Chronic diseases such as heart disease, cancer, stroke or diabetes are the main causes of death in many parts of the world including both developed and developing countries. These diseases are largely the result of our lifestyles, especially smoking, a diet based on refined products, devoid of certain vitamins and mineral salts, phytochemicals and dietary fiber, excessive consumption of protein and fats of animal origin and lack of physical activity. Obesity, especially abdominal obesity, also has a major impact on the emergence of these diseases.

A healthy diet is based on a variety of unrefined plant foods that are rich in many beneficial compounds including dietary fiber, trace elements and a whole range of phytochemicals. Eating the recommended amounts of these products is associated with a reduced risk of many chronic diseases, including cardiovascular diseases, cancers, diabetes, obesity, Alzheimer’s disease, diseases of the digestive system and others. The above mentioned products can be prepare in different ways, such as bread, cereals, juices, veggie burgers, spreadable butters and others. They can be consumed raw, boiled, baked, fried and cooked.

Consumption of these products is recommended by the most prestigious health and nutrition organizations. Recommending adequate fruits, vegetables, whole grains and other plant foods intake is usually included in different dietary guidelines for disease prevention and in guidelines for specific disease management. For example, the Academy of Nutrition and Dietetics (formerly the American Dietetic Association), the Dietitians of Canada, the American Cancer Society, the American Institute for Cancer Research, the World Cancer Research Fund, the American Heart Association, the American Stroke Association, the National Institutes of Health, the American Academy of Pediatrics, United States Department of Agriculture, United States Department of Health and Human Services and many others, are promoting the consumption of whole grain products, fruits and vegetables.

Recently, a few individuals developed diets based on principles that differ diametrically from those described above. Many of them are advertised as a way to lose weight. Others promise to be the solution to many or even all of society’s health problems. Although many of these diets originate in the United States and Americans spend billions of dollars on such “solutions” to their health problems, in America, about 70 percent of adults are overweight or obese, more than 80 million have at least one type of cardiovascular disease and almost 60 million either already have or are at risk of having type 2 diabetes. Diets that promise to be the solution to people’s health problems seem to be multiplying like mushrooms. Therefore, it is almost impossible to describe each of them. The focus of this chapter is on low carbohydrate, high protein diets. These diets have been very popular in North America in the last several years.

Low carbohydrate diets became very popular in the beginning of 2000. There are at least several different low carbohydrate diets including the Zone Diet, Protein Power and the Sugar Buster. The most popular of them all is the Atkins Diet. Many of these diets originated in the United States and many have their equivalents in other countries. For example, a low carbohydrate/high protein diet in Poland is called the Optimal Diet.

The low carbohydrate/high protein dietary principle has been around since the 19th century. In America, Dr. Atkins popularized his version of the low carbohydrate/high protein diet in late 1960 and 1970 in his book entitled “Dr. Atkins’ Diet Revolution.” A revised version of this book has been published more recently as “Dr. Atkins’ New Diet Revolution.” Until recently, the Atkins Diet had been one of the most popular diets among people trying to lose weight. In the United States, in the height of its popularity it was estimated that about 1 in 11 people practiced this diet. As a result of its popularity, some companies introduced a new line of low carbohydrate products including beverages. Many restaurants have introduced new low carbohydrate meals.

However, as time progressed the popularity of the Atkins Diet fell dramatically to the point that in July 2005 the company Atkins Nutritional Company, which was owned by Dr. Atkins, declared bankruptcy. Despite the popularity of this and other similar diets, data in the United States showed that in the year 2012, approximately 70 percent of Americans were overweight or obese. The rate of obesity has been steadily increasing even during the year when low carbohydrate/high protein were the most popular.

The main assumption of the low carbohydrate/high protein diets is to consume a high amount of foods high in protein which should replace foods that are high in carbohydrates. For example, in his book Dr. Atkins recommended reducing the consumption of carbohydrates to 20 grams per day and not exceeding carbohydrates intake to more than 10 percent of total calories. Individuals who adopt low carbohydrate/high protein diets are advised to eat basically unlimited amounts of animal products such as eggs, cheese, meat (including red, white and processed meats), organ meats, fish, poultry, mayonnaise, whole milk, cream, etc. Foods that are not recommended at all or at least not recommended in large amounts include grains, including breads, rice, pasta, and cereal, fruits, fruit juices, jams, certain vegetables such as potatoes and legumes.

There are at least several reasons why low carbohydrate/high protein diets should not be recommended. First, they restrict consumption of products such as fruits, vegetables (including beans) and grains. Thousands of research in the past decades have shown that these products are associated with a lower risk of heart disease, hypertension, cancer of certain organs, diabetes, dementia (including Alzheimer’s disease) and many others (some of these studies have been described in this book). These products are routinely recommended by organizations such as the American Dietetic Association, the National Institute of Health, and the American Institute of Cancer Research as food types individuals should be encouraged to eat. Consuming high protein diets not only is not supported by any professional organization. Such diets have never been promoted for prevention of chronic health conditions such as heart disease or cancer. Furthermore, many professional organizations condemned such dietary advice warning people against their potentially detrimental consequences.

Second, these diets contribute to a higher consumption of both fat, especially saturated fat, and protein from meat and animal products. Countless research manuscripts documented that intake of these foods is associated with many health problems including those listed in the beginning of this chapter. The following comment adequately illustrates the opinion of the vast majority of health professionals regarding advising people to eat unlimited amounts of these foods. Dr. Fredrick Stare, who was the chair of the Nutrition Department at Harvard University, during the Senate meeting in 1973, commenting on Dr. Atkins’ book, said: “(…) any book that recommends unlimited amounts of meat, butter, and eggs, as this one does, in my opinion is dangerous. The author who makes the suggestion is guilty of malpractice.”

Third, high protein diets do not provide the body with an adequate amount of at least several nutritional compounds including dietary fiber and some vitamins and minerals. The quote in the article published in the Journal of the American College of Cardiology, highlights the problem: “These diets do not meet the nutritional requirements of healthy people based on the current dietary reference intakes for many vitamins and minerals and recommendations for dietary fiber. When used for weight loss, these diets are associated with several potential adverse effects and nutrient deficits, and the long-term consequences of their continued use are unknown. On the basis of evidence currently available, LC-HP (low carbohydrate/high protein – author) diets cannot be recommended as a part of a long-term care plan for weight management in patients who smoke or have common diseases that affect the cardiovascular system, such as hypertension, hyperlipidemia, diabetes mellitus, and coronary atherosclerotic vascular disease, where endothelial dysfunction is a feature.”

Fourth, low carbohydrate/high protein diets do not provide adequate amounts of carbohydrates. The main function of carbohydrates in the body is energy synthesis. Each cell of the body needs energy in order to stay alive. Both carbohydrates and fats are composed of carbon, oxygen and hydrogen. Proteins, on the other hand, also contain nitrogen. Two things result from not providing sufficient amounts of carbohydrates for energy: the body will start making its own carbohydrates from protein and protein and fats will be used for energy.

To use amino acids, which are the basic building blocks of protein, to make carbohydrates, nitrogen will first have to be split off the protein. Nitrogen is rapidly converted to ammonia, which is eventually excreted from the body as urea. Carbon, oxygen and hydrogen molecules are then used to make glucose, which is then used as an energy source. Therefore, dietary advice to limit carbohydrate intake makes absolutely no sense since when we do not provide carbohydrates with the foods we eat, the body will make carbohydrates from non-carbohydrate sources (protein). However, it must also be recognized that this making of the body’s own carbohydrates is associated with the liver’s and the kidneys’ overload to convert nitrogen into ammonia and urea in order to get rid of this toxic compound from the body.

Another side effect of not providing an adequate amount of carbohydrate is using excessive amounts of fats in energy synthesis. Due to the limited use of carbohydrates and higher than usual utilization of fats, the body starts to convert fat into compounds called ketones, also known as ketone bodies. One of the side effects of ketone synthesis is acidic breath. Ketone bodies are toxic and are associated with all sorts of health problems. For example, research published in the British Journal of Ophthalmology described two cases of vision loss by children fed a low carbohydrate diet. In the first case, this problem developed between the 43th and 56th month of life. The eye examination showed 6/24 vision in both eyes, which could not be corrected with glasses. This child also developed color blindness.

Within six weeks of giving this child a vitamin B1 supplement, vision improved to 6/12. Vitamin B1 is found in products such as cereals or beans (consumption of both of them is not recommended by the low carbohydrate diet advocates). The acidification of the organism by the ketone bodies results in a destruction of vitamin B1. In the second case, the seven-year-old girl after a year of consuming a diet that resulted in ketones had 6/36 vision in one eye and 6/24 in the second. After administration of 50 mg a day of vitamin B1, within 3 months sight had improved to 5/6 in both eyes.

Ketone bodies cause serious health problems in children born to women who ate a low carbohydrate diets during pregnancy. In one study, which estimated the effect of such diets among 122 women, researchers observed “serious neurological disorders” and lowered IQ among children.

Intake of low carbohydrate/high protein diets are associated with a variety of adverse effects such as acidic breath, constipation, headache, muscle cramps, lack of energy or feeling sick. An example of the prevalence of the above mentioned problems may be illustrated by a study published in the Annals of Internal Medicine in 2004. The experiment involved 238 people who were divided into two groups. Individuals placed in one of these two groups followed a low carbohydrate/high protein diet. In fact, the carbohydrate content was very low, providing less than 20 grams per day. This diet was composed of an unlimited amount of meat, eggs and cheese, 2 cups of vegetable salad and 1 cup of other low carbohydrate vegetables. Among these individuals 68 percent became constipated, 60 percent experienced a headache, 38 percent had acidic breath, 35 percent had muscle spasms, 25 percent felt weak, 23 percent had diarrhea and 13 percent had skin problems.

Are low carbohydrate/high protein diets effective in weight loss?

A review of research publications that described the effect of low carbohydrate/high protein diets on weight reduction showed that any decrease in body mass was attributed to reduced caloric intake not to carbohydrate restriction or ingesting high amounts of protein. One of the body’s reactions to eating very high amounts of dietary protein is a suppression of appetite. The obvious result is the consumption of less quantity of food, which means a smaller amount of consumed calories. The caloric deficit is the reason for the weight loss. Studies have additionally revealed that people lose a relatively higher amount of weight during the first few months of following a low carbohydrate/high protein diet compare to individuals who follow a low fat diet. However, this difference disappears at the end of about 12 month period.

Effect of low carbohydrate/high protein diets on disease indices

Some people who followed low carbohydrate/high protein diets noted an improvement in blood cholesterol level, blood glucose and other markers. This improvement convinced many about the health aspects of these diets. These diets’ advocates even suggested that low carbohydrate/high protein diets may be important in the prevention of cardiovascular diseases or diabetes. It must be emphasized, however, that these apparent improvements do not mean that individuals who adhere to these diets decreased their risk of cardiovascular diseases or any other chronic health condition. As it is explained below, the opposite is true. These diets increase the risk of developing these diseases in spite of the improvements of these risk factors.

Cholesterol is a substance necessary for the proper functioning of every cell of our body, particularly the brain. The human body manufactures cholesterol, especially in liver cells. Actually, the amount of cholesterol manufactured in cells often exceeds the amount ingested with foods. Individuals who adopt a low carbohydrate/high protein diet also ingest a high amount of fat and cholesterol. The high intake of ingested cholesterol causes the body to reduce the synthesis of its own cholesterol. This is why it is possible to ingest large amounts of cholesterol and saturated fat and simultaneously reduce serum cholesterol level.

It should be noticed, however, that most studies showed that low carbohydrate diets are not nearly as effective at lowering serum cholesterol as are high fiber low fat diets. For example, a study published in 2008 in the Journal of the American College of Cardiology showed that people who followed a low carbohydrate/high protein diet lowered total cholesterol level by less than 1 percent. Cholesterol reduction among those who adhered to a high carbohydrate diet was about 11 percent. Similarly, individuals in the first group reduced the LDL cholesterol level by just 1.5 percent and those in the high carbohydrate diet by more than 16 percent. The same study showed that other parameters such as blood glucose level, diastolic blood pressure, or serum insulin level were better controlled among individuals on the high carbohydrate diet.

The reason the results of the above described study may be considered more significant in comparison to the results of other studies is that both groups of people consumed the same amount of calories. As mentioned earlier, suppressed appetite is one of the body’s reactions to eating low carbohydrate/high protein diets. As a result, in many other studies designed to compare the effect of low carbohydrate/high protein versus other diets such as low fat diets, individuals in the low carbohydrate/high protein ingested fewer calories and thus, had better results.

Health effect of low carbohydrate/high protein diets

There are many problems associated with adopting low carbohydrate/high protein diets. The most important of them have to do with them increasing the risk of at least several serious health problems. Two studies described below will illustrate their health effect. In September 2009, a team of researchers from Harvard University in the United States and from Israel, published a study conducted on mice. Mice were divided into three groups. The first group was given a low carbohydrate/high protein diet. This diet provided 12 percent of calories from carbohydrates, 45 percent from protein and 43 percent from fat. The second group of mice received a diet called the Western Diet, which was supposed to reflect the diet of people living in Western countries. This diet provided 43 percent of calories as carbohydrates, 42 percent from protein and 15 percent from fat. The third group received the typical diet of mice, comprised of 65 percent of calories from carbohydrates, 20 percent from protein and 15 percent from fat.

After 12 weeks, the mice eating the low carbohydrate/high protein diet (Group 1) gained about 28 percent less weight compared to the mice in the second and third group. After six weeks of the experiment researchers examined the thickness of atherosclerotic deposits in the arteries of all three groups of the mice. “At 6 weeks, mice on the low carbohydrate/high protein diet had significantly more atheroma than mice on the western diet (5.4% vs. 2.2% respectively, (…). This difference was maintained after 12 weeks on the diets (15.3% vs. 8.8% respectively.”

Clogging of the arteries is the cause of heart disease and other cardiovascular diseases, which are the main causes of death in many countries in which people consume a Western diet. The results of this study showed that low carbohydrate/high protein diet had a worse effect on the formation of these deposits than the typical diet of people living in developed countries. What was the effect of the typical mouse diet (this diet could be described as a high carbohydrate diet) on atherosclerosis (Group 3)? “(…) chow-fed mice had minimal, although quantifiable, amounts of plaque at both 6 (0.5%) and 12 (1.3%) weeks, which was significantly less than that seen in low carbohydrate/high protein diet and western diet-fed mice.” The authors further stated that “these data demonstrate the low carbohydrate/high protein diet-fed mice developed more extensive atherosclerosis than western diet-fed mice, despite similar dietary fat and cholesterol content, and reduced weight gain.”

To examine the impact of the low carbohydrate/high protein diet on blood flow, the researchers did a surgery on the mice from group 1 and group 2. The goal of the surgery was to tie off the femoral artery in order to stop the blood flow. Normally, a reduction of a blood flow will cause the organ to grow new arteries to make up for the reduction in the blood flow, a kind of natural bypass. The blood flow was stopped for 28 days, during which time the researchers assessed the rate of growth of new blood vessels. After this period, the femoral artery was untied and the researchers measured the rate of blood flow. The results showed that the low carbohydrate diet had caused “abnormal neovascularization,” and that “recovery of perfusion after ischemia was approximately 39% less in mice on the low carbohydrate/high protein diet compared with mice on the western diet at 28 days after surgery.” The conclusion from the above described experiment was obvious: “Exacerbated atherosclerosis occurred on the LCHP diet independent of significant alterations in traditional atherogenic serum lipids, serum inflammatory markers and histological indicators of inflammatory infiltration.”

The study described above was carried out on mice. Do low carbohydrate/high protein diets have a similar effect on atherosclerosis in humans? Results of another study published in the journal Angiology in 2000 gives a clear answer. It was conducted on 26 individuals (14 men and 12 women) age from 29 to 71 years old. These individuals were divided into two groups. The first group received a diet, in which carbohydrates provide 70 percent of the calories, protein and fat provided 15 percent each, while the ratio of unsaturated to saturated fats was 2:1. Individuals in the second group consumed a low carbohydrate/high protein diet. “The overall effect seen in the high carbohydrate group was a 23% regression in the extent of CAD (coronary artery disease – author) and a 22% reduction in the severity of CAD, which was statistically significantly different from the effects seen with advancement in CAD following a high-protein diet. The overall effect seen in patients treated who followed high protein diets was a progression in the overall extent of CAD of 39.7%.”

In conclusion, eating low carbohydrate/high protein diets is associated with inadequate intake of several nutrients and undesirable side effects including constipation, acidic breath, muscle spasms and a headache. In addition, these diets are the cause of atherosclerosis and other serious health problems including kidney, bone and liver abnormalities.


About the Author

Roman Pawlak, Ph.D, RD

Ph.D, RD is an Associate Professor of Nutrition at East Carolina University in North Carolina. He is the author several books including “Forever young. Secrets of delaying aging and living disease free,” “Healthy diet without secrets,” “In defense of vegetarianism” and “I am the Lord who heals you,” and a co-author of “Vegetarian mother and her baby.”

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