Physician Advisory

Health Risks of High-Protein Diets

• Colorectal cancer, cardiovascular risk, renal disease, osteoporosis, and particular risks to individuals with diabetes
• Deceptive statements commonly cited in press
• New patient registry established
• Possible legal liability

Recent media reports have publicized the short-term weight loss that sometimes occurs with the use of very-high-protein weight-loss diets. Some of these reports have distorted medical facts and have ignored the potential risks of such diets. Based on past experience with the fen-phen drug combination and other weight-loss regimens, you may expect that some patients will disregard even serious long-term health risks in hopes of short-term weight loss.

This advisory is intended to notify you of (1) risks from the long-term use of high-protein diets, (2) currently circulating misunderstandings and deceptive statements made in support of such diets, (3) the establishment of a registry for patients who have followed such diets, and (4) possible legal liability.

Health Risks

Despite press accounts of seemingly dramatic weight loss, the effect of high-protein diets on body weight is similar to that of other weight-reduction diets. Two recent studies (one at Duke University¹ and a second at the University of Pennsylvania, whose results are as yet unpublished) suggest that mean weight loss with high-protein diets during the first six months of use is approximately 20 pounds. While this weight-loss is greater than that which occurs from diets not designed for weight loss (e.g., diets based on the Food Guide Pyramid or National Cholesterol Education Program guidelines), it is not demonstrably greater than that which occurs with other weight-loss regimens or with low-fat, vegetarian diets prescribed without energy restrictions.²

High-protein, very-low-carbohydrate weight-loss diets are designed to induce ketosis, a state that also occurs in uncontrolled diabetes mellitus and starvation. When carbohydrate intake or utilization is insufficient to provide glucose to the cells that rely on it as an energy source, ketone bodies are formed from fatty acids. An increase in circulating ketones can disturb the body's acid-base balance, causing metabolic acidosis. Even mild acidosis can have potentially deleterious consequences over the long run, including hypophosphatemia, resorption of calcium from bone, increased risk of osteoporosis, and an increased propensity to form kidney stones.³

High-protein diets typically skew nutritional intake toward higher-than-recommended amounts of dietary cholesterol, fat, saturated fat, and protein, and very low levels of fiber and some other protective dietary constituents. The Nutrition Committee of the Council on Nutrition, Physical Activity, and Metabolism of the American Heart Association states, “High-protein diets are not recommended because they restrict healthful foods that provide essential nutrients and do not provide the variety of foods needed to adequately meet nutritional needs. Individuals who follow these diets are therefore at risk for compromised vitamin and mineral intake, as well as potential cardiac, renal, bone, and liver abnormalities overall.”⁴

A nutrient analysis of the sample menus for the three stages of the Atkins diet as described in Dr. Atkins' New Diet Revolution (pp. 257-259), using Nutritionist V, Version 2.0, for Windows 98 (First DataBank Inc., Hearst Corporation, San Bruno, CA) is presented below. The menus analyzed were as follows:

Typical Induction Menu

Breakfast

Bacon slices, 4 slices
Coffee, decaf, 8 ounces
Scrambled eggs, 2

Lunch

Bacon cheeseburger, no bun
 

Small tossed salad, no dressing
Seltzer water

Dinner

Shrimp cocktail, 3 ounces
Mustard, 1 teaspoon
Mayonnaise, 1 tablespoon
Clear consommé, 1 cup
T-bone steak, 6 ounces
Tossed salad
Russian dressing
Sugar-free Jell-O, ½ cup
Whipped cream, 1 tablespoon

Typical Ongoing Weight Loss Menu

Breakfast

Western Omelet
 

Tomato juice, 3 ounces
Crispbread, 2 carbo grams (1/4 slice)
Tea, decaf, 8 ounces

Lunch

Chef's salad with ham, cheese, and egg with zero-carb dressing
Iced herbal tea, 8 ounces

Dinner

Subway seafood salad, 1 item
Poached salmon, 6 ounces
Boiled cabbage, 2/3 cup
Strawberries, ½ cup with 4 tablespoons cream

Typical Maintenance Menu

Breakfast

Gruyère and spinach omelet
 

½ cantaloupe
Crispbread, 4 carbo grams, ½ slice
Coffee, decaf, 8 ounces

Lunch

Roast chicken, 6 ounces
Broccoli, 2/3 cup, steamed
Green salad
Creamy garlic dressing
Club soda

Dinner

French onion soup, 1 cup
Salad with tomato, onion, carrots
Oil and vinegar dressing
Asparagus, 1 cup
Baked potato, ½ small with sour cream (2 tablespoons) and chives
Veal chops, 1 serving
Fruit compote, 1¼ cups (generous cup)
Wine spritzer, 16 ounces

Nutrient Analysis of Atkins Sample Diets

The nutritional analysis shows that the sample menus do not meet recommended dietary intakes for macronutrients. In addition to very high protein content and low carbohydrate content, the menus at all three stages are very high in saturated fat (Daily Value is <20 g) and cholesterol (DV <200 mg) and very low in fiber (DV > 25 g). In addition, these sample menus do not reach daily values for iron. The Induction menu does not meet the daily values for calcium, vitamin C, vitamin A, folate, and thiamin. The Weight Loss menu is low on calcium, folate, and thiamin.

High-protein, high-fat dietary patterns, when followed over the long term, are associated with increased risk of the following conditions:

1. Colorectal cancer. Colorectal cancer is one of the most common forms of cancer and is among the leading causes of cancer-related mortality. Long-term high intake of meat, particularly red meat, is associated with significantly increased risk of colorectal cancer. The 1997 report of the World Cancer Research Fund and American Institute for Cancer Research, Food, Nutrition, and the Prevention of Cancer, reported that, based on available evidence, diets high in red meat were considered probable contributors to colorectal cancer risk. Proposed mechanisms for the observed association include the effect of dietary fat on bile acid secretion, the action of cholesterol metabolites within the colonic lumen, and the carcinogenic action of heterocyclic amines produced during the cooking process, among others. In addition, high-protein diets are typically low in dietary fiber. Fiber facilitates the movement of wastes, including intralumenal carcinogens, out of the digestive tract, and promotes a biochemical environment within the colon that appears to be protective against cancer.⁵

2. Cardiovascular disease. Typical high-protein diets are extremely high in dietary cholesterol and saturated fat. The effect of such diets on serum cholesterol concentrations is a matter of ongoing research. However, such diets pose additional cardiovascular risks, including increased risk for cardiovascular events immediately following a meal. Evidence indicates that meals high in saturated fat impair arterial compliance, increasing the risk of cardiovascular events in the postprandial period. A recent study showed that the consumption of a high-fat meal (ham-and-cheese sandwich, whole milk, and ice cream) reduced systemic arterial compliance by 25% at 3 hours and 27% at 6 hours.⁶

3. Impaired renal function. High-protein diets are associated with impairments in renal function. Over time, individuals who consume large amounts of protein, particularly animal protein, risk significant kidney damage.

The American Academy of Family Physicians notes that high animal protein intake is largely responsible for the high prevalence of kidney stones in the United States and other developed countries and recommends protein restriction for the prevention of recurrent nephrolithiasis.⁷ In part, this is because protein ingestion increases renal acid secretion, calcium resorption from bone, and a reduction in renal calcium resorption. In addition, animal protein is a major dietary source of purines, the major precursors of uric acid, an important factor in some stone formers. When uric acid builds up, especially in an acid environment, it can precipitate in uric acid stone formers, and decrease the solubility of calcium oxalate, a problem for calcium stone formers.⁷

4. Osteoporosis. Elevated protein intake is known to encourage urinary calcium losses and has been shown to increase risk of fracture in cross-cultural and prospective studies.^8,9 When carbohydrate is limited and a ketotic state is induced, this effect is magnified by the metabolic acidosis produced.³

5. Complications of diabetes. In diabetes, renal impairment and cardiovascular disease are particularly common. The use of diets that may further tax the kidneys and may reduce arterial compliance is not recommended. Furthermore, contrary to some news reports, diets high in complex carbohydrates and low in fat do not impair glucose tolerance; most evidence indicates that such diets improve insulin sensitivity.

In individuals with diabetes, the principal strategies for preventing or slowing impairment of renal function include controlling blood glucose levels, blood pressure, and hyperlipidemia, and decreasing protein intake to low normal levels. The beneficial effect of low-protein diets in diabetic nephropathy has been confirmed in two recent meta-analyses, with no adverse effects on the glycemic control.¹⁰

While high-protein diets may carry potential health risks for anyone if maintained for more than a few weeks, they are clearly contraindicated for individuals with recurrent kidney stones, kidney disease, diabetes, osteoporosis, colon cancer, or heart disease.

Misunderstandings and Deceptive Statements

Recent prominent news stories have encouraged the circulation of significant misunderstandings among members of the public, sometimes further encouraged by inaccurate information produced in the course of media interviews. Some patients may be confused or misled about important dietary issues based on the following inaccurate notions:

1. “High-protein diets cause dramatic weight loss.”

As noted above, the weight loss typically occurring with high-protein diets—approximately 20 pounds over the course of six months—is not demonstrably different from that seen with other weight-reduction regimens or with low-fat, vegetarian diets. Anecdotal accounts of greater weight loss are atypical and may represent the additional effects of exercise or other factors.

2. “Fatty foods must not be fattening, because fat intake fell during the 1980s, just as America's obesity epidemic began.”

Some news stories have encouraged the public to discount health warnings about dietary fat and saturated fat, suggesting that fat intake declined during the 1980s, an era during which obesity became more common. However, food surveys from the National Center for Health Statistics from 1980 to 1991 show that daily per capita fat intake did not drop during that period. For adults, fat intake averaged 81 grams in 1980 and rose to 86 grams in 1991. While the American public added sodas and other non-fat foods to the diet, forcing the percentage of calories from fat to decline slightly, the actual amount of fat in the American diet steadily climbed.

A notable contributor to the increased fat intake during that period was a dramatic increase in cheese consumption. Per capita cheese consumption rose from 15 pounds in 1975 to more than 30 pounds in 1999. Typical cheeses derive approximately 70 percent of energy from fat and are a significant source of dietary cholesterol.

3. “Fat and cholesterol have nothing to do with heart problems.”

Abundant evidence has established the ability of dietary fat and cholesterol to increase cardiovascular disease risk. Nonetheless, some popular-press articles have suggested that evidence supporting this relationship is weak and inconsistent. In addition, widely circulated news reports of a myocardial infarction recently suffered by diet-book author Robert Atkins have suggested that neither diet nor atherosclerosis played any role in the unfortunate event. The net result of such reporting may be to suggest that individuals may disregard well-established contributors to heart disease.

4. “Meat doesn't boost insulin; only carbohydrates do, and that's why they make people fat.”

Popular books and news stories have encouraged individuals to avoid carbohydrate-rich foods, suggesting that high-protein foods will not stimulate insulin release. However, contrary to this popular myth, proteins stimulate insulin release, just as carbohydrates do. Clinical studies indicate that beef and cheese cause a bigger insulin release than pasta, and fish produces a bigger insulin release than popcorn.¹¹

5. “People who eat the most carbohydrates tend to gain the most weight.”

Popular diet books point out that a carbohydrate restriction may induce ketosis as well as a reduction in energy intake, resulting in temporary weight loss. This has been misinterpreted as suggesting that carbohydrate-rich foods are the cause of obesity. In epidemiologic studies and clinical trials, the reverse has been shown to be true. Many people throughout Asia consume large amounts of carbohydrate in the form of rice, noodles, and vegetables, and they generally have lower body weights than Americans—including Asian Americans—who eat large amounts of meat, dairy products, and fried foods. Similarly, vegetarians, who generally follow diets rich in carbohydrates, typically have significantly lower body weights than omnivores.

Legal Liability

Given the possibility of health risks that may occur with long-term use of high-protein diets, clinicians who prescribe such diets may put themselves into a position of potential legal liability.

High-Protein Diet Registry Established

In order to assist consumers and consulting clinicians, the Physicians Committee for Responsible Medicine has established a registry for individuals who have elected to follow high-protein diets or have been prescribed them by practitioners. Individuals signing onto the registry can report their experience with such diets and will find information on medical research and on legal issues that may relate to liability.You may refer patients to this resource at www.AtkinsDietAlert.org.

Literature cited:

1. Westman EC, Yancy WS, Edman JS, Tomlin KF, Perkins CE. Effect of 6-month adherence to a very low carbohydrate diet program. Am J Med 2002;113:30-6.
2. Ornish D, Brown SE, Scherwitz LW, Billings JH, Armstrong WT, Ports TA. Can lifestyle changes reverse coronary heart disease? Lancet 1990;336:129-33.
3. Wiederkehr M, Krapf R. Metabolic and endocrine effects of metabolic acidosis in humans. Swiss Med Wkly 2001;131:127-32.
4. St Jeor ST, Howard BV, Prewitt TE, Bovee V, Bazzarre T, Eckel RH; Nutrition Committee of the Council on Nutrition, Physical Activity, and Metabolism of the American Heart Association. Dietary protein and weight reduction: a statement for healthcare professionals from the Nutrition Committee of the Council on Nutrition, Physical Activity, and Metabolism of the American Heart Association. Circulation 2001;104:1869-74.
5. World Cancer Research Fund/American Institute for Cancer Research. Food, Nutrition, and the Prevention of Cancer: a global perspective. World Cancer Research Fund/American Institute for Cancer Research, Washington, DC, 1997, pp. 216-51.
6. Nestel PJ, Shige H, Pomeroy S, Cehun M, Chin-Dusting J. Post-prandial remnant lipids impair arterial compliance. J Am Coll Cardiol 2001;37:1929-35.
7. Goldfarb DS, Coe FL. Prevention of Recurrent Nephrolithiasis. Am Fam Physician 1999;60:2269-76.
8. Abelow BJ, Holford TR, Insogna KL. Cross-cultural association between dietary animal protein and hip fracture: a hypothesis. Calcif Tissue Int 1992;50:14-18.
9. Feskanich D, Willett WC, Stampfer MJ, Colditz GA. Protein consumption and bone fractures in women. Am J Epidemiol 1996;143:472-9.
10. Gin H, Rigalleau V, Aparicio M. Lipids, protein intake, and diabetic nephropathy. Diabetes Metab 2000 Jul;26 Suppl 4:45-53.
11. Holt SHA, Brand Miller JC, Petocz P. An insulin index of foods; the insulin demand generated by 1000-kJ portions of common foods. Am J Clin Nutr 1997;66:1264-76.

08/02/02