What is Protein? Good Sources of Protein

Protein is composed of nitrogen containing compounds called amino acids. These amino acids will bond to each other to form what biochemists call peptide polymers, which in turn will form particular proteins. The sequence of amino acids in the peptide polymer will determine the nature of the protein, and there are many different kinds of proteins.

Proteins may be used to form new bodily tissue, e.g.muscle, bone, teeth, skin, and nervous tissue, as well as enzymes and globulins necessary for maintaining life.

There are twenty two amino acids, eight of which are termed essential amino acids, meaning that these eight have to be supplied by the diet. The other amino acids may be synthesized by the body from other nonessential amino acids.

Foods containing all eight of these essential amino acids are termed complete proteins. Those lacking one or more of the essential aminos are termed incomplete proteins. The relative proportion of amino acids compared to those found in human tissue, as well as the degree of assimilability will determine the biological value and protein efficiency ratio of a particular protein. For example, while both soybeans and milk contain complete proteins, milk proteins such as whey, casein, and lactalbumin will have a higher biological value.

Gelatin, for example, while classified as a protein, lacks the essential amino acid tryptophan, thereby making gelatin useless as a protein unless enough tryptophan is supplied to make it assimilable. Rated according to their biological value are the following:

Egg
Milk
Meat
Fish
Soy
Peanut
Wheat gluten

Those choosing to follow a strict vegetarian, vegan regimen will need to combine incomplete proteins to balance out the amino acid profile. For example, two incomplete proteins such as rice and beans may be combined to form a complete protein. It is definitely possible to be healthy and fit as a vegetarian, but it does require a bit more planning.

Severe protein deficiency is rare. The medical term for this is kwashiorkor and is usually seen only in developing or politically unstable areas of the globe. Symptoms include a swollen, distended abdomen, bulging eyes, and wasting musculature. The protein status of an individual may be determined by something called nitrogen balance. If more nitrogen is leaving the body via the urine than has been ingested via the diet, the patient is said to be in negative nitrogen balance, a wasting condition common to many forms of illness. Someone taking in more nitrogen than is being excreted is considered to be in positive nitrogen balance and probably gaining lean body mass via a program of resistance exercise and improved nutrition. Most of the time we are likely to be in nitrogen equilibrium, neither gaining or losing lean body mass.

Good Sources of Protein

Minimum protein requirement is approximately 0.8 grams of protein per kilogram of bodyweight.

Put in more simple terms, a 220lb person would require 80 grams of protein per day. This is a minimum requirement needed to be in nitrogen equilibrium. Pregnancy, lactation, active growth, or the use of anabolic drugs, etc. may substantially increase one’s requirement. Usually it is suggested that protein make up about 15 to 20% of one’s total calorie intake. Too much protein above and beyond an individual’s needs will be converted and stored as fat if the total calorie intake is beyond that person’s immediated needs. While protein can be used to provide energy, it is an inefficient source. Protein provides 4 Kcal. of energy per gram.