What is Protein

By Christopher Algieri

Protein, one of the three fundamental and essential macronutrients, is the most abundant nutrient found in the body (other than water). Protein is the body’s major building block and makes up the brain, muscles, blood, skin, hair, nails and connective tissues. It also makes up the antibodies of the immune system, many hormones, and all of the enzymes that regulate the body’s biochemical activities.

Dietary protein should only make up 10-12 percent of daily calories. The lion share of the total calories that are required by the human body should come from carbohydrates (50-60%) and fat (25-35%).  The average American diet provides more than enough calories from protein and protein-deficiency is an extremely rare condition in most industrial nations. Protein, especially from animal sources, is often high in calories and fat and can lead to overweight and obesogenic conditions. Another reason that protein should makeup a relatively small portion of total caloric intake is because its chemical complexity requires the body to work extra hard during breakdown and absorption of the nutrient. This extra work can tax many of the body’s organ systems.

What is Protein made of?

Protein is an organic substance composed of carbon, hydrogen, oxygen and nitrogen. Each protein molecule is made up of varying combinations of amino acids. There are 20 different amino acids that are coordinated in a countless number of ways to produce the various kinds of proteins. Of the 20 amino acids, 9 are essential. Essential means that they cannot be produced in the body and need to be obtained through diet.

What does Protein do?

Protein supplies the amino acids that the body needs to carry out daily activities. These include tissue growth and maintenance, healing of wounds; height and weight increase in children, and production of human milk in lactating females. Degradation and reconstruction of body tissue is a constant process called protein turnover that is essential for health. Enzymes, which are made of proteins, are essential for releasing the energy found in foods during digestion and for rebuilding new substances from materials obtained in the diet.

Protein can also be used as an energy source. Proteins are stripped of their nitrogen in the liver (called deamination) and burned for energy. This occurs when the diet does not contain enough carbohydrate or fat. Protein is not the preferred source of energy because of the metabolic cost your body incurs during breakdown and metabolism of the large and complex protein molecule. Excess protein is broken down and stored as glycogen or fat for future use. Protein provides 4 kilocalories per gram.

Protein Quality and Complimentary

Every food, besides pure fat (oil), contains some protein, and every food differs in its amino acid makeup. Some foods provide a better makeup of amino acids and the foods that contain all 9 essential amino acids are considered high quality or “complete” proteins. All animal proteins are complete while all vegetable sources (other than soy) are deficient in one of more of the essential amino acids. Since all plant foods are not low in the same amino acids, they can be combined to create complete proteins. Two incomplete proteins that compensate for each other’s shortcomings to produce high quality protein are considered complimentary proteins.

Complimentary Protein Pairings

Legumes and grains (rice and beans)

Grains and Dairy (cereal and milk or macaroni and cheese)

Legumes and Seeds (Asian noodles with sesame dressing)

Grains and seeds (peanut butter sandwich)

Virtually every society has paired vegetables sources of proteins to produce complete proteins in their respected cuisines. Some examples of common complimentary proteins by ethnic cuisine:

Black beans and Tortillas (Mexican)

Dahl (split peas) and rice (Indian)

Chickpeas and Bulgur Wheat (Middle East)

Tofu and vegetables (Asian)

Black-eyed Peas and rice (American)

Baked Beans and Corn Bread (American)

This is how vegetarians are still able to have a well-balanced diet that provides ample amounts of protein for growth, synthesis and maintenance. 

Protein Requirements

Protein needs are based upon a number of factors including age, body size, composition of diet, state of health, and activity level. The RDA (Recommended Dietary Allowance) for protein in a healthy adult is 0.8 grams per kilograms of ideal body weight.  This is higher for certain populations such as pregnant women and extremely active athletes, but should not exceed 1.5 grams per kilogram. Over consumption of protein has been indicated in a number of hazardous conditions in healthy individuals but never clinically proven. High-protein diets have been correlated with liver and kidney disease, as well as the osteoporosis. Diets that are high in protein tend to be high in fat, (especially saturated fat) and cholesterol, which in excess can contribute to the development of arthrosclerosis and obesity.

Sources of Protein

Meat- beef, poultry, fish, pork, eggs

Dairy-milk, cheese, yogurt

Legumes- chickpeas, black beans, lentils

Whole-grains-brown rice, quinoa, oats, bulgur wheat

Nuts and Seeds- almonds, walnuts, sunflower seeds, peanuts

Soy-tofu, soybeans, miso