. For healthy adults, arginine is produced in sufficient quantities. However, under times of stress such as during trauma, burn injury, small-bowel resection, and renal failure, arginine becomes essential, and must be replaced via one's diet. Foods rich in arginine include meat (e.g., red meat, chicken, turkey), fish (e.g., salmon, haddock), and nuts and seeds (e.g., almonds, cashews, pumpkin seeds). Arginine plays a role in T-cell function, in the formation of nitric oxide (NO) which is a potent vasodilator, and in inflammatory response. L-Arginine supplementation has been used in various health conditions including angina (i.e., chest pain), hypertension, and erectile dysfunction due to its vasodilatory effects. 

Estimates of daily arginine requirements vary depending on one’s health condition.  

Arginine deficiency may result in T-cell dysfunction, immunodeficiency, and cardiovascular dysfunction. 

The “L” in PVT TIM HALL represents lysine. Lysine is involved in calcium regulation (i.e. it increases absorption of calcium), collagen formation, immune function, and in the production of carnitine, a compound that helps convert fatty acids into energy. Lysine has been used clinically to help treat herpes simplex virus (HSV), osteoporosis, and may help muscle tissue recover after stress. Lysine can be found in poultry, fish, shrimp, shellfish, pork, beef, soy, nuts, seeds, eggs, beans, and lentils.  

The daily lysine requirement is approximately 30 mg/kg in healthy adults.   

Lysine deficiency may result in delayed growth, anemia, and reproductive disorders.  

The second “L” in PVT TIM HALL represents leucine. Leucine is involved in muscle growth and repair; energy balance; controls food intake through regulation of leptin, a hormone that regulates appetite; and regulates blood sugar levels through mammalian target of rapamycin (mTOR) activation. mTOR is involved in the regulation of many cellular processes, including protein synthesis and cell growth, proliferation, and survival. Some examples of leucine-rich foods include eggs, beans, pumpkin seeds, lentils, peanuts, and oats. 

The daily leucine requirement for an average adult is thought to be more than 40 mg/kg per day.  

Leucine deficiency may be associated with muscle weakness and fluctuation in blood sugar levels.