Proteins are large bio-molecules, or macro-molecules, consisting of one or more long chains of amino acid residues.Amino acids are the building blocks of proteins.These are organic compounds which contain at least one amino group (-NH2) and a carboxy (-COOH) group.
- Essential amino acids- Eight amino acids are essential for humans, as the body cannot produce them by themselves, and they have to be supplied externally (through diet). These are: isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine.
- Arginine and histidine form the group of so-called semi-essential amino acids.They have to be consumed in the diet under certain circumstances.
- Non-Essential amino acids- There are ten non-essential amino acids which are able to be produced in the body. The following amino acids fall into this category: alanine, asparagine, aspartic acid, cysteine, glutamine, glutamic acid, glycine, proline, serin and tyrosine.
Why do we need protein?
Repair and maintenance
Protein is vital in the maintenance of body tissue, including development and repair. Hair, skin, eyes, muscles and organs are all made from protein.
Protein is a major source of energy. If you consume more protein than you need for body tissue maintenance and other necessary functions, your body will use it for energy. If it is not needed due to sufficient intake of other energy sources such as carbohydrates, the protein will be used to create fat and becomes part of fat cells.
Protein is involved in the creation of some hormones. These substances help control body functions that involve the interaction of several organs. Insulin, a small protein, is an example of a hormone that regulates blood sugar.
Enzymes are proteins that increase the rate of chemical reactions in the body.
Transportation and storage of molecules
Protein is a major element in transportation of certain molecules. For example, haemoglobin is a protein that transports oxygen throughout the body. Protein is also sometimes used to store certain molecules. Ferritin is an example of a protein that combines with iron for storage in the liver.
Protein forms antibodies that help prevent infection, illness and disease. These proteins help in destroying antigens such as bacteria and viruses. They often work in conjunction with the other immune system cells.
A “complete” protein is one that contains all the essential amino acids that we humans need to survive.
How much protein do we actually need?
- The Recommended Dietary Allowance (RDA) of protein for adults leading a sedentary lifestyle is 0.8 g (apporx. 1 g) of protein per kilogram of body weight per day.
- The requirements of protein for individuals in a general fitness programme is as per the normal RDA values (given above).
- For competitive and more intense sports, athletes need to consume 1.5 g – 2.0 g of protein per kg body weight per day.
Calculate your recommended protein intake according to your goal and activity level using the calculator given below!