Misunderstandings and Deceptive Statements- Health Risks of High-Protein Diets

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Misunderstandings and Deceptive Statements

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

 

 

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.

 

 

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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. Three recent studies (one at Duke

University1, a second at the University of Pennsylvania2, and a

third at a Philadelphia medical center3) 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.4 A recent review of

107 research studies on high-protein, low-carbohydrate weight-loss

diets found that the amount of carbohydrate in the diet had no

effect on the degree of weight loss, although those individuals

following their diets for longer periods had greater weight loss.5

 

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.6

 

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. " 7

 

 

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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, 1 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, 1 cup with 4 tablespoons cream

 

 

Typical Maintenance Menu

Breakfast

Gruyere and spinach omelet:

Eggs, 2

Gruyere cheese, 2 ounces

Spinach, 1/4 cup cooked

Butter, 1 tablespoon

1 cantaloupe

Crispbread, 4 carbo grams, 1 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, 1 small with sour cream (2 tablespoons) and chives

Veal chops, 1 serving

Fruit compote, 1+ cups (generous cup)

Wine spritzer, 16 ounces

 

 

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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, 5g (% 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.

 

 

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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.8

 

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. In a small study, individuals following high-protein diets

against medical advice showed increases in fibrinogen, lipoprotein

(a), and C-reactive protein, and demonstrable progression of

coronary artery disease, suggesting that high-protein diets may

precipitate progression of CAD through increases in lipid deposition

and inflammatory and coagulation pathways.9 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 percent at 3 hours and 27

percent at 6 hours.9

 

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

permanent loss of kidney function. Harvard researchers reported

recently that high-protein diets were associated with a significant

decline in kidney function, based on observations in 1,624 women

participating in the Nurses' Health Study. The damage was found only

in those who already had reduced kidney function at the study's

outset; however, as many as one in four adults in the United States

may already have reduced kidney function. Many patients who have

renal problems may be unaware of this fact and do not realize that

high-protein diets may put them at risk for further deterioration.

The kidney-damaging effect was seen only with animal protein. Plant

protein had no harmful effect.10

 

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.11 In part, this is because protein ingestion

increases renal acid secretion and calcium resorption from bone and

reduces 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.12

 

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.9,10 When

carbohydrate is limited and a ketotic state is induced, this effect

is magnified by the metabolic acidosis produced.3 In a 2002 study of

10 healthy individuals who were put on a low-carbohydrate, high-

protein diet for six weeks under controlled conditions, urinary

calcium losses increased 55 percent (from 160 to 248 mg/d, P <

0.01).13 The researchers concluded that the diet presents a marked

acid load to the kidney, increases the risk for kidney stones, and

may increase the risk for bone loss.

 

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; in fact, 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.14

 

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.

 

 

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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 was essentially unchanged 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 did not drop

at all.

 

A notable contributor to fat intake during that period was 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 cardiac arrest suffered by the late

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.13

 

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

epidemiological 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.

 

 

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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.

 

 

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References:

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. Foster GD, et al. A randomized trial of a low-carb diet for

obesity. N Engl J Med 2003;348:2082-90.

3. Samaha FF, et al. A low-carbohydrate as compared with a low-fat

diet in severe obesity. N Engl J Med 2003;348:2074-81.

4. Ornish D, Brown SE, Scherwitz LW, Billings JH, Armstrong WT,

Ports TA. Can lifestyle changes reverse coronary heart disease?

Lancet 1990;336:129–33.

5. Bravata DM, Sanders L, Huang J, et al. Efficacy and safety of low-

carbohydrate diets: a systematic review. JAMA 2003;289:1837-50.

6. Wiederkehr M, Krapf R. Metabolic and endocrine effects of

metabolic acidosis in humans. Swiss Med Wkly 2001;131:127–32.

7. 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.

8. 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.

9. Fleming RM. The effect of high-protein diets on coronary blood

flow. Angiology 2000 Oct;51(10):817–26.

10. Knight EL, Stampfer MJ, Hankinson SE, Spiegelman D, Curhan GC.

The Impact of Protein Intake on Renal Function Decline in Women with

Normal Renal Function or Mild Renal Insufficiency Ann Int Med

2003;138:460-7.

11. 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.

12. Goldfarb DS, Coe FL. Prevention of Recurrent Nephrolithiasis. Am

Fam Physician 1999;60:2269–76.

13. 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.

14. Feskanich D, Willett WC, Stampfer MJ, Colditz GA. Protein

consumption and bone fractures in women. Am J Epidemiol 1996;143:472–

9.

15. Reddy ST, Wang CY, Sakhaee K, Brinkley L, Pak CY. Effect of low-

carbohydrate high-protein diets on acid-base balance, stone-forming

propensity, and calcium metabolism. Am J Kidney Dis 2002;40:265–74.

16. Gin H, Rigalleau V, Aparicio M. Lipids, protein intake, and

diabetic nephropathy. Diabetes Metab 2000 Jul;26 Suppl 4:45–53.

17. 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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