Guest Author - Carolyn Chambers Clark, RN, EdD
Are you on a low carb diet? Caution if you're on a low carb, high fat, high protein diet plan. Eating too much meat, fat and protein may be setting you up for kidney damage and gout, heart disease, cancer and high blood pressure.
What medical and health care provider bodies caution against low carb, high protein diets?
The American Heart Association, American Dietetic Association, and the American Kidney Fund have all published statements warning about the various dangers associated with low-carbohydrate, high-protein diets. 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."
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 kidney stones.
Who's Eating Low Carb?
Millions of Americans desperate to lose weight follow the Atkins diet or some variant of a low carb, high fat, high protein diet. Experts worry the extra protein is causing kidney stones, kidney damage, gout and more, and there is research evidence to support the concern.
What's Wrong with Low Carb and High Protein?
Low Carb diets are without the protection of the "good" carbs, the complex carbohydrates (plenty of fruits, vegetables, and grains). An extended stay on this kind of menu could spell trouble.
Diane R. Javelli, a clinical dietitian with the University of Washington says the Low Carb diets call for triple the recommended daily allowance, nearly 200 grams of protein. Javelli says Americans need greater diversity in their diet, including more fruits and vegetables. High-protein, low-carbohydrate diets tend to do just the opposite.
The Nutrition Desk Reference (Keats Publishing, 1995) states that the recommended daily allowance for protein is 50 - 60 grams of protein a day, and cautions that if you're eating more than that, it may be taxing your kidneys and the excess protein you're eating can be converted to fat.
Research Findings that Low Carb, High Protein Diets Can Damage the Kidneys
In one study, researchers from Harvard University looked at protein intakes of more than 1,600 older women. They also evaluated the women's kidney function using a measurement called the glomerular filtration rate, or GFR. Dietary protein had no significant effect on kidney function in women who had normal kidney function at the start of this study. However, in women with mild impairment of kidney function, a higher total protein intake (median of 92 grams per day, compared to 61 grams per day) was associated with a faster decline in kidney function. This was especially true for protein from meat, fish, poultry, and eggs, but not for plant proteins. These results certainly suggest that women with some impairment of kidney function should avoid high protein diets and that there may advantages to use of plant proteins as compared to animal proteins.
A second study looked at both men and women, aged 20 to 80 years. This time microalbuminuria was measured. Microalbuminuria refers to a small increase in albumin, a protein in the urine that indicates a problem with kidney function. Microalbuminuria is also associated with increased risk of stroke and heart attacks. In adults without high blood pressure or diabetes, dietary protein was not associated with microalbuminuria. Adults with both high blood pressure and diabetes, high levels of dietary protein (average intake of 111 grams per day, or about 24 percent of calories) increased the risk of having microalbuminuria. These results suggest that adults with both high blood pressure and diabetes should consider means other than high protein diets for weight loss.
Another reason for concern comes from studies of the general population, in which diets high in animal protein are associated with reduced kidney function over time. Harvard researchers reported that animal protein intake is associated with decline in kidney function, based on observations in 1,624 women participating in the Nurses' Health Study. Luckily, the damage to the kidneys was found only in those who already had reduced kidney function at the study's outset. The bad news is that as many as one in four adults in the United States may already have reduced kidney function, and the percentage is considerably higher for those over forty or who have hypertension. Mild kidney impairment is also found in approximately 40 percent of individuals with diabetes. This suggests that many people who have kidney problems are unaware of that fact and do not realize that high-protein diets may put them at risk for further deterioration.
Yet another study, this one of ten healthy participants, provided further evidence for concern. (Remember: one study never proves or disproves anything, it only provides evidence. The more studies that stack up providing evidence, the more the cause for concern.) Researchers at the University of Chicago found that those on the Low Carb High Protein diet for just six weeks had a marked increased acid load to the kidney, indicating increased risk of kidney stones, decreased estimated calcium balance (increased urinary calcium levels that was not compensated by a similar increase in intestinal calcium absorption) and may increase the risk for bone loss.
Kevin Martin, MD, directory of nephrology at St. Louis University, says the kidney changes from Low Carb eating won't show up right away. It may take a while. He warns that many people who start the Low Carb diet don't discuss it with their health care practitioner or take the time to find out the level of their kidney function and whether they may be putting themselves at risk.
Culley C. Carson, MD, chief of urology at the University of North Carolina at Chapel Hill claims he's seen a number of people with kidneys stones who were on the Atkins Low Carb diet. He says the reason is the high protein changes the acidity of the urine, leading to uric acid kidney stones.
Low Carb, High Protein Diet is Associated with Gout
The Low Carb High-Protein diet can also lead to gout according to a new study published in the New England Journal of Medicine. Various purine-rich foods and high protein intake have long been thought to be risk factors for gout. The researchers studied 47,150 men who had no history of gout at the beginning of the study. During the 12 years of the study, they documented 730 confirmed cases of gout. The relative risk of gout among men was highest among men with the highest intake of meat and seafood. They concluded that higher levels of meat and seafood consumption are associated with an increased risk of gout.
Low Carbs and High Protein also Associated with Colon Cancer, High Blood Pressure and Heart Disease, while a Diet of High Complex Carbs and Low Fat is Associated with Lower Risk For all Three.
A recent study examining death due to colon cancer tracked the consumption of fat and meat for 20 years. They found evidence that increased fat and meat intake coincided with the incidence of colon cancer. They concluded that fat and meat intake is an important determinant of colon cancer risk.
Another study used computer analysis to predict the relative benefits and potential harm for 8 popular Low Carb weight-loss diets (Atkins, Protein Power, Sugar Busters, Zone, ADA Exchange, Pritikin and Ornish.) The higher fat diets are higher in saturated fats and cholesterol than current dietary guidelines and their long-term use would increase serum cholesterol levels and risk for congestive heart disease. Higher carbohydrate, higher fiber and lower fat diets have the greatest effect in decreasing serum cholesterol and risk of congestive heart disease. While high fat diets may promote short-term weight loss, the potential hazards for worsening risk for progression of atherosclerosis (hardening of the arteries) override any short-term benefits. The computer analysis concluded that the healthiest meal plan includes low saturated fat (less meat, butter and high-fat dairy) and high in carbohydrates and fiber (fruits, vegetables and whole grains) that increase sensitivity to insulin and lower the risk for congestive heart disease.
Another study showed Low Carb and High Protein diets aren't good for blood pressure. The researchers tracked 1,710 men employed in Chicago, Illinois. Blood pressure was remeasured annually. Men who consumed 1/2 to l l/2 cups of vegetables a day and at least 1/2 cup of fruit a day reduced their risk of developing high blood pressure while men who ate beef, veal, lamb and poultry increased their blood pressure.
Low Carb, High Protein associated with Constipation
Because there is insufficient fiber (fruits, whole grains) in the low carb, high protein diet, constipation is frequently a problem. Digested food and toxins must move through the intestinal track regularly to achieve intestinal health. The lack of efficient bowel movement could explain the correlation between high protein, low carb, low fiber diets and colon cancer.
Low Carb diets can be related to fatigue and negative feelings.
Researchers at Southern Illinois University compared the psychological responses to exercise of individuals when on a Low Carb restrictive diet and when on a noncarbohydrate restrictive diet. When carbohydrates are restricted from the diet, the body's primary energy source is reduced considerably. They found that when a person restricts carbohydrates from the diet, more fatigue, more negative feeling and less positive feeling in response to exercise occurs than in individuals who are not restricting carbohydrates.
What Do Studies on Low Carb Diets Show?
Recent media reports have publicized the short-term weight loss that sometimes occurs with the use of low-carbohydrate weight-loss diets. Some of these reports have distorted medical facts and have ignored the potential risks of such diets. Past experience with the fen-phen drug combination and other weight-loss regimens has shown that some people may disregard even serious long-term health risks in hopes of short-term weight loss.
Despite anecdotal accounts of seemingly dramatic weight loss, the effect of low-carbohydrate diets on body weight is similar to that of other weight-reduction diets. In research studies at the University of Pennsylvania and at the Philadelphia Veterans Affairs Medical Center, the average participant lost weight during the first six months on the diet, but regained some of this weight during the next six months so that the net weight loss after one year (15.8 pounds in the University of Pennsylvania study and 11.2 pounds in the VA study) was not significantly different from that seen with other diets used for comparison. This degree of weight loss is not greater than that which occurs with programs using low-fat, vegetarian diets. In Dean Ornish's program for reversing heart disease, for example, a combination of a low-fat, vegetarian diet and exercise led to an average weight loss of 22 pounds in the first year, along with dramatic reductions in cholesterol levels and reversal of existing heart disease. Five years later, much of that benefit had been retained. Studies of whether weight loss from low-carbohydrate diets is maintained for more than one year have not been performed.
A review of 107 research studies on various low-carbohydrate, high-protein weight-loss diets concluded that weight loss on these diets is not due to any special effect of restricting carbohydrate. Weight loss depended on the extent to which the dieters' caloric intake fell and how long they continued with their regimens. Other reports have also found calorie reduction to be the most important factor in weight loss, with no special weight-loss advantage from the restriction of carbohydrates.
Some low-carbohydrate diet books, such as those promoting the Atkins diet, describe how a diet devoid of carbohydrate forces the body to turn to other fuels for energy. That means getting energy from fats and protein in the diet or from body fat. When fats in the diet or in body fat are used for energy, they produce compounds called ketones, and low-carbohydrate dieters sometimes check for the presence of ketones in their urine as a sign that they have managed to eliminate carbohydrate. It turns out, however, that, in controlled trials, the degree of ketosis does not appear to influence weight-loss speed.
Devotees of the low carb, high protein diet claim it is safe as long as people drink six to eight glasses of water a day. Dr. Carson reports his patients and he himself find it difficult to drink so much water. Even if people can drink that much water a day, that might only protect against kidney stones, but it is unknown whether the additional water protects against gout, bone loss and acid load to the kidney
No published studies have addressed the long-term effects of low-carbohydrate diets. The longest studies have followed dieters for only 12 months, which is not sufficient to assess whether dieters are at risk for the problems seen in studies of general populations consuming large amounts of meat, fatty dairy products, and the cholesterol, saturated fat, and animal protein they contain.
Low Carb, High Protein diets don't follow principles for long-term weight loss.
Anyone can lose weight short-term on most diets, including a Low Carb, High Protein diet, but yo-yo dieting (losing and regaining weight) can be dangerous and frustrating. Long-term weight loss is most consistently achieved by eating a fat-restricted diet abundant in whole grains, vegetables and fruit, along with regular physical activity.
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