Proteins and Amino Acids – The Body’s Building Blocks

What are Proteins ?

There are many misconceptions about and poor understanding of the function of Proteins in the Human Body.

Brain cells, muscle, skin, hair and nails are just some of the body parts that are protein based. Estimates suggest that about half of the human body’s dry weight is made up of protein.  Many of the foods we eat contain protein,  particularly flesh foods ( chicken, beef, lamb & fish) and legumes like beans and lentils. These proteins are digested to release amino acids. In the body these amino acids are used to make new proteins.

Amino Acids are the body’s building blocks. These  amino acids are joined together into long molecules called polypeptides. Each polypeptide has a very specific sequence of amino acids.

 

The Different Amino Acids

There are about 20 different amino acids, divided into two broad classes:

  • Those that can be made by the human body – Non-essential amino acids
  • Those that can only be supplied in food – Essential amino acids
Essential Amino Acids Nonessential Amino Acids
Histidine Alanine
Isoleucine Arginine
Leucine Aspartic Acid
Lysine Cysteine
Methionine Cystine
Phenylalanine Glutamic Acid
Tryptophan Glutamine
Valine Glycine
Threonine Proline
Serine
Tyrosine

 

The ultimate value of a food protein or protein supplement is in its amino-acid composition, particularly how many of the essential amino acids it provides and in what quantity. Different foods contain different numbers and amounts of amino acids. Generally speaking:

  • Animal products contain all of the essential amino acids.
  • Plant proteins usually lack at least one essential  amino acid. An exception to this is Soy products

Why is Protein Important ?

  • Protein is necessary for the building and repair of muscle and body tissues. Proteins are created constantly. For example as old dead skin cells are sloughed off , new ones are produced to replace them
  • It produces enzymes, hormones, and other substances the body uses. Examples of this are the brain chemical (neurotransmitter) Serotonin and the ” fight or flight ” chemical Adrenalin.
  • It regulates body processes, such as water balancing, transporting nutrients, and making muscles contract.
  • Protein keeps the body healthy by resisting diseases that are common to malnourished people. The body can’t store protein, so it must be supplied on a daily basis from the foods we eat.
  • Prevents one from becoming easily fatigued by producing stamina and energy. Although carbohydrates are the body’s preferred source of fuel, about 10% of energy is derived from protein

How much Protein do we need each day?

The daily protein requirement depends on several factors: weight , age and health. As a rough guide, the recommended daily intake for proteins measured in grams per kilogram of body weight is:

  • 0.75g/Kg for adult women
  • 0.84/kg for adult men
  • Around 1g/Kg for pregnant and breast-feeding women and for men and women over 70 years
  • The needs of children and adolescents also vary according to their age and weight

The following are the recommended serving sizes for protein:

  • 2 to 3 ounces of cooked lean meat, poultry, or fish (a portion about the size of a deck of playing cards)food_pyramid_adam
  • 1/2 cup of cooked dried beans
  • 1 egg, 2 tablespoons of peanut butter, or 1 ounce of cheese

Select  lean meat, poultry without skin, fish, and dried beans, and low-fat or fat-free dairy products often. These are the protein choices that are the lowest in fat. For more information, see the food guide pyramid

Vegetarians can solve their dietary problem by eating a combination of plant foods. For example, a meal containing cereals and legumes provides all the essential amino-acids found in a typical meat meal.

 

Rather than concentrating on proper nutrition, exercise, rest and relaxation many  turn to all sorts of Dietary supplements particularly high protein supplements to achieve their goals. This is due to many misconceptions about and poor understanding of the function of Proteins in the Human Body.

Some weight-trainers and bodybuilder believe that high protein diets lead to increased muscle mass. This isn’t true – it is stimulation of muscle tissue through exercise, not extra dietary protein that leads to muscle growth. Studies have shown that weight trainers who don’t eat extra protein still gain at the same rate as weight trainers who do supplement their diets with added protein

Fad diets that favour very high protein and fat intake, combined with very low carbohydrate intake, may be harmful.

A very high protein diet places extra strain on the kidneys and liver because they have to detoxify and eliminate unusually high quantities of protein by products. The body normally relies on carbohydrates as its energy source.  If the  body does not receive enough dietary carbohydrate it will break down muscle to make glucose. This results in muscle wastage and the build up of substances called Ketones.

I hope this article has helped you in your understanding of Proteins, their function and  their  importance in our diet

Watch for my next blog about  Carbohydrates

Doctor Bill