Protein is an organic compound containing carbon, hydrogen, oxygen and nitrogen. The smallest unit of protein is AMINO ACID; when we eat protein it is broken down by our body during digestion to amino acids.
The origin of amino acid is plant, plants synthesise amino acids from carbon dioxide, water and nitrogen obtained from soil or in some cases from the air; this is followed by combining several amino acids to form protein. Animals get protein when they eat plants while man gets protein when he eats plants and /or animals.
There are 20 amino Acids, out of which 9 are essential (cannot be manufactured by the body) and thus must be gotten from foods eaten while the other 11 are non-essential (can be manufactured by the body) using nitrogen obtained from other amino acids.
The body combines the various amino acids to form proteins; two types of proteins are formed:- fibrous protein and globular proteins. The fibrous protein is strong mechanically and makes up the muscles, hair, nails and connective tissue; the globular protein which is water soluble is found within the cells and constitute the hormones, antibodies, enzymes and body fluid.
Functions of protein include body building (growth), provision of energy, formation of hormones, antibodies, enzymes and body fluids. Proteins also help in the transportation of certain substances in the body.
As said earlier, there are a total of 20 amino acids required by the body to manufacture protein; 9 are essential while 11 are non-essential. Animal and plant proteins differ a great deal; animal protein contains all 9 essential amino acids in enough amounts whereas plant proteins are low in one or more of the 9 essential amino acids; the only plant protein that has all the 9 amino acids in required quantities is SOYBEAN.
If just one essential amino acid is absent in the body, protein cannot be produced; consequently the other amino acids will be used up as energy OR converted to carbohydrate or fat and stored in the body for future energy needs.
Sources of high quality protein include meat, eggs, dairy products, fish and soybeans.
1. White meat
White meat is meat from chicken, turkey and other birds; it is a rich source of high quality protein. It does not have haem which erodes the lining of the intestines and does not have the saturated fat of red meat. It has not been incriminated in bowel cancer and heart disease.
However, cholesterol is contained chicken, turkey and so on. However, the skin of poultry is most high in cholesterol, consequently, chicken should be skinned (that is, remove the skin) before eating it. This is not easy but we must discipline ourselves because the skin is quite delicious.
2. Red meat
Red meat which could be pork (from pigs), beef (from cows, bulls and mature sheep/ram) or lamb (from young sheep) is a source of high quality protein. However red meat has some drawbacks; it has saturated fat in-between its fibres, red meat contains haem which gives it its colour and is said to cause erosion of the lining of the bowel; it is incriminated in bowel cancer and heart disease.
Besides; processing of red meat can result in production of carcinogens (cancer forming substances); processed meat is red meat preserved by curing, smoking, salting or preservatives. According to a large study carried out some years back, about one in every thirty early deaths is due to processed meat.
The World health Organisation International Agency for research on Cancer has classified processed meat as carcinogenic to human just like asbestos, alcohol, arsenic and cigarette.
Therefore, while red meat is a source of high quality protein; the World Cancer Research Fund has advised limitation of red meat consumption to 500g (0.5kg) ((cooked) and 700g (uncooked) per week.
3. Fish
Fish is a major source of high quality protein in our diet. In the riverine areas of our country it is the main source of protein. At a time in this country it was the cheapest source of protein; okweko, kote, or simply ice-fish was well known. Though there may be no scientific basis for this; people who live along the river side tend to have healthier weight than those upland and to an extent, healthier skin. Like I said it may just be an observation that has not been subjected to scientific challenge.
However, fish apart from being a provider of protein which is essential for growth and development, contributes immensely to our health because it has a lot of other nutrients such as omega-3 fatty acids, vitamins (D and B2) and minerals such as calcium, phosphorus and potassium.
Not every fish is good, some contain mercury as a contaminant which is not good for consumption. The good ones are the oily ones like sardines, salmon, kote, icefish etc.
4. Dairy products
A dairy product is any food made from milk of mammals like cows, sheep, goats and camels. These include various types of milk, butter, cheese, yogurt, and ice creams. They are very rich sources of high quality protein; all the nine essential amino acids are present.
However we must take note of at least two things: lactose in milk; this is a carbohydrate produced by mammals to which some persons are intolerant. Milk also contains fat (saturated fat), but this can be removed or reduced; you are therefore advised to go for fat-free milk or low-fat milk.
5. Eggs
Eggs are rich in protein, fat and micronutrients. The egg has two parts; the white part and the yolk (yellow part). The white is very rich in protein while the yellow part called the yolk is very rich in cholesterol; the latter (cholesterol) is worsened by frying the egg, as some cooking oils also contain cholesterol.
Eggs contain all nine essential amino acids in the required quantities besides minerals and vitamins.
In adults about two eggs a week will do but as we age this should reduce.
6. Soybeans
Plant proteins are of low quality,; they may have all the nine essential amino acids or some of them and in insufficient amounts. Thus one needs to consume a wide variety of plants to get all the nine essential amino acids in sufficient quantities.
However; one plant that has all the nine essential amino acids in sufficient quantities is SOYBEAN.
It is therefore a source of high quality protein; in fact the only plant source.
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