Protein and Amino Acids: How Your Body Breaks Down and Uses Protein

Published on 10/24/2013 by

This is a guest post by Mitchell Vanderkodde

Female endurance runner in hillsMany endurance athletes shy away from protein in an effort to avoid "bulking up". The human body needs protein to not only repair damaged muscle, but to function normally. By adding the right amount to your recovery regimen, you will help keep your muscles healthy and primed for their next workout.


Unfortunately, the protein that we eat is in a different sequence than the body needs, so it must be broken down into its smallest form (known as amino acids) before the body can then build it back up in the sequence that it needs.Our DNA determines this sequence.

Amino Acids

Amino acids are molecules that contain, at a minimum, a Carboxyl Group (COOH) and an Amino Group (NH2). They are created (synthesized) in plants, animals and even humans.

Complete Protein

Amino acids that humans cannot synthesize are called Essential, and those that humans can synthesize are called Non-Essential. A food that contains every essential amino acid is called a complete protein, such as whey or animal protein. It is also possible to combine incomplete proteins, like beans and nuts, to create a complete protein.


Protein digestion takes place in the stomach and small intestines, with assistance from the pancreas. The stomach secretes an enzyme which accounts for 20% of protein digestion, while pancreatic enzymes are responsible for the majority of protein digestion. By the time the protein makes it to the small intestine, it is in the form of polypeptides (short chains of amino acids) and individual amino acids. The small intestines finish the digestion process, breaking the polypeptides into di- and tri-peptides (chains of 2 and 3 amino acids), which the intestinal cells are able to absorb.

Amino Acids in the Body

The body uses amino acids for energy and to repair damaged tissue. Any excess are converted into keto acids and urea. Keto acids can be converted by the body into glucose to be used for energy or stored as fat. Urea is secreted in sweat and urine.

Muscle Repair

When muscles expand and contract during strenuous exercise, they become damaged. The body uses amino acids in the blood stream to repair these muscles. Protein also aids in muscle repair by building enzymes in the body. Over time, these enzymes allow muscles to adapt to endurance sports, lessening soreness and decreasing recovery time.

When to Take Protein

The body can only process up to 30 grams of protein at a time. Because of this, timing protein intake is just as important as total protein intake. After a workout, your body is primed for protein ingestion. 10-20 grams of protein both immediately before and after a workout is enough to satisfy your body's recovery needs. Whey protein has even been shown to be present in the blood stream in as little as 15 minutes after ingestion.

Recommended Protein Intake

The body is only able to process up to.91 grams of protein per day, per pound of body weight. So a 180 pound individual can process no more than 160 grams of protein in a single day. For most athletes, the following table represents the recommended protein intake, per pound, per day (the number in parenthesis represents total grams for a 180 pound individual).

Sedentary: 0.36 g/lb (65 g per day)

3-5 workouts per week: 0.45 g/lb (81 g per day)

5+ workouts per week: 0.55 g/lb (99 g per day)

Endurance training with enough recovery protein at the right time will keep your muscles healthy and primed for their next workout.

About The Author:
Mitchell is a US Marine Helicopter pilot and co-founder of �bloc Nutrition, maker of �bloc Endurance Recovery Drink Mix. You can follow him on Twitter @mitchvk, or check out his website,

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