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The Effect of Dietary Protein on Your Muscles

It’s fairly common knowledge these days that protein is “good” for one’s muscles. However, most folks don’t really understand what it is that dietary protein actually does to support muscle fiber in the body.

Breakdown and Repair
To begin with, let’s get clear about what muscles we’re talking about here. There are three distinct types of muscle fiber in the human body. The digestive tract and other internal organs are primarily smooth muscle. The heart is cardiac muscle. The muscles that help move bones and power the body’s outward movement are skeletal muscle. Skeletal muscle is what most people refer to when they talk about dietary protein’s effect on muscle growth. Smooth and cardiac muscle is constituted through a different cellular process.

Skeletal muscle is almost entirely protein. Think about it. Animal protein (you know, meat) is simply various cuts of animal skeletal muscle. The synthesis of muscle protein is essential to the body’s ongoing growth, repair, and maintenance of the skeletal muscle groups. Skeletal muscle is constantly broken down through the many physical activities that the body endures. All things being equal, the longer and/or higher the intensity of the activity, the more skeletal muscle breakdown there will be. This breakdown process is known as catabolism. The body’s process of repairing the damage done and building muscle is known as anabolism. This is where dietary protein becomes essential.

The anabolic process starts when dietary proteins are consumed. During the digestive process, the body secretes various enzymes throughout the digestive tract and these break those proteins down into their individual amino acids. When these reach the small intestine, the amino acids are absorbed and then circulated throughout the body. The skeletal muscles use these amino acids as building blocks to create the proteins of new muscle tissue. So in essence, dietary protein fuels the anabolic process.

How to Get the Most out of Dietary Protein

Eat the Right Amount
The RDA for dietary protein is 0.8 g per kilogram of weight in sedentary adults. This equates to about 56 grams per day for an average male and 46 grams per day for an average female. Keep in mind, however, that this is the amount necessary to support repair of the catabolic effects from a sedentary lifestyle. Once activity, exercise and/or hard training is added into the mix, the body’s protein needs go up. Dr. Peter Lemon from the University of Western Ontario found that the RDA for those engaged in strength training is about double that of a sedentary individual, which is roughly 1.7 – 1.8 grams of protein per kilogram of body mass per day.

The other important consideration is how much protein to consume per meal. Most researchers agree that 20 grams of protein is the most effective amount to consume per serving. The body can only assimilate so much dietary protein at once. Beyond that, excess dietary protein can be converted to fat and stored that way—but it can’t revert back to protein again. The liver converts excess amino acids to other usable molecules but the process creates ammonia, which is transformed into urea by the liver. The body flushes urea from the system through urination, which is why consuming excess protein can have a dehydrating effect. Of course, if you ingest too little dietary protein, the anabolic process will suffer.

Choose the Right Protein
There are 21 amino acids the body uses for anabolism and every type of dietary protein is comprised of various amounts of these. The body requires a certain amount of each and while it can create some of these on its own, others have to be ingested. These are known as the essential amino acids and a complete protein contains all of nine essential amino acids. Studies have shown that the most effective anabolic process is possible only if high quality complete proteins are ingested on a regular basis. Complete proteins include: all animal proteins, including eggs and dairy, and certain whole grains such as quinoa.

Timing and Consistency
As all proteins are comprised of different combinations of amino acids, they are digested at different rates. One study found that most bodies can digest 8-10 grams of whey protein per hour, but can only absorb about half as much casein per hour. Because whey is absorbed so quickly it is a great option for post-workout recovery (when the muscles can accept the most protein for anabolic repair). However, during other times of the day, a protein with a slower absorption rate is a better option. For example, one study found that casein was the superior protein to consume before sleeping to promote maximum overnight recovery.

So yes, protein is quite good for your muscles. In fact, it’s essential. However for maximum effectiveness and fueling the anabolic process, you should consume high-quality dietary protein regularly and in proper amounts.