Introduction
Proteins come from the Greek word "Proteios", meaning 'of prime importance'.
Protein is the basic structural substance of the cell, forming bone, skin,
muscle, hormones, enzymes (proteins that help activate energy release),
haemoglobin, and platelets (a type of blood cell that is important in
blood clotting).
When eaten, proteins are broken down into amino acids (like carbohydrates
are broken down into glycogen), which link into chains to form new tissue
structures vital for life in the body. There are 20 amino acids, eight
(9 in young children and stressed older adults) of which cannot be synthesised
by the body and therefore must be provided preformed in foods that we
eat. These are called the eight 'essential amino acids'; the others manufactured
in the body are termed nonessential. There is no benefit in specific amino
acids from an animal origin compared to the same amino acid from a vegetable
origin.
There are fundamentally two types of protein; complete protein and incomplete protein. Complete proteins contain all 8 of the essential amino acids whereas an incomplete protein lacks one or more of the essential amino acids.
Hence a protein nutrient that contain all of the essential amino acids in terms of quantity and in the correct ratio to maintain nitrogen balance, and allow time for growth and repair are known as 'Complete Proteins'.
Sources of complete proteins include
The mixture of essential amino acids present in eggs is said to be the best among food sources and are often used as the benchmark in which to measure the quality and content of other sources of protein as shown in the table below.
| Source | |
| Eggs | 100 |
| Fish | 70 |
| Lean Beef | 69 |
| Cows Milk | 60 |
| Brown Rice | 57 |
| White Rice | 56 |
| Wholegrain Wheat | 44 |
| Peanuts | 43 |
| White Potato | 34 |
The table above is not suggesting that these food sources contain the highest amount of protein per serving. It is suggesting how they compare to eggs in providing essential amino acids.
Examples of protein content of food sources
| Source | Protein (g) |
| 4 oz Red meat | 32g |
| 6 oz Chicken | 38g |
| 1 Serving Prolab Whey | 22g |
| Pint of milk | 20g |
| 4 oz Tuna | 25g |
| 6 oz White Fish | 30g |
| 1 2XL Protein bar | 17g |
| 1 Carton of yoghurt | 8g |
| 2 oz Nuts | 13g |
| 2 Slices of bread | 6g |
| 2 oz Cheddar | 14g |
| Small tin baked beans | 10g |
| 4 oz Cottage cheese | 15g |
Further Reading : -
The relationship between Protein
and exercise
Calculation of Protein intake depending
on exercise levels
Protein supplementation