Amino Acids: The Science Behind the Labels

Amino Acids are the building blocks of life. They are found in all living organisms and play key roles in their metabolism, growth, development, reproduction and many other functions. Amino acids have been used since ancient times to make medicines such as antibiotics and vaccines. Today they are being studied for potential use in treating diseases including cancer, diabetes, heart disease and Alzheimer’s disease (AD).

The term “amino acid” refers to any molecule containing one or more amino acids. The most common ones include arginine, glycine, proline, glutamic acid and tryptophan. All these amino acids are essential for human health and survival. If not obtained from foods or dietary supplements, they must be synthesized in the body.

There are two main types of amino acids: Essential and Non-essential. Essential amino acids are those that cannot be produced in the body without supplementation. These include the B vitamins, thiamin, riboflavin and niacin. Non-essential amino acids are those that can be synthesized but do not contribute to healthy functioning of cells and tissues. Examples of non-essential amino acids include lysine, methionine and cysteine.

Besides being an important energy source, the body uses amino acids to create the structure of muscle and other tissue. They are also used in the creation of enzymes, hormones and various biologically active substances such as neurotransmitters, which are chemical messengers that brain cells use to communicate. Other amino acids help the body maintain proper water balance and pH levels in cells.

Amino acids are classified as either “essential” or “non-essential” based on whether they can be synthesized in the body or not. Essential amino acids must be consumed through diet, while non-essential amino acids can be created by the body from other compounds.

Amino acid composition of the 20 naturally occurring proteinogenic amino acids.

Amino Acids and the Nutrition Labels

Foods are required to list on their nutrition labels the amount of protein they contain in grams as measured by dried weight. This amount is found under a column labeled “Protein” and composed of individual listings for “Lectins”, “Minerals”, and “Vitamins”.

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The amount of essential and non-essential amino acids are also provided on this nutrition facts label. Dietary guidelines recommend that 10-35% of daily calories come from proteins. The daily value (%DV) for protein is set at 50 grams per day. This is, however, not based on individual needs but rather 2,000 calorie average diet and it can be consumed in one sitting or divided throughout the day (citation needed).

The Food and Drug Administration (FDA) states that there is no evidence that protein needs are increased in athletes beyond the recommended dietary allowance (RDA). However, many athletes and trainers recommend 1.5 to 2 times the RDA for athletes performing heavy exercise and 1.2 to 1.5 times the RDA for athletes involved in moderate exercise (citation needed).

When the amount of individual amino acids are listed on a nutrition facts label, it can be used to determine if the protein in a food is complete or incomplete.

Protein Quality

Proteins are also assessed for their quality. Protein quality is determined by comparing the essential amino acid content of a food protein with the essential amino acid needs of humans. The higher the protein quality of a food, the more complete it is as a source of protein.

There are six primary methods of assessing the quality of a given protein. These methods are:

Protein Efficiency Ratio (PER) – A method of assessing protein quality that compares the weight gain of experimental subjects fed a given protein with their weight gain when they are fed a standard casein protein.

Net Protein Utilization (NPU) – A measurement of the percentage of ingested protein that is absorbed and actually used by the body.

Biological Value (BV) – A measurement of the efficiency of protein utilization by the body.

Protein Digestibility Corrected Amino Acid Score (PDCAAS) – The current method of assessing a protein’s quality, this number is based on both the amino acid needs of humans and how well the protein in question meets those needs.

Protein Efficiency Ratio (PER) – A measurement of the growth rate of experimental subjects fed a given protein compared with that of subjects fed a standard casein protein.

FD are Essential Amino Acids, ND are Non-Essential Amino Acids

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Amino Acid Types and Functions

The human body uses twenty different amino acids to create proteins. The breakdown of these amino acids creates peptide chains, which in turn create the different proteins in the body. There are eight essential amino acids that the body cannot produce, and these must be provided to your diet. There are twelve other amino acids that can be created by the body. These are called non-essential amino acids.

The following is a list of the twenty different amino acids in alphabetical order:

Amino Acid Abbreviation Alanine Ala Arginine Arg Aspartic acid Asp Cysteine Cys Glutamic acid Glu Glycine Gly Histidine His Hydroxyproline Hypotheseine Hysz Leucine Leu Lysine Lys Methionine Met Phenylalanine Phe Proline Pro Selenocysteine Sec Serine Ser Th

Sources & references used in this article:

Racemic amino acids from the ultraviolet photolysis of interstellar ice analogues by MP Bernstein, JP Dworkin, SA Sandford, GW Cooper… – Nature, 2002 – nature.com

Measurement of local cerebral protein synthesis in vivo: influence of recycling of amino acids derived from protein degradation by CB Smith, GE Deibler, N Eng… – … of Sciences, 1988 – National Acad Sciences

A spirocyclohexyl nitroxide amino acid spin label for pulsed EPR distance measurements by A Rajca, D Velavan Kathirvelu, SK Roy… – … (Weinheim an der …, 2010 – ncbi.nlm.nih.gov

Bioorganometallic Chemistry ‐ Transition Metal Complexes with α‐Amino Acids and Peptides by K Severin, R Bergs, W Beck – … Chemie International Edition, 1998 – Wiley Online Library

Fluorinated amino acids: compatibility with native protein structures and effects on protein–protein interactions by M Salwiczek, EK Nyakatura, UIM Gerling… – Chemical Society …, 2012 – pubs.rsc.org