Amino Acids
Essential Amino Acids (Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine)
The nine amino acids that the body cannot synthesize and must obtain from diet for protein synthesis, metabolism, and vital functions
Quick Facts
Daily Needs
Adult RDIs (mg/kg/day): Histidine (10), Isoleucine (20), Leucine (39), Lysine (30), Methionine+Cysteine (15), Phenylalanine+Tyrosine (25), Threonine (15), Tryptophan (4), Valine (26)
Importance
Essential amino acids are critical building blocks for protein synthesis, enzyme function, neurotransmitter production, and numerous metabolic processes.
Key Functions
- •Protein synthesis and muscle building
- •Enzyme and hormone production
- •Neurotransmitter synthesis
- •Immune system support
- •Energy production
- •Transport and storage of nutrients
- •Tissue repair and wound healing
- •Regulation of gene expression
- •Support of gut health and digestion
- •Maintenance of acid-base balance
- •Detoxification processes
Deficiency Signs
- •Muscle wasting or weakness
- •Fatigue and low energy
- •Poor wound healing
- •Hair thinning and loss
- •Skin problems and rashes
- •Weakened immune function
- •Mood changes (anxiety, depression)
- •Growth impairment in children
- •Digestive issues
- •Edema (swelling)
- •Hormonal imbalances
- •Reduced cognitive function
Excess Signs
- •Generally safe within reasonable dietary intake
- •Very high supplemental intake may cause gastrointestinal distress
- •Potential for amino acid imbalances with single amino acid supplementation
- •Ammonia production with excessive intake
- •Potential kidney stress in susceptible individuals
- •Specific amino acids may have unique concerns (e.g., branched-chain amino acids)
Best Food Sources
- •Animal proteins (meat, poultry, fish, eggs, dairy)
- •Soy and soy products (tofu, tempeh, edamame)
- •Quinoa (complete protein)
- •Buckwheat
- •Hemp seeds
- •Spirulina and other algae
- •Combinations of legumes and grains
- •Nuts and seeds
- •Nutritional yeast
- •Protein powder supplements (whey, plant-based blends)
Absorption Facts
- •Absorbed in the small intestine
- •Compete with each other for absorption when in free form
- •Rate of absorption varies by amino acid
- •Generally high bioavailability from animal sources
- •Plant proteins typically have lower digestibility and bioavailability
- •Processing methods (cooking, fermenting, sprouting) can improve absorption from plants
- •Digestive health affects absorption efficiency
- •Absorbed better when consumed as part of whole proteins than as individual supplements
- •Aging may reduce absorption efficiency
- •Stress and illness can increase requirements
Special Considerations
- •Athletes and active individuals have increased protein and amino acid needs
- •Older adults often require more protein due to anabolic resistance
- •Vegetarians and vegans need variety in plant proteins to get all essential amino acids
- •Complete protein sources contain all nine essential amino acids in adequate proportions
- •Protein combining at each meal is not necessary - balance over the day is sufficient
- •Pregnancy and breastfeeding increase amino acid requirements
- •Certain medical conditions may require modified amino acid intake
- •Growth periods (childhood, adolescence) have higher requirements
- •Branched-chain amino acids (leucine, isoleucine, valine) have special roles in muscle metabolism
- •Specific amino acids may be conditionally essential during illness or stress
About Essential Amino Acids (Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine)
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