Proteins: The Most Important Macronutrient
The major nutrients for all living things are proteins, fats and carbohydrates. Proteins are the most abundant. Skin, all 3 different kinds of muscle tissue, bone matrix, connective tissue, enzymes, hair, transport and immune systems are examples of mammalian organs that contain large amounts of protein.
It is easy to say that protein is the most important nutrient. It is also easy to say that without the unique utilization of proteins, fats and carbohydrates endowed by our Creator we wouldn't have life.
Enzymes are the large protein molecules that catalyze the chemical transformations in all living things. Enzymes break down foodstuffs into component parts in the digestive system.
Proteins are hydrolyzed, or broken down, into amino acids which are then transported to various parts of the body according to need.
Because of the unique characteristics of enzymes, the digestion process takes place at body temperatures under very mild conditions.
In the cells enzymes catalyze the synthesis of the unique proteins needed by the organism from the amino acids supplied. If the right amino acids are not present protein synthesis does not take place.
Proteins consist of carbon, hydrogen, oxygen, nitrogen, and small amounts of sulfur. Humans and animals can make glucose from amino acids, but cannot reverse the process.
When excess amino acids are needed for other things such as glucose, the amine group, containing the nitrogen, is removed and converted to ammonia. Ammonia, which is toxic to mammalian organisms, is converted into urea for excretion from the body.
The nitrogen in amino acids has to come from certain bacteria which are the only organisms that can take nitrogen from the air and turn it into ammonia. Plants utilize ammonia to make amino acids.
Plant and Mammalian Protein Differences
Plants make their own proteins which are quite different from animal and human proteins. Apparently plants make their own proteins from about 40 naturally occurring amino acids.
Mammalians use 20 different amino acids. The same 20 different amino acids are used in all mammalian species.
Plants are poor sources of protein for humans. Animals, some of which use microorganisms in their digestive process, are much better adapted to select the right amino acids, discard, break down and eliminate the amino acids that are not needed in humans.
There is a great deal of difference in the form and function of plant or mammalian proteins. Plants do not need to transport gases through out the plant structure. Carbon dioxide is fixed in the leaves and converted into sucrose which is then transported to stems and roots without the use of a central pump.
The first paragraph has a list of mammalian proteins, of which many, donít have counterparts in plants.
Plants donít have a blood transport system with unique cells that identify molecules or cells as friend or foe. Mammalian cells donít have cell walls as plants do.
The difference in form and function means there are quite different proteins with unique amino acid compositions. This translates into varying usefulness of plant proteins as sources for mammalian proteins.
Early nutritionists recognized that certain protein sources had to be fed in greater amounts to provide optimum growth of their test animals.
They found that animal sources such as beef liver, beef muscle, and eggs were more than twice as effective as plant sources in providing for optimum growth of their test animals.
This research data is ignored by those who claim that one protein is as good as another. The data also explain why vegetarians have to use a wide variety of vegetable sources to meet their amino acid requirements.
Some Continue to Insist on Limited Proteins Diets
Some mammalian proteins are recycled or replaced as often as every few minutes depending on their function. There should be no argument of the need for quality protein supply in the diet.
Yet many, such as the AHA, NHLBI, FDA, and allied nutritionists continue to proclaim that protein, especially that from red meat, be limited in the diet.
The reasoning apparently is that,according to them, saturated fat, and cholesterol, which accompanies red meat, is the cause of heart disease.
It has been shown that cholesterol and saturated fats are not the cause of heart disease. High cholesterol is the result of long time abuse of carbohydrates, particularly sucrose and fructose.
These sugars heavily used, or abused, over time result in heart disease. And this well established research is ignored by the proponents of the saturated fat-cholesterol cause of heart disease.
Other pages deal with the importance of cholesterol and saturated fat in humans.
In some cases, particularly in low calorie diets, inadequate protein and saturated fat intake will cause serious damage to the human body resulting in many of the modern nutritional diseases.
Supporting the content of this page are biochemistry text books and The Modern Nutritional Diseases by Fred and Alice Ottoboni.
The Importance of butter in human nutritional health is shown here. A new window will open
A primer on fats and fatty acids is here. A new window will open.
Home Page where nutritional diseases are defined.
The relationship between carbohydrates and fats in blood cholesterol levels is shown here. A new window will open.