Essential and non-essential amino acids: differences and roles

Amino acids are the building blocks of many elements in the human body, including proteins, hormones, enzymes, and neurotransmitters. All amino acids have a basic structure consisting of an amine group, a carboxyl group, a hydrogen atom, and an R group around a central carbon atom. It is the R group that distinguishes one amino acid from another. Sometimes called a side chain, the R group has a number of different properties based on polarity, charge, size, and solubility.

Thanks to these properties, the 20 amino acids can be divided into nonpolar, polar amino acids with a neutral charge, and negatively and positively charged amino acids. Amino acids can also be classified based on their ability to be synthesized by the human body. This is because while our bodies can manufacture nonessential amino acids, essential amino acids must be obtained from our diet, because our bodies are unable to produce them.

There are 11 non-essential amino acids and 9 essential amino acids. Non-essential amino acids can be produced using genetic material already present in the body's cells. However, the production of essential amino acids requires long and energy-dense pathways. The energy costs associated with producing essential amino acids eventually led to the loss of this genetic material in humans during our evolution.

The distinction between nonessential and essential amino acids was discovered through nutritional studies conducted in the early twentieth century. When essential amino acids are removed from the diet, the body's growth and nitrogen balance are negatively affected. In extreme cases, a deficiency of essential amino acids in the diet can lead to disorders such as kwashiorkor and marasmus. These two diseases are due to malnutrition and deficiency of essential amino acids.

In this article, I suggest you study the differences between essential and non-essential amino acids, as well as the dietary sources of these amino acids.

Non-essential amino acids

Non-essential amino acids are produced in the human body. Current research suggests that our bodies have retained the ability to produce these non-essential amino acids because they are essential for our survival and metabolic needs. The 11 non-essential amino acids include:

Non-essential amino acids perform various functions in the human body. For example, some non-essential amino acids such as glutamine and arginine can regulate gene expression and cell signaling pathways, respectively. Other non-essential amino acids help regulate digestion and absorption of nutrients. Serine and glycine are nonessential amino acids that facilitate the digestion and absorption of fats, or lipids, for example.

Essential amino acids

Essential amino acids are those that the human body cannot produce and must find in its diet. The nine essential amino acids are:

• Histidine.
• Isoleucine.
• Lucine.
• Lysine.
• Methionine.
• phenylalanine;
• Threonine.
• Tryptophan.
• Faline.

Essential amino acids, like their non-essential counterparts, perform several functions in the human body. These functions include the production of proteins, enzymes and hormones, as well as the regulation of various aspects of metabolism and gene expression.

Because arginine is a non-essential amino acid, its importance is generally discussed only during periods of recovery from illness or injury. During childhood, arginine also promotes growth hormone production, which can affect children's growth curve. Although children are able to synthesize their own arginine, children sometimes need supplements to correct developmental delays or to promote rapid growth spurts. This is why arginine is sometimes referred to as “nearly essential” during childhood.

Food sources of essential amino acids

Since essential amino acid requirements must be met through diet, researchers have established guidelines for consuming appropriate amounts of protein based on age, gender and health status. Based on data from public health studies, researchers recommend consuming at least 0.8 grams of protein per kilogram of body weight. However, certain groups of people, such as pregnant or breastfeeding women, often need to eat higher amounts of protein. When people are not able to consume enough foods that contain all nine essential amino acids, the body has difficulty producing the proteins it needs to function properly.

Dietary protein sources fall into two broad categories: complete proteins and incomplete proteins.

Complete proteins contain all nine essential amino acids, while incomplete proteins lack one or more of these amino acids. Complete proteins are found in a variety of food sources, such as meat, milk, eggs, and soy products. In Western countries, many people get their complete protein from these sources.

Although animal products provide all the essential amino acids that humans need, foods such as meat and dairy products often lack fiber and micronutrients, which are also essential for good human health. Therefore, health professionals recommend consuming as many essential amino acids as possible from plant sources.

Although many fruits and vegetables do not contain all essential amino acids, mixing different plant sources can provide individuals with all the amino acids the body needs to function properly.