All to often you may hear bodybuilders and bodybulding magazines talking about protein intake. What you may hear a little less of and be somewhat unfamiliar with is the reference of achieving a “positive nitrogen balance” within the body. This mysterious phrase all too often goes without definition. So in an effort to more clearly define just what it exactly means to be (or not to be) in a positive nitrogen state, I have cited material from Arnold Schwarzenegger’s Encyclopedia of Modern BodyBuilding (I have said many times before, you need this book!! See my previous post on this book for more information on pricing and how to obtain your own book).
This is straight out of the book word for word from page 706. I scanned a copy of page 707 so the charts can be utilized for referencing.
“Protein is used by the body to build, repair, and maintain muscle tissue. As we’ll see, in this area bodybuilders have been way ahead of most nutritional experts in recognizing that building muscle (in fact, hard training of all sorts) requires a lot more protein intake thatn had been formerly realized.
The body cannot use the protein you ingest for muscle-building unless all of the necessary amino acids are present. However, the body itself can produce only some of these amino acids. The other, called the essential amino acids, have to be obtained from the foods you eat.
Protein is made up of carbon, hydrogen, and oxygen (as are the other macronutrients) and one more element none of the other nutrients have—-nitrogen. If you ever hear somebody talking about being in a positive nitrogen balance or negative nitrogen balance what they are referring to is whether they are in an anabolic state–able to build muscle–or in a catabolic one–losing muscle.
Some foods contain what is called complete protein–that is, they provide all the amino acids necessary to produce usable protein. Examples of these foods are milk, eggs, meat, fish, and various vegetable products, such as soybeans. But even these foods contain differing amounts of usable protein per weight. That is, even though a food might contain, say, 10 grams of protein, your body is able to use only a certain percentage of it–for example, only 7 or 8.5 grams.
Following (image below) is a chart that shows on the left what percentage protein makes up of various foods commonly used as protein sources and on the right what percentage of that protein your body is actually able to use for building muscle.
Click on the image to enlarge content for reading:
I think it is necessary to take note of the fact that whole eggs are the the food with the highest protein absorption rating….above fish, beef, chicken and any vegetable.
Because food protein absorption rating varies from food to food, it is important to mix your protein sources in any given meal to diversify the protein profile. An example would be to eat beef with a side of beans. This would provide you with two totally different protein profiles that will in turn result in greater protein absorption through the completed combination of amino acids available from both protein sources.
In his book The BodyBulder’s Nutrition Book, Franco Columbu addresses the subject of complete and incomplete protein sources and the utilization of protein from food.
He states, “All protein foods are not equally efficient. Their value is based on the type of amino acids they contain, which combine with nitrogen and form thousands of different proteins necessary to build and repair cellular tissue. This takes place during digestion when hydrochloric acid and enzymes break down the intact protein molecule into amino acids so they can be absorbed through the intestinal wall. Of 22 known amino acids, 13 can be produced by the body, synthesized by glands like the liver. These–alanine, arginine, asparagine, aspartic acid, cysteine, cystine, glucine, glutamic acid, glutamine, hydroxproline, proline, serine, and tyrosine– are called nonessential amino acids. They can safely be omitted when enough nitrogen and other nutrients are supplied.
Essential amino acids, used for building tissue and other functions just discussed, cannot be made by the body but must be taken directly from our daily intake of food. They are–histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Those who are vegetarians should be aware that one amino acid cannot replace another.
When food contains the essential amino acids it is considered a complete protein. With the exception of soybeans, all complete proteins are derived from animal sources: meat, fish, eggs, poultry, cheese, and milk. Although most gelatin comes from an animal source, it does not fall into this category because it lacks the necessary amino acids essential for building tissue and repairning the body. Certain plant foods, like rice, potatoes, nuts, breads, and grain cereals, contain the essential amino acids but in lesser quantities than animal foods. Many cereals and rice are low in lysine, while dry beans, peanuts, and brewer’s yeast are low in methionine. It would be necessary to eat a pound of potatoes to provide the necessary amino acids found in only an ounce of meat. Keep in mind that the amino acids found in animal proteins are absorbed efficiently, their rate ranging from 90 to 95 percent, while the digestibility of some plant proteins may be as low as 73 percent. Vegetarians also run the risk of miscombining vegetable proteins and thus failing to form complete proteins containing all the essential amino acids. The growth and reproduction of cells demand that all the essential amino acids be ingested at the same time in the same meal. A missing amino acid cannot be supplied several hours later and still find the essential ones waiting to be assembled into a complete protein before being digested. Eggs are a prime example of a complete protein, containing all of the essential amino acids in sufficient amounts to maintain life and support growth.
Columbu, Dr. Franco. The BodyBuilder’s Nutrition Book. Chicago, Illinois: Contemporary Books, 1985.
Schwarzenegger, Arnold. The New Encyclopeida of Modern BodyBuilding. New York: Simon & Schuster Paperbacks, 1985. Rev. ed. 1998. 1-800.
