Information About Proteins
Proteins are found in every cell body and perform a myriad of functions. Proteins are made up of sequences of amino acids. There are 22 amino acids which are categorized as essential or non-essential. Essential amino acids (EAA’s) must be acquired from the diet as the body cannot synthesize them, non-essential amino acids can be made within the body. Animal proteins are termed ‘complete proteins’ because they contain all EAA’s while most plant protein sources are deemed as ‘incomplete proteins’ because they are missing some EAA’s. To create a meatless meal containing all EAA’s, you must simply match two foods whose combined EAA’s create a complete amino acid profile, beans and rice for example. If the body does not obtain adequate amounts of EAA’s it will start to break down its own muscle to fuel other vital body function.
There are many sources of protein each having its own set of pro’s and con’s including price, fat content, digestibility, and amino acid profile. The importance of each of these points is weighted differently from person to person. Universally, the quality of different protein types are scored using the protein digestibility-corrected amino acid score (PDCAAS) where a score of 1.0 indicates the protein exceeds EAA needs of the body. This is the most widely accepted method for quantifying protein quality but even within a perfect score of 1.0 there is some variation quality, in part due to digestibility and amount of amino acids. Whey and bovine colostrum (BC) are the two highest quality protein sources however, BC can be quite expensive.
Milk is made up of about 80% casein and 20% whey and is a good source of protein and carbohydrates, providing about 8 g of protein per cup. Milk is a great example of a pre or post workout supplement. Whey is separated from whole milk as a byproduct during the cheese making process. Whey is quickly digested which allows for a rapid release of amino acids into the blood stream, is generally lower in fat than milk, and because the majority of allergens are in the casein portion of milk, whey is tolerated by most lactose intolerant people. Casein protein is also a high quality source but with a slower digestion rate. Faster digestion, frees amino acids more rapidly for protein synthesis. A casein rich meal can be beneficial during times of fasting, such as during sleep, as the amino acids are released slowly, over an extended period of time. All three of these dairy sourced proteins are rated 1.0 on the PDCAAS.
Egg protein is also a 1.0 on the PDCAAS, and is of equal quality as milk, but is somewhat more expensive if purchased as a powdered supplement. Eggs themselves serve as a relatively cheap and easy way to fuel the body with protein pre or post workout.
Soy serves as a great protein option for vegetarians as it has a PDCAAS of 1.0, but lacks the amino acid methionine and is therefore lower quality than the afore mentioned sources. Due to its plant source, soy is a lower fat option than many other protein sources. There is debate concerning the negative effects of soy in men causing some to avoid it for an alternate protein source.
Meats are the most commonly thought of protein source yet only rank from 0.8 to 0.9 on the PDCAAS. A couple of the draw backs to meat sources are the higher levels of fat and inferior digestibility. This is not to say that meat is not a good source of protein, it just should not be the only source of protein in an athlete’s diet.
The Recommended Daily Allowance (RDA) for protein is:
1.0g/kg body weight/day for children 11 to 14
0.8 to 0.9 g/kg body weight/day for adolescence 15 to 18
0.8 g/ kg body weight/ day and 0.8 g/ kg body weight/ day adults
0.8 to 1.0 g/kg body weight/day adults in general fitness programs
1.5 to 2.0 g/kg body weight/day for strength athletes