Proteins Role in your Diet
Protein is the body’s primary building material. It is used to construct and maintain bones, muscles, cartilage, skin, blood cells, hair, and nails. Protein is also used to make many of the biochemical substances (enzymes, hormones, transport molecules, neurotransmitters, and vitamins) the body uses to perform essential metabolic functions. Protein is one of three nutrients that provide calories. The others are fat and carbohydrates. Each gram of protein provides 4 calories.
The word protein comes from the Greek word proteios meaning primary.
The main sources of protein in the typical American diet are meat, fish, poultry, eggs, milk, cheese, and yogurt. Plant-based foods such as legumes (dried beans, lentils, peas), seeds, nuts, and grains also provide small but valuable amounts of protein.
Protein is unique among the calorie-providing nutrients (protein, fat, and carbohydrate). All three nutrients contain carbon, hydrogen, and oxygen, but only protein contains the chemical element nitrogen. The four elements that make up protein are arranged into 20 structurally unique building blocks called amino acids. The body can make about half of the 20 amino acids. The others, called essential amino acids, must be obtained from the diet.
Animal Versus Plant Proteins
Animal proteins provide the best array of essential amino acids, supply other essential nutrients like B vitamins, iron and zinc, add a natural, salty flavor to meals, and because of the time it takes the body to digest them, help make a meal feel “satisfying.” Animal-derived proteins, however, can be high in fat, particularly saturated fat.
Plant proteins tend to contain less fat than animal proteins, but since they are digested more quickly and less completely, they don’t provide the same sensation of fullness. Individual plant proteins tend to lack one or more of the essential amino acids and must be eaten in appropriate combinations to provide adequate nutrition. For example, grains tend to be low in one amino acid, whereas legumes are low in a different one. Combining grains and legumes such as bean and rice, or peanut butter and bread provides a complete protein because, together, they contain all of the essential amino acids. It is possible to create a healthy vegetarian diet, but it takes special planning to ensure good nutrition.
How Much Protein Should People Eat?
Protein needs are determined in large part by a person’s lean body tissue (muscle, organs, bone, and skin), which can be estimated by knowing their healthy weight range for their height. Most adults need 0.8 grams of protein for each kilogram (2.2 pounds) of healthy body weight for their height. For instance, a 120 pound, 5′ 5″ woman needs about 44 grams of protein a day (roughly the amount of protein in 2 servings of meat). If the same woman gained 30 pounds, she would still need about 44 grams of protein per day because fat tissue does not contain or require additional protein.
Obese individuals will need slightly more protein because their bodies use protein to make extra muscle and skin to accommodate their extra weight. Elite athletes, people recovering from a traumatic injury, and pregnant or nursing women also need a bit more protein each day, as do growing children and teens.
From a health standpoint, it is reassuring to know that most Americans get too much protein, not too little. The table below illustrates the amount of protein a person would consume each day if he or she were to follow the guidelines suggested by the Food Guide Pyramid.
|Food Group||Grams Protein/ Serving||Number of Servings||Total Grams Protein|
|Milk||8 -9 grams per cup||2-3||16-24|
|Eggs||5-6 grams each||1||6|
|Legumes||6 grams per half cup||1||6|
|Meat||21 grams in 3 oz||2||42|
|Grains, Cereals,Breads||2 grams per ½ cup or slice||6-11||12-22|
|Fruits & Vegetables||0-2 grams per ½ cup||5-9||0-18|
Protein in Weight Loss and Management
The human body needs to maintain its blood glucose (sugar) level in a narrow range for the brain, nervous system, red blood cells, and eyes to function properly. Body fat can be broken down for energy, but it is not a good source of glucose. Protein is a good source. Strict dieting can cause the human body to burn its own muscle tissue to produce calories and glucose (blood sugar). While losing lean muscle is not the dieters’ goal, it is a fairly common result when people follow fad diets. Furthermore, without adequate protein or fat in their meals, dieters may be overcome by hunger and eat more calories than they intend, thus thwarting their success.
Before beginning any weight loss program, people should make sure it contains enough protein to meet their bodies’ protein requirement.
Owing to its ability to create a sense of fullness, consuming lean protein such as skinless chicken or turkey breast, fish, or reduced-fat dairy products at each meal and snack can help people lose weight and keep it off.
When cutting back on calories, it is important to follow established healthy weight loss guidelines to help control hunger, ensure the weight you are taking off is primarily fat, and meet your other nutritional needs.