I would like to discuss the concept of ‘Biological Value’ this is something that is very simple, but very misunderstood or just receives little attention around the forum. As a first thought you may think it is the nutritional facts of a certain food, or how much it is worth in nutritional value. In part, you are most certainly right, but it is more closely associated with protein, protein quality specifically.
_____________________________ _____________________________ _____________________________ ____________Biological value is the amount, or percentage of protein that the body is able to absorb and use from a certain protein source. To simply put it; protein in certain foods is worth more than in others. A protein from a certain food will be absorbed better than a protein from a different food source, even if both are given in the same quantity, protein-wise.
Before I go further, I would like to explain what a ‘protein’ macronutrient is, in the language of science. Protein is a sequence of amino acids; a different sequence represents a different protein type, or function. Every amino acid is also constructed from a different sequence of atoms. These amino acids are all linked together by a series of peptide bonds when a protein is a whole molecule (before it is broken up, by enzymes for example) All protein kinds contain nitrogen, this nitrogen is very crucial for biological value as well as metabolism and other bodily functions such as the growth of; fingernails, hair, ligaments, and muscles.
Depending on the biological value of the foods you eat, the more nitrogen your body will also be able to retain, or excrete in the form of urea (urine) which also assists in the removal of many toxic materials from your body. Nitrogen accumulation also assists in the buildup of enzymes, or a special type of protein which help your body break down food by acting as a catalyst in the metabolic process (speeding it up), which in turn helps your metabolism. Now don’t think that you should eat nitrogen or something, every protein source you eat contains enough of it, it just varies how much of it will actually be utilized.
As you can tell, nitrogen and biological value are closely linked to one another and that is because nitrogen is used to measure the biological value of the food. Biological value is measured by the amount of nitrogen initially present in a protein source, and the amount of nitrogen that ends up being excreted. The amount that remains, percentage, is the amount that will be used to construct bodily tissues. However, this is not always the most accurate method to measure biological value and can range between individuals depending on gender, age, and physique. It is also important to note that athletes (body builders included) require a higher amount of protein due to the stress, and higher metabolic rate that the body undergoes due to training.
_____________________________ _____________________________ _____________________________ ____________All protein is ranked according to its biological value. When this system of ‘ranking’ protein was introduced, eggs were initially given the highest ranking of 100, because they are the most bio-available protein. Due to the high quality of egg protein all other protein sources were compared to it, and ranked upon a 0 to 100 scale (100 being highest, 0 lowest)
After a certain period of time, whey, isolated from milk, was discovered. Whey protein had a higher biological value than egg protein and due to this a new way to measure the biological value of protein was necessary. The new system was a percentage based system, which measured the amount of nitrogen remaining in the body after excretion, which is what I explained above.
Hopefully that somewhat explains what biological value is and how it is measured.
_____________________________ _____________________________ _____________________________ ____________I would also like to provide a biological value list of foods that are common in most diets. Here it is;
Whey – 100
Whole Egg – 100
Cow’s Milk – 91
Egg White – 88
Fish – 83
Beef – 80
Casein – 80
Chicken – 79
Soy – 74
Wheat Gluten – 64
Rice – 59
Wheat – 54
Beans – 49
As you can tell, whey protein, eggs, dairy and meat products have the highest biological value. These values are based upon a percentage system, meaning that these numbers represent the percentage of nitrogen absorbed.
The reason I wrote this thread is to try to explain that when measuring protein consumption, your body doesn’t absorb all of it. Meaning that if, let’s say a 150lbs bodybuilder eats 150g protein a day, maybe only 120g will be used and absorbed by the body. The other 30g will be excreted or used for other bodily functions. I know it can be very time demanding to measure the amount of protein that your body is most likely to absorb, using the biological value system, but it should be put under consideration at least when measuring protein consumption.
Something else that I think is important to note it that it is suggested that after waking up or after a workout, both catabolic states, it is best to consume a high biological valued protein. It is ideal due to the ability of protein to reach the muscles for optimum results. That is why many bodybuilders, including myself, would advise to have a protein shake. Of course you can eat a can of tuna, or a few glasses of milk as well, but the whey will reach your muscles faster than any other food source.
_____________________________ _____________________________ _____________________________ ____________Works CitedNeil A. Campbell, Jane B. Reece, Lisa A. Uray, Michael L. Cain, Steven A. Wasseman, Peter V. Minorsky, Robert B. Jackson “Biology, 8th Edition” : 77-86, 214-215, 325-350. Thur. 16 Sept. 2010.
Behar, Jeff. “Methods of Assessing Protein Quality” Bodybuilding.com. Fri. 17 Sept. 2010.
http://www.bodybuilding.com/fun/protein3.htm