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Proteins are macronutrients composed of amino acids, which involved in numerous biological processes, including growth, repair and maintenance of tissues, enzyme production, hormone synthesis, immune function, and transportation of molecules within the body.

1. Growth and repair: Proteins are the building blocks of tissues in the body, including muscles, organs, skin, hair, and nails. A constant supply of amino acids is crucial to support tissue growth and repair. During periods of growth, such as childhood, adolescence, and pregnancy, protein metabolism is particularly important for optimal development and tissue formation.
2. Enzyme and hormone production: Proteins play a vital role in the production of enzymes and hormones. Enzymes are essential for various biochemical reactions in the body, including digestion, metabolism, and energy production. Hormones act as chemical messengers that regulate numerous physiological processes such as mood, metabolism, growth, and reproduction.
3. Immune function: The immune system relies on proteins to defend the body against pathogens, infections, and diseases. Antibodies, which are proteins, help identify and neutralize harmful substances. Additionally, proteins are involved in the production of immune cells and signaling molecules that coordinate immune responses.
4. Transport and storage: Certain proteins act as carriers and transport molecules in the body. For example, hemoglobin transports oxygen in the blood, while lipoproteins transport lipids. Proteins also serve as storage molecules for essential nutrients and minerals, such as iron in ferritin or calcium in casein.
5. Energy production: While carbohydrates and fats are the body’s primary sources of energy, protein can also be used for energy production when necessary. During periods of insufficient carbohydrate intake or prolonged fasting, protein metabolism allows for the breakdown of proteins into amino acids, which can be converted into glucose through a process called gluconeogenesis. This glucose can then be used as an energy source.

Protein Requirements:

The recommended dietary allowance (RDA) for protein intake is 0.8 grams of protein per kilogram of body weight per day (g·kg−1·day−1) for healthy adults; while children aged 4–13 years and aged 14–18 years require 0.95 and 0.85 g·kg−1·day−1, respectively to support growth and development. Inadequate protein intake can lead to muscle wasting, impaired immune function, poor wound healing, and compromised organ function.

Protein Quality:

Protein can be obtained from two primary sources: animal proteins (such as meat, poultry, fish, eggs, and dairy) and plant proteins (including legumes, grains, nuts, beans, and peas). Animal proteins are considered “complete proteins” because they contain all the essential amino acids that the body requires. On the other hand, except for soybeans, plant proteins are considered “incomplete” as they often lack one or more essential amino acids. However, by combining different plant-based protein sources, one can obtain a complete amino acid profile.

To conclude, protein is vital for maintaining overall health and well-being. It is important to achieve a balanced protein intake from a variety of sources as part of a well-rounded and nutritious diet.

References:

1. Calder, P.C., Carr, A.C., Gombart, A.F., & Eggersdorfer, M. (2020). Optimal Nutritional Status for a Well-Functioning Immune System Is an Important Factor to Protect against Viral Infections. Nutrients, 12(4), 1181.
2. Berg, J.M., Tymoczko, J.L., Gatto, G.J. (2002). Stryer L. Biochemistry. 5th edition. New York: W H Freeman
3. Hudson JL, Baum JI, Diaz EC, Børsheim E. Dietary Protein Requirements in Children: Methods for Consideration. Nutrients. 2021 May 5;13(5):1554. doi: 10.3390/nu13051554. PMID: 34063030; PMCID: PMC8147948.