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unpublished) suggest that mean weight loss with high-protein diets during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
Bacon, 2 slices
American cheese, 1 ounce
Ground beef patty, 6 ounces
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
Eggs, 2
Cheddar cheese, 2 ounces
Bell peppers, 1 tablespoon
Onion, 1 tablespoon
Ham bits, 1/10 cup
Butter, 1 tablespoon
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
Eggs, 2
Gruyère cheese, 2 ounces
Spinach, ¼ cup cooked
Butter, 1 tablespoon
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
| |
Atkins Induction |
Atkins Weight Loss |
Atkins Maintenance |
| Energy, kcal |
1759 |
1505 |
2173 |
| Protein, g (% energy) |
143 (33%) |
120 (32%) |
135 (25%) |
| Carbohydrate, g (% energy) |
15 (3%) |
36 (10%) |
116 (22%) |
| Fat, g (% energy) |
125 (64%) |
97 (58%) |
110 (45%) |
| Alcohol, g (% energy) |
0 |
0 |
26 (8%) |
| Saturated fat, g |
42 |
45 |
38 |
| Cholesterol, mg |
886 |
885 |
834 |
| Fiber, g |
2 |
7 |
18 |
| Calcium, mg (% DV) |
373 (37%) |
952 (95%) |
1019 (102%) |
| Iron, mg (% DV) |
15 (86%) |
10 (54%) |
13 (70%) |
| Vitamin C (% DV) |
20 (33%) |
140 (234%) |
242 (404%) |
| Vitamin A, RE (% DV) |
799 (80%) |
1525 (153%) |
2521 (252%) |
| Folate, µg (% DV) |
143 (36%) |
268 (67%) |
584 (146%) |
| Vitamin B-12, µg (% DV) |
11 (191%) |
8 (132%) |
5 (80%) |
| Thiamin, mg (% DV) |
0.7 (48%) |
1.1 (76%) |
1.0 (64%) |
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
dietsapproximately 20 pounds over the course of six monthsis 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
Americansincluding Asian Americanswho 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:
- 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.
- Ornish D, Brown SE, Scherwitz LW, Billings JH, Armstrong WT, Ports TA.
Can lifestyle changes reverse coronary heart disease? Lancet
1990;336:129-33.
- Wiederkehr M, Krapf R. Metabolic and endocrine effects of metabolic
acidosis in humans. Swiss Med Wkly 2001;131:127-32.
- 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.
- 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.
- 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.
- Goldfarb DS, Coe FL. Prevention of Recurrent Nephrolithiasis. Am Fam
Physician 1999;60:2269-76.
- 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.
- Feskanich D, Willett WC, Stampfer MJ, Colditz GA. Protein consumption
and bone fractures in women. Am J Epidemiol 1996;143:472-9.
- Gin H, Rigalleau V, Aparicio M. Lipids, protein intake, and diabetic
nephropathy. Diabetes Metab 2000 Jul;26 Suppl 4:45-53.
- 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.
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