Protein as Diet

Mon, 07 Oct 2013 15:31:55 +0100

PROTEIN

Proteins are made up of amino acids that are essential for growth, maintenance and repair of body tissue and other vital processes. There are 20 amino acids, eight of which are said to be essential because you must get them directly from food. Foods from animal sources like meat, eggs, fish and dairy contain all eight essential amino acids and are said to be complete proteins. Plants contain some amino acids, but rarely contain all eight essential amino acids.

A protein is any chain of amino acids. An amino acid is a small molecule that acts as the building block of any protein. If you ignore the fat, your body is about 20-percent protein by weight. It is about 60-percent water. Most of the rest of your body is composed of minerals (for example, calcium in your bones).

Amino acids are called "amino acids" because they contain an amino group (NH₂) and a carboxyl group (COOH) that is acidic. In the figure above, you can see the chemical structure of two of the amino acids. You can see that the top part of each one is the same. That is true of all amino acids -- the little chain at the bottom (the H or the CH₃ in these two amino acids) is the only thing varying from one amino acid to the next. In some amino acids, the variable part can be quite large. The human body is constructed of 20 different amino acids (there are perhaps 100 different amino acids available in nature).

As far as your body is concerned there are two different types of amino acids: essential and non-essential. Non-essential amino acids are amino acids that your body can create out of other chemicals found in your body. Essential amino acids cannot be created, and therefore the only way to get them is through food. Here are the different amino acids:

Non-essential:

Alanine (synthesized from pyruvic acid)
Arginine (synthesized from glutamic acid)
Asparagine (synthesized from aspartic acid)
Aspartic acid (synthesized from oxaloacetic acid)
Cysteine (synthesized from homocysteine, which comes from methionine)
Glutamic acid (synthesized from oxoglutaric acid)
Glutamine (synthesized from glutamic acid)
Glycine (synthesized from serine and threonine)
Proline (synthesized from glutamic acid)
Serine (synthesized from glucose)
Tryosine (synthesized from phenylalanine)

Essential:

Histidine
Isoleucine
Leucine
Lysine
Methionine
Phenylalanine
Threonine
Tryptophan
Valine

Protein in our diets comes from both animal and vegetable sources. Most animal sources (meat, milk, eggs) provide what's called "complete protein", meaning that they contain all of the essential amino acids. Vegetable sources usually are low on or missing certain essential amino acids. For example, rice is low in isoleucine and lysine. However, different vegetable sources are deficient in different amino acids, and so by combining different foods you can get all of the essential amino acids throughout the course of the day. Some vegetable sources contain quite a bit of protein. Nuts, beans and soybeans are all high in protein. By combining them, you can get complete coverage of all essential amino acids.

But did you know that there are different types of fat?

Saturated fat is found in foods such as cheese, sausages, butter, cakes, biscuits and pies. It can raise your blood cholesterol level and increase your risk of heart disease. Most people in the UK eat too much saturated fat, which puts us at risk of health problems.

Unsaturated fats, on the other hand, can help to lower cholesterol and provide us with the essential fatty acids needed to help us stay healthy. Oily fish, nuts and seeds, avocados, olive oils and vegetable oils are sources of unsaturated fat.

Try to cut down on foods that are high in saturated fat and have smaller amounts of foods that are rich in unsaturated fat instead. For a healthy choice, use just a small amount of vegetable oil or reduced fat spread instead of butter, lard or ghee. When having meat, choose lean cuts and cut off any visible fat. Learn more in Eat less saturated fat.

The digestive system breaks all proteins down into their amino acids so that they can enter the bloodstream. Cells then use the amino acids as building blocks to build enzymes and structural proteins.