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Amino acids are the building blocks of proteins and they're incredibly crucial in the human body. Proteins are central to the work of life, with roles in cell building, substance transport and signalling. Because amino acids are the components of proteins, they play an instrumental role in how proteins function and perform. Some of these amino acids are among many that are termed essential amino acids because they are not made in the human body or have a lower synthesis rate than physiological requirements and are thus necessary to obtain through diet. It's essential to know the nature, functions, and the right intake of essential amino acids to stay healthy and promote growth and development.
Amino acids are organic molecules with an amino group (-NH2) and a carboxyl group (-COOH). Their fundamental molecule is composed of a carbon atom that is linked to an amino group, a carboxyl group, a hydrogen atom, and a specific side chain (R group). The different side chains also gives different amino acids their distinct function and qualities. Amino acids are formed by dehydration condensation reactions, in which the amino atoms attach to the carboxyl atom and create a peptide bond (-CO-NH-). Combining multiple amino acids into a peptide then folds into a protein with a certain three-dimensional shape. Protein diversity and complexity are primarily the product of variations in the number of amino acids and their sequence. There are three types of amino acids, according to whether they can be manufactured in the body: essential amino acids, non-essential amino acids, and conditionally essential amino acids. Essential amino acids cannot be made by the body, or are made only in inadequate amounts, and must be obtained from food. Amino acids that are not essential can be produced in the body, and are not a necessity to be consumed. Conditionally essential amino acids are those that might be required for certain circumstances (like disease or stress).
Fig. 1. 9 Essential amino acids.
There are nine essential amino acids required by the human body, which are: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. These amino acids are termed "essential" because they play irreplaceable roles in the human body. A deficiency in any of them can lead to disruptions in physiological functions, potentially causing a series of health problems.
| Name | CAS | Catalog | Price |
| L-Tryptophan | 73-22-3 | BAT-014312 | Inquiry |
| L-lysine | 56-87-1 | BAT-014299 | Inquiry |
| L-phenylalanine | 63-91-2 | BAT-014318 | Inquiry |
| L-methionine | 63-68-3 | BAT-014309 | Inquiry |
| L-Threonine | 72-19-5 | BAT-014311 | Inquiry |
| L-Isoleucine | 73-32-5 | BAT-014307 | Inquiry |
| L-Leucine | 61-90-5 | BAT-014308 | Inquiry |
| L-Valine | 72-18-4 | BAT-014314 | Inquiry |
| L-Histidine | 71-00-1 | BAT-014306 | Inquiry |
A deficiency in essential amino acids can lead to a series of serious health problems. For example, a lack of lysine can cause symptoms such as stunted growth, weight loss, and anemia; a deficiency in tryptophan may lead to issues like depression and insomnia; and a lack of methionine can affect liver function and trigger diseases like fatty liver. Therefore, ensuring an adequate intake of essential amino acids is crucial for maintaining normal physiological functions and overall health.
Muscle tissue is primarily composed of proteins, and the basic units of proteins are amino acids. During physical activity, muscle fibers are damaged and need to be repaired and rebuilt through protein synthesis. Among the essential amino acids, leucine, isoleucine, and valine are known as branched-chain amino acids (BCAAs), and they play a key role in muscle synthesis. Leucine stimulates muscle protein synthesis and increases muscle volume; isoleucine and valine help improve endurance and reduce muscle fatigue. In addition, muscle growth also requires the synergistic action of other essential amino acids, such as lysine, which promotes the absorption and utilization of protein by muscle cells, thereby accelerating muscle repair and growth.
The immune system is the body's primary defense against external pathogens, and the production and function of immune cells (such as lymphocytes and macrophages) are reliant on proteins. Histidine, an essential amino acid, is a precursor of histamine, which plays a regulatory role in inflammation and promotes leukocyte chemotaxis during immune responses, helping to enhance the body's immune response. Additionally, the other essential amino acids required for protein synthesis provide the necessary material for immune cell proliferation and antibody production, thereby supporting the proper functioning of the immune system.
Hormones are biologically active chemical substances secreted by endocrine glands, and they play an important role in regulating physiological functions within the body. The synthesis of many hormones is closely related to amino acids. For example, the synthesis of thyroid hormones requires tyrosine (which is derived from phenylalanine in the body), and thyroid hormones regulate metabolism and promote growth and development. The synthesis of insulin also requires the participation of various amino acids. Insulin is a key hormone in regulating blood sugar levels and maintaining energy balance. Additionally, tryptophan is a precursor to serotonin and melatonin. Serotonin is involved in mood regulation and appetite control, while melatonin helps regulate the sleep cycle. The normal synthesis of these hormones depends on the supply of essential amino acids.
Enzymes are proteins that catalyze chemical reactions within living organisms, and they play a crucial role in cellular metabolism. The active sites of enzymes are typically composed of specific amino acids, and the types and sequence of these amino acids determine the enzyme's catalytic properties and efficiency. For instance, pepsin, a digestive enzyme, has an active site containing amino acids like aspartic acid, which catalyzes the hydrolysis of proteins to help the body break down dietary proteins and absorb nutrients. Essential amino acids, as components of enzymes, are indispensable for maintaining the structure and function of enzymes, thereby ensuring smooth cellular metabolism.
Animal-based foods are a high-quality source of protein, containing a rich supply of essential amino acids. Meats (such as beef, pork, and lamb) are not only high in protein content but also have an amino acid composition that closely matches the body's needs, making them easily digestible and absorbable. Poultry (such as chicken and duck) also provides abundant essential amino acids and is relatively low in fat, making it a good choice for a healthy diet. Fish and seafood not only provide essential amino acids but are also rich in unsaturated fatty acids, vitamins, and minerals, benefiting cardiovascular and brain health. Dairy products (such as milk and cheese) are good sources of easily absorbable essential amino acids, and their high calcium content supports bone health. Eggs (such as chicken and duck eggs) have excellent protein quality, with a balanced amino acid composition, making them an ideal food for supplementing essential amino acids.
Although the amino acid composition of proteins in most plant-based foods is not as complete as in animal-based foods, some plant-based foods are considered "complete proteins," meaning they contain all the essential amino acids. For example, quinoa is a highly nutritious grain that contains all essential amino acids in balanced proportions, making it an ideal choice for vegetarians to supplement essential amino acids. Soybeans and their products (such as tofu and soy milk) are also excellent sources of high-quality plant protein, rich in essential amino acids and free of cholesterol, suitable for all kinds of people. Buckwheat is another complete protein source, with a high content of essential amino acids, along with abundant dietary fiber and minerals, which are beneficial to health.
In dietary supplements, essential amino acids typically exist in the form of single amino acids or amino acid complexes, helping athletes enhance endurance and recovery, support older adults in maintaining muscle mass, and promote overall health. Essential amino acids are especially popular in fitness and sports nutrition, where they are widely used to improve athletic performance, accelerate muscle repair, and reduce muscle damage caused by exercise. Additionally, essential amino acids are often used to treat specific nutritional deficiencies and metabolic disorders.
Essential amino acids are widely used in the food industry to enhance the nutritional value and functional properties of food products. Lysine, methionine, and tryptophan, as common nutritional fortifiers, are added to infant formula, sports nutrition products, and specialized dietary items to balance the amino acid profile in diets. Additionally, essential amino acids serve as flavor enhancers and are used in the production of sweeteners (such as aspartame) and seasonings, imparting unique flavors to food. For medical foods and post-surgery recovery diets, amino acids play a vital role in supporting patients' health.
In the pharmaceutical and healthcare sector, essential amino acids are used as critical raw materials for drug manufacturing and functional dietary supplements . For example, valine and leucine are often utilized in the production of amino acid infusion solutions to alleviate metabolic disorders and accelerate recovery. Leucine, as part of branched-chain amino acids, is a key component in sports nutrition supplements , aiding in muscle recovery and immune enhancement. Tryptophan, as a precursor of serotonin, is important in the treatment of depression and anxiety, while methionine is utilized in developing drugs due to its antioxidant and liver-protective properties.
Essential amino acids play a crucial role in the animal feed industry. Lysine, methionine, and tryptophan are used as efficient feed additives to promote animal growth, improve feed conversion efficiency, and reduce nitrogen emissions. Supplementing these amino acids significantly enhances protein synthesis in poultry, pigs, and fish, boosting the yield and quality of meat, eggs, and dairy products, thereby driving efficiency in livestock production.
Due to their excellent moisturizing, antioxidant, and reparative properties, essential amino acids are widely applied in cosmetics and personal care products. Lysine and methionine promote collagen synthesis , enhancing skin elasticity and improving hydration. Methionine, as a component of hair keratin, is used in the development of hair care products designed to prevent breakage, repair damage, and strengthen hair. Furthermore, the antioxidant capacity of essential amino acids helps neutralize free radicals, delaying skin aging and making them key ingredients in anti-aging formulations.
In agriculture, essential amino acids are employed as plant growth regulators and amino acid-based fertilizers to promote crop growth, enhance stress resistance, and improve yield. For instance, lysine is often used to develop agrochemicals that boost plant health. In biotechnology, essential amino acids serve as nutrient substrates in fermentation processes, significantly enhancing the growth efficiency of industrial microorganisms, making them an integral part of modern biocatalysis technologies.
Essential amino acids exhibit great potential in the fields of chemicals and materials science due to their unique chemical structures. For example, lysine and other amino acids are commonly used as intermediates in the synthesis of chiral compounds for pharmaceuticals, agrochemicals, and functional materials. Lysine derivatives are also widely applied in the development of biodegradable polymers, particularly in tissue engineering and drug delivery , advancing the research and application of novel materials.
Amino acids are crucial to human health and functioning. They're not just the basic structure of proteins, they're also crucial for metabolism, immunity and control of the nervous system. Because the human body cannot produce these amino acids from itself, we must consume enough of them through a well-balanced diet to satisfy our physiological needs. The role of the essential amino acids not only informs the scientific development of healthy diets, but also informs developments in the complementary fields of dietary supplements, pharmaceuticals and functional foods. As science progresses, future understanding of the workings of essential amino acids will grow deeper and richer, thus increasing their ubiquity in health management and disease prevention.
