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
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.
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 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.
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, Low-Carbohydrate Diet Victims and Survivors
Jody Gorran of Delray Beach, Florida
This 53-year-old businessman had a healthy heart and no medical problems before he began a high-protein, low-carbohydrate diet. A heart scan conducted six months prior to Gorran embarking on the diet revealed no plaque or occlusions. But after more than two years on the low-carbohydrate diet, he began experiencing angina. Gorran discovered that his cholesterol had shot from a pre-diet level of 146 to 230. An angiogram showed a severe artery blockage, and Gorran underwent angioplasty. His cardiologist told him that he could have died. ?[This diet] gave me heart disease,? Gorran said.
Rachel Huskey of Sturgeon, Missouri
In August of 2000, this 16-year-old high school student collapsed in her history class and died. The probable cause of death was a high-protein, low-carbohydrate diet, according to her doctors. Huskey, who had no known medical conditions, learned about the diet from videotapes purchased from a television advertisement. She followed the diet closely, eating meat, cheese, and other high-fat foods. A post-mortem examination of Huskey revealed low calcium and potassium levels in her blood. According to Dr. Paul Robinson, an assistant professor of child health at the University of Missouri, Columbia, those depletions disrupted Huskey?s normal cardiac functions and caused her heart to stop. Those depletions, Dr. Robinson said, were most likely caused by her adherence to a high-protein, low-carbohydrate diet.
Mari K. Madlem of Claremont, California
This 51-year-old hairstylist began a high-protein, low-carbohydrate diet in May of 1998. She was on the diet for six months. Before starting the diet, her cholesterol level was 160. It went up to 258 while she was on the diet. Madlem also experienced kidney stones and had her gall bladder removed.
) is that when net carb-to-protein is brought below 1:1, then that's when you start having problems with constipation tied to the higher protein consumption. (The upper limit of 1.4 I got from research results.)