There are three basic forms of protein supplements. Intact proteins that have many amino acids joined together (polypeptides) are one source. These are usually available as casein (milk protein), whey (lactalbumin), egg protein (albumin), soy protein, or a combination. The advantage of intact proteins is that they are the closest to protein in nature.
The second option are hydrolysates, which are intact proteins broken down in an enzyme bath into two or three amino acid chains (dipeptides or tripe tides). The advantage of hydrolysates is that they are what the body makes when it takes in intact proteins. Studies show hydrolysates are better absorbed into the bloodstream. The body may better recognize hydrolysates, and hence, use them more readily.
Finally, there are the free-form amino acids that are derived from a special bacterial fermentation process. The advantage of free-form amino acids is that their combination is not fixed and can be determined by the user. Many manufacturers claim that free-form amino acids, requiring no digestion, are absorbed at a greater percentage and faster than pre-digested or peptide-bonded amino acids. (This has not been proven in the literature, as many studies show that hydrolysates are more bioavailable.) Another advantage is that as isolated amino acids they do not have the food characteristics and allergy potential associated with dairy byproducts.
The cheapest source of protein is food. As long as fat and calorie content are taken into consideration, protein should be acquired by food. Most Americans already consume adequate amounts of protein in their meat-rich diets. Cutting back on meat because of the fat content will usually not cause protein deficiencies. The recommended dietary allowances are not difficult to meet with a varied diet.
A varied diet with protein, fat, and carbohydrates is crucial. Protein alone (without carbohydrates or fat) will be used for energy as this is the body's first priority. Tissue building will be neglected. If the protein is not required for energy or tissue building it is broken down into the amino acids. The amino acids are then broken down in a process called deaminization, which converts the amino acids to glucose and glycogen and stores them in the liver to be used as energy. If their use for energy is not required they will be converted and stored as fat.
Look for products that contain complete proteins that have a good balance of amino acids.
Milk contains two complete proteins, casein and lactalbumin.
Beef, pork, poultry, and fish contain protein that is very similar in amino acid content to the amino acid requirements of humans. Fish compares favorably with meats and poultry as a good source of protein and may be lower in fat and cholesterol. Choose meats with the least fat to protein ratio.
Egg protein contains the essential amino acids in proportions that nearly mimic the ideal proportions required by humans. Eggs contain 13% protein, which is less than meat because of eggs' high water content.
Vegetables are poor sources of protein with the exception of legumes (the bean family). Soy beans have the highest protein content, followed by lima beans. Peanuts (which are really a legume) contain about 26% protein.
Breads and cereals contain between 7-14% protein but are generally low in one or more essential amino acids. For example, wheat is low in lysine, corn in Tryptophan, rice in Tryptophan, Cystine and methionine. Plant proteins, however, may supplement each other in such a way that a combination may provide a better balance of amino acids than any other food alone. Combining different protein sources will insure that all the amino acids are provided for your body's fuel.
Although the body manufacturers all the non-essential amino acids from the nine it receives through the diet, this does not mean it is making enough for all of its needs. A person who eats two eggs for breakfast, a hamburger for lunch, and a steak for dinner is getting more than enough protein from his or her diet. If this goes on for any length of time, he or she is probably overweight, and most likely not very active.
People who consciously watch their fat intake, are physically active, or on a special diet such as a vegetarian diet should be more concerned about their protein intake. As physical activity increases, so does protein requirement. The RDA for protein is based on sedentary individuals and equals approximately 0.36 grams per pound of body weight (0.8 grams per kilogram). This includes approximately 25% margin of error. This protein standard is based on out-of-date studies that include little research later than 1977. It is also geared more to the individual described in the previous paragraph.
An active adult will most likely require 0.6 grams per pound or 66% more than the RDA. An endurance athlete or body builder can require up to 0.9 grams per pound or 250% of the RDA. For a 170-pound person this will be 153 grams of protein per day.
The big problem with protein intake is that sedentary people consuming the typical American diet get too much protein. Athletes and dieters who do not pay attention to their protein intake probably get too little. Excess protein is not stored in the body as lean muscle, but is converted and stored as fat, or eliminated through increased urination. Inadequate protein intake will cause strength and muscle mass to decline.