Carbohydrates, fat, protein and water are considered essential macronutrients. According to the USDA, carbohydrates should comprise about half of all dietary calories, fat should come in around 30 percent, leaving daily protein intake about 20 percent. Even though recommended protein intake is the lowest of the major energy nutrients, it is important for a number of essential body functions.
Protein's Role in the Body
Protein is essential for building, repairing and maintaining lean tissue, including muscles, bones and cartilage. Protein also supports blood clotting mechanisms, hormone production and fluid balance. Protein provides structure for all cells within the body.
Protein Sources
Protein comes from meat as well as from nuts and other non-meat sources. Meat protein includes beef, poultry, fish and seafood, as well as eggs and dairy products. Meat is considered a complete protein, meaning all essential amino acids are present. But many of these sources can also be high in saturated fat, which is damaging to the cardiovascular system. Non-meat sources include nuts and seeds, grains, soy and other legumes. Most vegetable sources are not complete proteins, with the exception of soy. Vegetables offer both protein and fiber. Many nuts and seeds also supply valuable monounsaturated fat, which helps protect the heart. If you choose to reduce or exclude meat from your diet, it is important to eat from a variety of protein sources to ensure you get all essential amino acids.
How Much Protein is Necessary?
According to the USDA, 5 1/2 oz. of meat, or its equivalent, is all you need each day on a 2000-calorie diet. Equivalent portions include one egg, 1/2 oz.f nuts, 1 tbsp. of peanut butter or 1/4 cup of tofu or cooked legumes. You can form your own food plans, based on sex, age, body size and physical activity level on the USDA's MyPyramid.gov website.
Athletes' Requirements
Both endurance and strength athletes have higher protein requirements, only because they have higher caloric needs. The 50:30:20 ratios for macronutrients still apply. Protein intake can also be based on body weight. Specific recommendations published by Peter Lemon, Ph.D. in the "Journal of the American College of Nutrition," are based on body weight. Endurance athletes require 1.2 to 1.4g of protein per 1kg of body weight; strength athletes require slightly more at 1.6 to 1.8g. Based on Lemon's research, a 200 lb. endurance athlete requires 432 to 504 protein calories per day.
Based on this calculation, it is possible to consume enough dietary protein without using supplements. Muscle tissue grows at a controlled rate and you cannot make it grow faster by eating more protein. A basic underlying physiological principle is the need for energy. If daily caloric needs are not met, especially during periods of high intensity training, muscle tissue will be catabolized, or broken down, regardless of how much protein you eat. Carbs are integral fuel sources immediately after exercise to replenish muscle energy stores. Protein intake is important within the next few hours but at about a 3:1 ratio of carbs to protein.
Health Problems Associated With Too Much Protein
According to Dean Ornish, famed cardiologist, in an interview with the Huffington Post, a diet high in protein places a tremendous burden on the liver and kidneys. Protein metabolism produces ketones; ketones in excess can be toxic and harmful to the body. Dehydration also becomes a concern as the kidneys try to flush away the toxins. Excess protein can also cause excretion of calcium, which may contribute to osteoporosis. Consuming too much animal protein, especially from red meat, has been linked to heart disease and several types of cancer including colon, breast and prostate. Moderation is key to healthy eating.
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