If there’s one macronutrient that fitness-minded folks focus on more than any other – it’s protein. It’s like we just can’t get enough. But how much do your really know about protein? You can probably list 10 good protein sources off the top of your head, but let’s dive a little deeper.
WHY do we need protein?
Is essential for the growth and recovery of muscles, making it a priority when you’re focusing on gaining muscle. It also preserves lean body mass and spares muscle breakdown during exercise, making it ideal for when you’re focusing on cutting body fat. Also, proteins make up about 75% of the dry weight of most of the cells in your body, so it makes perfect sense that we as athletes are so focused on it.
So WHAT exactly is protein?
Proteins are large molecules called polypeptides, which are made of basic building blocks called amino acids (remember that from high school biology?) There are 22 amino acids that are biologically important to the human body, and 9 essential amino acids that the human body CANNOT produce by itself. The essential amino acids are histidine, isoleucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine.
It’s important to know about the essential amino acids because there are 2 categories of protein – complete and incomplete. Incomplete proteins, like plant proteins, lack at least one of the 9 essential amino acids. Complete proteins contain all 9 in amounts sufficient for muscle maintenance and a “normal” growth rate. Completely proteins include eggs, milk, milk products and most animal proteins.
HOW much protein should you take in?
This is where things get personal. You’re going to hear some people say 1 gram for every pound of body weight, while other people say to double that. Still others will say to take in no more than 40g per meal. In short… there is no ONE right answer. It depends on a myriad of things, from your body composition to your activity level to your genetically inherited tolerance level to your ability to digest protein. If you’re not taking in enough protein, you’re putting yourself at risk for sacrificing muscle mass. Too much, and the protein is converted to fat, increases toxic blood ammonia and uric acid, and leaves you pretty darn constipated. The Recommended Daily Allowance (RDA) for someone of average weight and activity level is 0.8 grams per kg of body weight. For athletes, however, 1.5-1.8 grams per kg of body weight is recommended – DOUBLE the RDA for average folks. As for bodybuilders, most typically double it again! So, to summarize: 0.8g/kg of body weight for the average person, less if you are overweight, 1.5-1.8g/kg for athletes.
The important thing to remember is that NOT ALL PROTEINS ARE CREATED EQUAL!!! Proteins receive a Biological Value rating based on the proportion of protein from a food source that can be digested and used in protein synthesis in our cells. This all depends on the ratio of nitrogen absorbed by the body from protein, and the nitrogen excreted. The higher the BV rating, the more usable the protein source is for your body. Since this is essentially a percentage, going over 100% doesn’t really make sense. You can’t absorb 137% of the protein from one source, however due to the way the BV level is calculated, it is possible to have a BV rating over 100. So, if you ingest 24g of protein from a source that has a BV rating of 100, your body will use all 24g of protein. If you ingest 24g of protein from a source with a rating of 75, your body will only be able to use 18g of that protein. Below is a chart showing several common sources of protein for your reference. Choose wisely!
U.S Dairy Export Council, Reference Manual for U.S. Whey Products 2nd Edition, 1999 and Sarwar, 1997.
Which protein is best? J Sports Sci Med. 2004 Sep; 3(3): 118–130
Effects of exaggerated amino acid and protein supply in man. Fern EB, Bielinski RN, Schutz Y; Experientia. 1991 Feb 15; 47(2):168-72