Being the major component of all cells, including muscle and bone, protein is essential for life. It is needed for growth, physical development, cell creation and repair, and by the immune system to produce antibodies. Consuming too little protein (or too much) can lead to health problems.
Dietary protein is found in most foods and is the primary source of amino acids for the body. Foods containing protein include but are not limited to nuts, grain, beans, beef, chicken, fish, pork, dairy and eggs. Protein can also be found in vegetables and fruit.
Making Good Choices: Variety is Key!
Not all protein-containing foods are alike: each protein source has a different combination of amino acids. Some foods may contain high amounts of essential amino acids while other foods may be low. Foods that have greater amounts of essential and non-essential amino acids are considered "high quality" protein sources; those with lesser amounts of essential and non-essential amino acids are considered "low quality".
Examples of high-quality proteins include eggs, beef, fish, and milk. Low-quality protein sources include beans, potatoes and whole wheat bread. Although plant sources of protein are in general not as rich in the amount or variety of amino acids as animal sources, sensible vegan and vegetarian diets will provide more than enough. No food has all the elements you need, so by eating both high- and low-quality sources of protein, you make up for the shortage of amino acids in the one food with an abundance of amino acids in the other.
At one time, nutritionists enthusiastically recommended that people eat "complementary" foods at each meal. That is, they suggested eating a high-quality protein, such as tuna, together with a low-quality protein, such as whole wheat bread, at each meal. (Vegetarian examples would have been baked beans on toast or lentils and rice.) We now know that such assiduous food combining is not necessary. As long as the body gets both high- and low-quality proteins in a day, it can combine and use the amino acids themselves.
All foods have other nutrients in addition to protein, of course. Some also have qualities that are potentially harmful. Soy, for example, has ample protein, can provide fiber, and contains isoflavones, which help to protect against certain types of cancer and heart disease. Other beneficial sources of protein include: fish (essential fatty acids), eggs (essential fatty acids), beans (fiber), whole grains (fiber, vitamins, minerals).
Conventional corn fed beef, on the other hand, is a protein source containing high amounts of saturated fat, which can contribute to the development of elevated cholesterol and, over time, coronary artery disease. Whole milk, too, contains saturated fats. Bacon and salami contain protein, but their processing saddles them with carcinogens. Obviously, it doesn't pay simply to look at the raw numbers and choose the food with the most protein. Other considerations must go into the mix.
The recommended daily allowance (RDA) for healthy adults suggests that adults consume at least 0.36gm of protein for each pound of body weight (or 0.80gm per kilogram). This means an adult weighing 154 pounds should consume 56gm of protein each day (0.36gm per pound multiplied by 154 pounds equals 56gm of protein). It is important to emphasize that children, athletes, pregnant women and people with chronic diseases require different amounts of dietary protein.
While an increased-protein diet may benefit certain conditions, the foods consumed for a high protein diet are in the main meat, egg, and dairy products, which are high in cholesterol, fat, and animal protein, deficient in dietary fiber and carbohydrate, and can easily provide a serious imbalance of certain vitamins and minerals. Caution is advised.
Those with liver or kidney problems need to be particularly careful: Protein is metabolized by the liver and excreted by the kidneys into the urine. A high protein load can increase damage to these organs. Note that low protein diets (4% to 8%) are used routinely to treat patients with liver and kidney failure.
The timing of protein intake can markedly increase the effectiveness of l-dopa and thereby lead to reduced dosage requirements. Researchers now recommend that protein intake be kept as low as possible and that protein be included primarily in the evening meal.
Don't skimp on protein and fat to "make room" for large amounts of carbohydrates. Protein and fat give the body extended energy, help balance blood sugar and keep cravings at bay.
Adequate protein intake can prevent preeclampsia, and a higher protein diet can often successfully reverse preeclampsia.
A high protein, decreased fat diet and vitamin supplements may be recommended.
Virtually every study in which the carbohydrate intake was low enough to convert the body's primary fuel from glucose to stored fat has shown a drop in total cholesterol and improvements in risk ratios of total cholesterol to HDL, with a dramatic decrease in triglycerides.
An excellent book to read on the benefits gained from an adequate (not high) protein diet is "Protein Power: The High-Protein/Low Carbohydrate Way to Lose Weight, Feel Fit, and Boost Your Health-in Just Weeks!" by Michael and Mary Eades.
Protein supplements at 1 to 3 servings per day will help ensure sufficient amino acids and help prevent wasting.
Protein causes toxins to form in the digestive tract, so eating less protein will help decrease the buildup of toxins in the blood and brain.
Researchers from England state that chronic obstructive pulmonary disease may only worsen by eating a diet that contains an overabundance of high-carbohydrate foods. The results suggest that even small changes in the constitution of meals, especially in terms of less carbohydrate, may have significant effects on exercise tolerance and breathlessness amongst patients with COPD. [Diets Rich in Carbohydrates Worsens COPD, Medical Tribune, July 23, 1992; p.17]