High protein diets are diets in which 20% or more of the total daily calories comes from proteins. A very high protein diet is one where 30% or more of the total daily calories comes from protein. By comparison, in the average American diet about 12–16% of calories come from protein.
High protein diets have been popular off and on since the 1960s. In the 1960s, Dr. Maxwell Stillman of the Stillman Diet was one of the first to advocate a high protein, no carbohydrate, low fat diet for fast weight loss. In the 1990s, diet books promoting high protein diets began to appear on bestseller lists. The most popular of these “new” high protein diets was the Atkins Diet. Other high protein diets include the Zone Diet , Protein Power, and Sugar Busters. These diets are the heirs to the Stillman Diet, slightly modified to include some carbohydrates , and repackaged with some updated terminology and scientific explanations. They encourage high protein diets for weight loss and/or for bodybuilding.
All human protein is made from about 20 different small molecules called amino acids. Out of these 20 amino acids, nine are considered essential amino acids. They are essential because the body cannot make them from other nutrients and they must be obtained fully formed from diet.
Both animals and plants are sources of protein. Animal protein has the higher biological value because it is a complete protein. Complete proteins contain all nine essential amino acids. Animal proteins include meat, poultry, fish, egg whites, and dairy products.
Plant proteins have a lower biological value because they are incomplete proteins that do not contain all nine essential amino acids. Some plants are better sources of protein than others because they lack only one or two essential amino acid. Better plant proteins include dried beans and bean products such as tofu (made from soybeans), nuts, and grains such as corn and quinoa. Many cultures have developed dishes such as red beans and rice or corn tortillas and beans that combine these incomplete proteins in the same meal to provide all the essential amino acids needed for health.
Amino acid —molecules that are the basic building blocks of proteins.
B-complex vitamins —a group of water-soluble vitamins that often work together in the body. These include thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxine (B6), biotin (B7 or vitamin H), folate/folic acid (B9), and coba-lamin (B12).
Dietary fiber —also known as roughage or bulk. Insoluble fiber moves through the digestive system almost undigested and gives bulk to stools. Soluble fiber dissolves in water and helps keep stools soft.
Enzyme —a protein that change the rate of a chemical reaction within the body without themselves being used up in the reaction.
Essential amino acid —an amino acid that is necessary for health but that cannot be made by the body and must be acquired through diet.
Glucose —a simple sugar that results from the breakdown of carbohydrates, and under some conditions proteins and fats. Glucose circulates in the blood and is the main source of energy for the body.
Glycogen —A compound made when the level of glucose (sugar) in the blood is too high. Glycogen is stored in the liver and muscles for release when blood glucose levels are too low.
Mineral —an inorganic substance found in the earth that is necessary in small quantities for the body to maintain a health. Examples: zinc, copper, iron.
Osteoporosis —a condition found in older individuals in which bones decrease in density and become fragile and more likely to break. It can be caused by lack of vitamin D and/or calcium in the diet.
Quinoa —a high-protein grain native to South America (pronounced keen-wah).
Vitamin —a nutrient that the body needs in small amounts to remain healthy but that the body cannot manufacture for itself and must acquire through diet.
The federal Dietary Guidelines for Americans 2005 recommends that no more than 15% of an individual’s daily calories come from protein. The American Heart Association and the National Institutes of Health state that protein equaling 10-12% of an adult’s total daily calories or about .36 g/lb (.8 g/kg) of ideal body weight is a reasonable amount of protein to maintain health. By contrast, some of the high protein diets recommend between 35% (Atkins) and 64% (Stillman) of daily calories come from protein. This is equivalent to about 1–2 g/lb (2.2-4.4 g/kg) of ideal body weight.
Extra amino acids are not stored in the body. Instead, they are split apart by enzymes, and the part containing nitrogen is excreted by the kidney in urine, while the remainder is either converted into glucose (a simple sugar) and used for energy or stored as glyco-gen, a compound that can later be reconverted into glucose.
High protein diets are also high in saturated fats . Saturated fats are animal fats. They are considered “bad” fats because they raise the level of LDL cholesterol (“bad” cholesterol) in the blood. High LDL cholesterol levels are associated with an increased the risk of heart disease. High protein diets also restrict calories by severely restricting carbohydrates. Whole-grain carbohydrates are a significant source of B-com-plex vitamins . There are groups who need extra protein—rapidly growing adolescents, pregnant and nursing women, bodybuilders, endurance athletes, and some cancer patients— but these groups need to increase protein as part of a well-balanced diet.
High protein diets do promote fast initial weight loss, although most of the loss comes from losing water . The reason for this is that they drive the body into a state called ketosis. The body prefers to break down carbohydrates into glucose and use that glucose for energy. When the body is starved for carbohydrates, it begins converting fat into glucose. The process of converting fat into glucose releases water molecules which then leave the body as urine.
Dieters, of course, want to burn fat, but when they burn fat exclusively, a side effect of this reaction is that molecules called ketones build up in the blood. If the body is deprived of carbohydrates for a long time, these ketones accumulate and cause metabolic imbalances that can seriously harm the kidney and other organs. Ketones are part of the body’s defense against starvation. They suppress appetite. They also cause bad breath.
High-protein diets offer fast weight loss. The Stillman Diet claims an individual can lose up to 30 lb (13.5 kg) in 28 days. Some high protein diets also claim
QUESTIONS TO ASK THE DOCTOR
- Is a high protein diet better for me than a regular calorie-reduced diet?
- Does this diet pose any special risks for me that I should be aware of?
- Do I have any special dietary needs that this diet might not meet?
- Do I need to take a dietary supplement while I am on this diet?
- What are my risk factors for cardiovascular disease and how will this diet affect them?
- How long can I stay on this diet?
- Do you have any experience with the long-term success of this diet?
- If one of your family members wanted to go on a diet, would you recommend this one>
health benefits. The Zone diet claims it will improve physical and mental performance, prevent chronic cardiovascular diseases, improve immune system functioning, decrease signs of aging, and increase longevity.
Rapid weight loss does occur with high protein diets, but much of the loss comes from losing water. This weight soon returns when the dieter goes off the diet. Other health claims have not been proven by any rigorous, scholarly research studies.
The risk of kidney damage is greater in individuals with poor kidney function who choose a high protein diet. High protein diets put an extra workload on the kidney because the nitrogen-containing part of excess amino acids is split off and has to be removed from the body in urine. Although this is not usually a problem for healthy kidneys, it can cause more damage in kidneys whose functioning is already reduced.
Nothing about high protein diets is balanced. Virtually all high protein diets recommend that the dieter take some sort of vitamin or mineral supplement. By restricting carbohydrates, these diets reduce the amount of vitamins, mineral, and dietary fiber . High protein diets also increase the amount of calcium excreted by the kidney. This increases the loss of calcium from bone and can lead to osteoporosis . It also increases the risk of kidney stones, which are more likely to form when large amounts of calcium are present. Cholesterol levels increase on high protein diets because of increased intake of saturated fats associated with animal protein. Finally, when the body is in a state of ketosis, the ketones that accumulate make the body more acidic, and this can cause major damage to various organs.
High protein diets have come in for a lot of criticism, even though several studies have shown that the Atkins diet is not as problematic as was originally thought. Nutritionists find high protein diets, especially high protein, high fat, severely carbohydrate restricted diets, to be unhealthy, unbalanced, and generally unnecessary because of the well-documented risks outlined above. The public, however, has embraced high-protein diets such as the Zone Diet and the Atkins Diet, at least until the next new diet comes along. Bodybuilders, weightlifters, and others wishing to gain muscle mass also look favorably on high protein diets. The Mayo Clinic concludes that high protein diets are probably not harmful to healthy individuals with good kidney function. The American Heart Association condemns these diets because they appear to increase the risk of cardiovascular disease. No studies have been done on the long-term effects of high-protein diets.
Eades, Michael R. and Mary Dan Eades. The Protein Power Lifeplan. New York: Warner Books, 2000.
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American Dietetic Association. 120 South Riverside Plaza, Suite 2000, Chicago, Illinois 60606-6995. Telephone: (800) 877-1600. Website: <http://www.eatright.org>.
American Heart Association. 7272 Greenville Avenue, Dallas, TX 75231. Telephone: (800) 242-8721. Website: <http://www.americanheart.org>.
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Mayo Clinic Staff. “High-protein Diets: Safe if You Have Kidney of Liver Disease?” MayoClinic.com, June 8, 2006. <http://www.mayoclinic.com/health/high-protein-diets/AN00847>.
Northwesternutrition “Nutrition Fact Sheet: Protein.”Northwestern University, September 21, 2006. <http://www.feinberg.northwestern.edu/nutrition/factsheets/protein.html>.
United States Department of Health and Human Services and the United States Department of Agriculture. “Dietary Guidelines for Americans 2005.” January 12, 2005. <http://www.healthierus.gov/dietaryguidelines>.
WebMD. “Weight Loss: High Protein, Low Carbohydrate Diets.” October 1, 2005. <http://women.webmd.com/guide/high-protein-low-carbohydrate-diets>.
Tish Davidson, A.M.