What is protein?

 

Protein is a material made up of amino acids. Protein is found in all living things (contrary to popular belief, meat isn't the only protein!), although the exact composition of that protein varies depending on the source. The variance between different types of protein and indeed the nutritional value of that protein is derived from the combination of the amino acid building blocks that it is made up of. On this page, I'll try to describe a little bit about protein, and about the amino acids that make it up.

 

Sources of protein and the concept of the limiting amino acid

Most of what we know about protein has been determined by research on domesticated animals and their diets. Farmers and agricultural researchers determined early on that different animal feeds produced different growth rates in livestock, and that the nature of the amino acid combinations in foodstuffs were the basis of the differing results. It was discovered that the absence of certain amino acids was lethal; we call this group of amino acids essential (The essential amino acids are tryptophan, lysine, methionine, phenylalanine, threonine, valine, leucine and isoleucine.). This means that they must be eaten in the diet. Later, the concept of the limiting amino acid was found where adding an amino acid that was missing from the foodstuff improved its nutritional value, up to a certain supplementation amount, above which no further improvement was found without the additional of another amino acid etc., up to a specific number of compounds. In essence, this meant that a mixture of amino acids was required to be in the diet, and that there was an optimum amount for each of those amino acids in the mixture. Not all of these amino acids was essential. Some were non-essential, meaning that they could be manufactured in the body (The non-essentialamino acids are tyrosine, glycine, serine, glutamic acid, aspartic acid, taurine, cystine, proline, and alanine.). Others were semi-essential, meaning that under certain circumstances, they could not be adequately produced by the body and had to be taken in the diet. (Arginine and histidine are considered semi-essential, particularly in the infant diet.)

 

Animal products (meat, fish, eggs, milk) and soybeans contain all the essential amino acids and are known as complete proteins. Incomplete proteins are foods which are low in some amino acids. Eating only incomplete proteins can result in deficiency of certain amino acids over the long term. For example, legumes are low in (limited by) methionine and tryptophan, but high in lysine and isoleucine and grains are high in lysine and isoleucine and low in (limited by) tryptophan and methionine. If you eat a food from each of these groups together, you can be relatively assured that you are getting a complete amino acid range or complete protein.

 

This is one of the reasons why beans and rice are traditionally eaten together, and if you live in the UK, you eat beans on toast!

 

It poses a more significant problems for persons on a vegan diet. Vegans should always consult reputable information sources to ensure that they are eating a balanced protein diet.

 

It's recommended that the average healthy person eat approximately .6 grams of protein per kilogram of body weight. To figure out the right amount for you, use the following equations:

Your weight in pounds / 2.2 = Your weight in kilograms.

Your weight in kilograms X .6 = Your recommended protein per day.

 

Here is a list of protein sources:

(Please note that the fat content is also given. If you are interested in restricting the quantity of fat in your diet you will want to choose the leaner protein sources.)

 

 

Supplements

Because of the imbalance that can result, supplementing a single amino acid for a long period of time is not advisable. This imbalance results from the displacement of similar amino acids to the one you are taking. Naturopaths recommend that single amino acid supplements be taken for no more than two to four weeks for a therapeutic use, and that complete protein sources be taken alongside the supplement.

 

Uses of some of the amino acids

Branched chain amino acids

The branched-chain amino acids, isoleucine, leucine, and valine have been used as supplements for muscle building. Arginine is also used for this purpose. Leucine has also been used to help heal wounds of the skin and bones.

 

Lysine

Lysine is used to prevent and treat Herpes simplex virus infections. It seems to be more effective for cold sores (herpes type 1) than for genital herpes (type 2). A typical dosage regime is 500 mg three times per day during an infection and 500 mg per day when there are no symptoms.

Phenylalanine

Phenylalanine is used to treat depression, musculoskeletal disorders and various types of pain including back pain, neck pain, osteoarthritis, rheumatoid arthritis, menstrual pain and headaches.

Tryptophan

Tryptophan supplements have been used to treat insomnia and depression.

Histidine

Histidine is used to treat allergies, ulcers, anemia, arthritis and high blood pressure.

 

Nonessential amino acids

Aspartic acid has been used to treat fatigue and depression. Glutamic acid has been used to treat fatigue and alcoholism. Cysteine can be converted to glutathione, which has antioxidant properties and it may be useful in preventing and treating disorders in which free radical damage plays a part. Tyrosine has also been used to treat depression.