Why essential amino acids are not synthesized in the body

They include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. Arginine is conditionally essential; although you can synthesize it, during times of rapid growth you may not be able to make enough to keep up with your needs.

Non-essential amino acids, on the other hand, are not absolutely required in the foods you consume. However, your diet must still offer adequate total protein to maintain optimal health. Your body does not store excess dietary amino acids the way it does carbohydrates or fats, and a deficiency of even one essential amino acid can lead to health issues. Because you need protein for so many physiological functions, if your diet does not provide sufficient amounts of these nutrients, you will begin to degrade your muscle tissue so your cells can access the missing amino acid.

In addition, synthesis of non-essential amino acids can depend on the presence of adequate total dietary protein, as the amino acids it contains can serve as biological precursors. For example, you can synthesize tyrosine from excess phenylalanine or cysteine from excess methionine, but only if you have enough starting material to spare.

All food proteins that originate from animals contain the full complement of essential amino acids. Some commonly known hormones are Thyroid, Insulin, Adrenalin etc. One more important function of amino acids is to supply energy to the body. Typically, a healthy body on an average diet uses carbohydrates as a primary source of fuel but proteins and amino acids can be used as a last resort when the primary sources are depleted due to rigorous exercise.

Amino acids also play an important role in food taste. Proteins do not have much taste, but every amino acid has its own taste, and the combination of these is one of the important factors in defining food taste. Since our bodies cannot make all amino acids, we must consume some necessary amino acids through our diets from various foods.

A balanced diet complete with necessary amino acids is very important for proper function of body. Obtaining balanced nutrition is important for a healthy life. It is necessary to get 5 major nutrients proteins, fats and carbohydrates, plus vitamins and minerals in a balanced way. If this balance is broken such as any single nutrient is taken in excessively, the risk for obesity and lifestyle-related diseases increases. These are called the amino acids scoring patterns. If an amino acid is less than the amino acids scoring pattern, it is called the limiting amino acid.

The nutritional value of a protein can be improved by supplementing the limiting amino acid. Amino acid score is a numerical value showing how much the smallest limiting amino acid satisfies the scoring pattern.

It can be said that a protein with an amino acid score close to is good quality protein. In general, animal proteins such as eggs are good quality proteins with high amino acids scores. On the other hand, the scores of vegetable proteins such as wheat and corn are known to be low. For a healthy life, it is essential to eat a diet with a proper balance of good-quality proteins; namely, essential amino acids, which cannot be made by the body.

If amino acids are ingested in a proper balance, the body can effectively use them, and less waste will be excreted. A required daily intake is proposed for each of nine essential amino acids. Balance of essential amino acids in food is often illustrated as a wooden barrel that is used for filling water. Each board of the barrel represents each type of essential amino acid in food. A food with an ideal balance of amino acids, such as an egg, has a barrel with every board neatly forming a line at the same height.

In case of wheat, however, the boards are different in height. If any one of the boards is shorter than the others, you can only fill the barrel as high as the lowest board and the water beyond that runs out of the barrel.

Medical Physiology. Philadelphia, PA: Elsevier; chap Dietzen DJ. Amino acids, peptides, and proteins. In: Rifai N, ed. St Louis, MO: Elsevier; chap Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein and amino acids. J Am Diet Assoc. PMID: pubmed.