Amino acids are the essential building blocks of proteins, molecules crucial to life itself. Thanks to them, our bodies build and repair tissues, produce hormones, enzymes, and neurotransmitters, and keep countless vital biological processes running. Does that sound important? It certainly is! In this article, we will explore what amino acids are, how they are classified, the history of their discovery, where to get them, and why they matter so much for your health and physical performance.
1. What are amino acids?
Amino acids are organic compounds that have an amino group (-NH2) and a carboxyl group (-COOH). When several amino acids are linked through peptide bonds, they form proteins. Although more than 300 amino acids have been identified in nature, our bodies mainly use 20 (called “proteinogenic”) to synthesize human proteins.
1.1. A brief historical overview
Did you know that the first amino acid discovered was asparagine? This happened in 1806, thanks to the French chemists Louis-Nicolas Vauquelin and Pierre Jean Robiquet. Throughout the 19th and early 20th centuries, the remaining amino acids were identified and characterized, a milestone that revolutionized our understanding of protein structure and function in biology.
Featured reference:
- Lodish H, et al. (2016). Molecular Cell Biology. 8th Edition. Freeman and Company.
2. Classification of amino acids
Broadly speaking, we distinguish three main groups: essential, nonessential, and conditionally essential.
2.1. Essential amino acids
These amino acids cannot be synthesized by our bodies, or are not produced in sufficient amounts, so we must obtain them through our diet. There are 9:
- Histidine
- Isoleucine
- Leucine
- Lysine
- Methionine
- Phenylalanine
- Threonine
- Tryptophan
- Valine
Their role is critical for protein synthesis, hormone production, immune function, and many other processes.
2.2. Nonessential amino acids
Nonessential amino acids can be synthesized by the body from other organic compounds. This group includes alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine.
2.3. Conditionally essential amino acids
In special circumstances (stress, illness, injury recovery, or periods of rapid growth), some amino acids that are usually nonessential can become “conditionally essential.” A clear example is glutamine, which is in high demand during physical stress such as burns, sepsis, or intensive training.
Featured reference:
- Wu G. (2009). Amino acids: metabolism, functions, and nutrition. Amino Acids. [PMID: 19301095]
3. Main functions of amino acids
- Protein synthesis
- They form muscles, connective tissues, enzymes, antibodies, and hormones.
- Energy production
- In the absence of carbohydrates, they can be used as an alternative fuel (although their main role remains building and repair).
- Nutrient transport and storage
- Some are involved in forming molecules such as hemoglobin, which carries oxygen.
- Metabolic regulation
- They participate in neurotransmitter synthesis (serotonin, dopamine), antioxidant defense (glutathione), and the conversion of ammonia into urea, among other key functions.
4. The role of amino acids in sport and recovery
4.1. Maintaining and gaining muscle mass
- Leucine: Specializes in activating the mTOR pathway, essential for protein synthesis.
- Isoleucine and Valine (BCAA): Together with leucine, they form the trio of branched-chain amino acids. They are widely used to promote recovery and combat fatigue.
4.2. Recovery and reduced muscle damage
Taking essential amino acids after a demanding workout may:
- Speed up protein synthesis
- Reduce delayed-onset muscle soreness (DOMS)
- Help repair microtears in muscle tissue
Featured reference:
- Churchward-Venne TA, et al. (2020). EAA intake to stimulate muscle protein synthesis: a per-meal perspective. Appl Physiol Nutr Metab. [PMID: 32393705]
4.3. Immune function
Physical stress (competitions, long workouts) can affect our immune system. Some amino acids, such as glutamine, are key to maintaining intestinal integrity and supporting the body’s defenses.
5. Dietary sources of amino acids
To ensure a good supply of amino acids, ideally you should consume high-biological-value proteins. If you are wondering where to find them, here are some options:
- Meat and poultry: Chicken, turkey, beef.
- Fish and shellfish: Salmon, tuna, sardines, shrimp.
- Eggs: Notable for the albumin in the white.
- Dairy products: Milk, cheese, and yogurt, which provide casein and whey protein.
- Plant proteins: Legumes (soybeans, lentils, chickpeas), nuts, and seeds (quinoa, chia, hemp), among others.
5.1. Plant combinations for complete profiles
If you follow a vegan or vegetarian diet, combining different plant sources (legumes with whole grains, for example) will help you obtain the full spectrum of essential amino acids. Typical examples:
- Rice and beans
- Whole-wheat bread with peanut butter
- Quinoa with legumes
6. Amino acid supplementation
Although most people can meet their needs through food, there are situations in which supplementation may be useful:
- Athletes and people who exercise: Improve recovery and performance.
- Vegan or vegetarian diets: Ensure all essential amino acids are supplied.
- Clinical situations: Illness, absorption disorders, or periods of stress and fatigue.
6.1. BCAA (Branched-Chain Amino Acids)
BCAAs (leucine, isoleucine, and valine) are popular for:
- Delaying fatigue during prolonged exercise
- Stimulating muscle synthesis
- Supporting recovery after exercise (they reduce catabolism and promote repair)
6.2. EAA (Essential Amino Acids)
They include all nine essential amino acids, providing broader support for protein synthesis. Some experts see EAAs as a more comprehensive long-term option than BCAAs alone.
6.3. Glutamine and other specific amino acids
- Glutamine: Supports intestinal health and facilitates post-workout recovery.
- Arginine: A nitric oxide precursor, it helps vasodilation and could improve performance.
- Taurine: Involved in regulating cellular hydration and muscle contraction.
Note: Guidance from a healthcare or nutrition professional is always recommended before adding supplements.
7. Deficiencies, risks, and precautions
- Insufficient protein intake: Very restrictive diets (such as unplanned vegan diets or eating disorders) can lead to essential amino acid deficiencies, with muscle loss or chronic fatigue.
- Excessive consumption: Excess protein or amino acid intake may overburden the liver and kidneys. Balancing your diet and staying well hydrated are essential.
- Prudent supplement use: Some supplements may interact with medications or be unsuitable if kidney or liver problems are present.
7.1. Myths and facts about amino acids
- Myth 1: “More protein is always better”
Fact: Excess protein is not stored as such and may put stress on your kidneys and liver. - Myth 2: “Plant proteins are inferior”
Fact: The right combination of plant sources can provide a complete amino acid profile. - Myth 3: “Everyone needs supplements”
Fact: Most people get enough amino acids from a balanced diet. Supplements are useful in specific cases.
8. Conclusions
Amino acids are the cornerstone of life, and that is no exaggeration. They are involved in building proteins, regulating hormones, immune function, and proper metabolic function. Maintaining an adequate intake (through diet or supplementation if necessary) is essential for overall well-being and sports performance.
- Balance and variety: Look for foods rich in high-biological-value proteins or combine plant sources.
- Personalization: Adjust your amino acid intake to your goals: muscle gain, weight maintenance, or improved endurance.
- Professional advice: Consult a specialist before starting specific supplements or restrictive diets.
Ultimately, amino acids represent a fascinating world. Despite their small size, their impact on our health and performance is enormous. Make sure you give them the importance they deserve!
Sources Consulted
- Lodish H, et al. (2016). Molecular Cell Biology. 8th Edition. Freeman and Company.
- Wu G. (2009). Amino acids: metabolism, functions, and nutrition. Amino Acids.
- Churchward-Venne TA, et al. (2020). EAA intake to stimulate muscle protein synthesis: a per-meal perspective. Appl Physiol Nutr Metab.
- Wolfe RR. (2017). Branched-chain amino acids and muscle protein synthesis in humans: myth or reality?. J Int Soc Sports Nutr.
- National Institutes of Health (NIH) – Office of Dietary Supplements: Protein and Amino Acids Fact Sheet.
