Protein is one of the essential macronutrients in the diet. In the body it is found in skin, bones, muscle, blood and organ tissue. It is also a critical component of hormones and enzymes. A certain amount of protein is needed every day to build muscles and replenish the supply that was used.
Recommended Daily Intake
According to the Mayo Clinic, 10 to 35 percent of your total daily calories should come from protein. Based on a 2,000-calorie diet, this equates to about 50 to 175 g of protein a day. Legumes, poultry, seafood, eggs, meat, dairy products, nuts and seeds are all good sources of protein in the human diet.
Amino Acids
It is not surprising that there are different types of proteins. The building blocks of proteins are molecules known as amino acids. There are 20 different amino acids, but about half of these cannot be manufactured by the body and must be obtained through the diet. These are called essential amino acids. Besides consuming a specific quantity of proteins, you should also be sure that you are eating all of the essential amino acids.
Complete Proteins
Foods that contain all of the essential amino acids are known as complete proteins. These include most of the protein-rich foods such as meat, seafood, eggs and dairy products. Soybeans are the only plant products that would qualify as complete proteins. Otherwise, you can mix and match plant foods to arrive at all of the essential amino acids. Therefore, it is a good idea to find out how many of each amino acid you are consuming and, most importantly, whether a given food contains all of them.
Considerations
The recommended daily allowance for protein consumption is .8 g per kg of body weight, but this is only enough to replace the amount of protein lost through excretion. It is not quite enough to build a substantial amount of muscle. According to experts at Columbia University, the top protein intake should be 1.5 to 2 g per kg of body weight if you are engaging in strength training or exercise. This is toward the high end of the Mayo Clinic recommendations, but combined with an increase in total calorie consumption, protein intake should still only constitute about 15 to 20 percent of total diet. Additional protein intake is even useful as you age and begin to lose muscles.
Potential Downsides
Protein is mostly a structural and functional nutrient, so there is a barrier beyond which it may cease to be efficacious. However, there are very few downsides to high protein intake as long as it is used and not stored as fat. Some experts worry that it places stress on the kidneys, which helps excrete the nitrogen found in amino acids, but very few long-term studies have been done, especially on otherwise healthy individuals. Katherine Zeratsky of the Mayo Clinic recommends only following a high protein diet for three or four months at a time.
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