Protein has been in the news a lot.A high protein diet has been advocated by some for weight loss. Personal commentaries suggest that it works for some people. Other's debate that there are no scientific studies to prove this and in the longterm there will be a negative impact on health!! Except fats all foods contain some amount of protein, let us look at what these protiens are.

What are Proteins?

Types of Amino Acids: There are two types of amino acids. The amino acids that our bodies cannot manufacture are called essential amino acids. These (nine)have to come from our diets. The others can be synthesised in our body(11) and are called nonessential amino acids.

Sources of Protein: Protein is present both in plant foods and animal foods. Plants have a unque ability to "fix" nitrogen from the soil with a carbon atom. Virtually all the amino acids are made from scratch only by plants. So you can see why one can be a vegetarian and still meet the protein requirements! However the availability quality, and biological value of these plant proteins is much lower than the animal protein.

Functions of Protein: Almost all cells in the body are made up of protein. It is therefore a vital nutrient. In addition proteins have distinct functions that they perform.
Body Structure- muscle tissue, of the muscle, the heart connective tissue, tissue that supports bones, etc.

Fluid Balance:
The blood proteins(albumin, and globulin) help maintain fluid balance.
Acid Base balance: Proteins help to regulate the amount of free hydrogen ions. This helps to keep our blood pH fairly constant(pH7.35 to 7.45).
Hormones and Enzymes: Many hormones like, thyroid, insulin are referred to as peptide hormones. These regulate our metabolisn and blood sugar. Diabetics who take insulin cannot take it orally as this "protein" will get broken down into amino acids and will be ineffective for lowering blood sugar. Most of the enzymes are proteins.Enzymes help in metabolic activity of the body. eg. a child suffering from Galactosemia, lacks the enzyme galactase that metabolises the sugar galactose. This child will have to be put on a galactose free diet tp prevent growth and mental retardation.
Immune Function:The key parts of the immune system are proteins. Antobodies which are produced by our body in response to a foreign body(virus, bacteria, etc) are proteins. In patients with infection, like AIDS this immune response is reduced. Women who are pregnant also have a lower immunity, are more susceptible to infections(remember the sperm is a foreign body to the woman's body!), but this is normal so as to ensure the survival of the fetus!!. Lack of hygiene and public health were there the reasons for increased mortality seen in women during the early 20th century.
Glucose Formation:
The body likes to use carbohydrate as its main fuel. The brain is totally dependent on glucose, (carbohydrates are broken down to give the sugar glucose in our body) and 35% of all the energy when we are resting is used by the brain. The body can use proteins to make glucose. eg. If you skip breakfast and havent eaten since the last meal at 6p.m the day before. Each gram of protein gives 4 calories of energy. Most high protein foods also contain some amount of carbohydrates.

How much Protein do we need ?Infants have the highest requirement of protein as they are growing rapidly. Children need amuch higher amount of protein than adults as they need to grow their muscle, and cells in the body,in addition to repair, and maintenance of their tissues.An adult weighing 154 lbs (70 kg) needs 56grams of protein and a woman weighing 120lbs (55 kg) needs 44grams of protein. In the US men eat 105 grams/day and women 65grams/day.

Is too much protein harmful? There is research to indicate that habitual consumption of a high animal protein based diet has an effect on health. Sudies suggest that high red meat intake has been linked to colonic cancer, and to heart disease. However it is very difficult to separate out if it is the protein in the meat alone or is ir the high fat associated with red meat intake that is the cause. There is also concern that the kidneys are taxed to excerete nitrogen in excess. This is particularly relevant to people with diabetes,or kidney diseases. It is better to keep the intake of protein to the recommended level, and introduce plant proteins like beans, and lentils that have beneficial effects on health.