From Wikipedia, the free encyclopedia - View original article
|Author||T. Colin Campbell, Ph.D. and Thomas M. Campbell II, M.D.|
|Pages||417 (first edition)|
|Followed by||Whole: Rethinking the Science of Nutrition (2013)|
|Author||T. Colin Campbell, Ph.D. and Thomas M. Campbell II, M.D.|
|Pages||417 (first edition)|
|Followed by||Whole: Rethinking the Science of Nutrition (2013)|
The China Study is a book by T. Colin Campbell, Jacob Gould Schurman Professor Emeritus of Nutritional Biochemistry at Cornell University, and his son Thomas M. Campbell II, a physician. It was first published in the United States in January 2005 and had sold over one million copies as of October 2013, making it one of America's best-selling books about nutrition.
The China Study examines the relationship between the consumption of animal products (including dairy) and chronic illnesses such as coronary heart disease, diabetes, and cancers of the breast, prostate and bowel. The authors conclude that people who eat a whole-food, plant-based/vegan diet—avoiding all animal products, including beef, pork, poultry, fish, eggs, cheese and milk, and reducing their intake of processed foods and refined carbohydrates—will escape, reduce or reverse the development of numerous diseases. They write that "eating foods that contain any cholesterol above 0 mg is unhealthy."
They also recommend sunshine exposure or dietary supplements to maintain adequate levels of vitamin D, and supplements of vitamin B12 in case of complete avoidance of animal products. They criticize low-carb diets, such as the Atkins diet, which include restrictions on the percentage of calories derived from complex carbohydrates. They are also critical of reductionist approaches to the study of nutrition, whereby certain nutrients are blamed for disease, as opposed to studying patterns of nutrition and the interactions between nutrients.
The book is loosely based on the China-Cornell-Oxford Project, a 20-year study – described by The New York Times as "the Grand Prix of epidemiology" – conducted by the Chinese Academy of Preventive Medicine, Cornell University and the University of Oxford. T. Colin Campbell was one of the study's directors. It looked at mortality rates from cancer and other chronic diseases from 1973–75 in 65 counties in China; the data was correlated with 1983–84 dietary surveys and blood work from 100 people in each county. The research was conducted in those countries because they had genetically similar populations that tended, over generations, to live and eat in the same way in the same place. The study concluded that counties with a high consumption of animal-based foods in 1983–84 were more likely to have had higher death rates from "Western" diseases as of 1973–75, while the opposite was true for counties that ate more plant foods.
The authors argue that "most, but not all, of the confusion about nutrition is created in legal, fully disclosed ways and is disseminated by unsuspecting, well-intentioned people, whether they are researchers, politicians or journalists," and that there are powerful industries that stand to lose a lot if Americans shift to a plant-based diet. They write that those industries "do everything in their power to protect their profits and their shareholders."
They argue that earlier studies of nutrition (particularly the well-known Nurses' Health Study, which began in 1976) were flawed because they focused on the effects of varying amounts of individual nutrients among people who were consuming a uniformly carnivorous (animal-based) diet. They write that "hardly any study has done more damage to the nutritional landscape than the Nurses' Health Study," and that it should "serve as a warning for the rest of science for what not to do."
The authors describe their eight principles of food and health:
The China-Cornell-Oxford Project—the "China-Oxford-Cornell Study on Dietary, Lifestyle and Disease Mortality Characteristics in 65 Rural Chinese Counties," referred to in the book as "the China Study"—was a comprehensive study of dietary and lifestyle factors associated with disease mortality in China. The study compared the health consequences of diets rich in animal-based foods to diets rich in plant-based foods among people who were genetically similar.
The idea for the study began in 1980–81 during discussions between T. Colin Campbell at Cornell and Chen Junshi, Deputy Director of Institute of Nutrition and Food Hygiene at the Chinese Academy of Preventive Medicine. They were later joined by Richard Peto of the University of Oxford – Professor of Medical Statistics and Epidemiology as of 2012 – and Li Junyao of the China Cancer Institute.
In 1983 two villages were chosen at random in each of 65 rural counties in China, and 50 families were chosen at random in each village. The dietary habits of one adult member of each family were examined – half male, half female – and the results compared to the death rates in those counties from around 48 forms of cancers and other diseases during 1973–75.
The study included a comparison of the prevalence of Western diseases (coronary heart disease, diabetes, leukemia, and cancers of the colon, lung, breast, brain, stomach and liver) in each county, using 1973–75 death rates. The study collected diet and lifestyle variables (ignoring all other factors) from inhabitants of the same counties approximately 10 years later, and found that, as blood cholesterol levels rose, so did the prevalence of "Western" diseases recorded in those counties in 1973–75.
The study linked lower blood cholesterol levels to lower rates of heart disease and cancer. As blood cholesterol levels decreased from 170 mg/dl to 90 mg/dl, the authors write that cancers of the liver, rectum, colon, lung, breast, childhood and adult leukemia, brain, stomach and esophagus (throat) decreased. Rates for some cancers varied by a factor of 100 from those counties with the highest rates to the counties with the lowest rates.
The authors write that "as blood cholesterol levels in rural China rose in certain counties the incidence of 'Western' diseases also increased. What made this so surprising was that Chinese levels were far lower than we had expected. The average level of blood cholesterol was only 127 mg/dl, which is almost 100 points less than the American average (215 mg/dl). ...Some counties had average levels as low as 94 mg/dl. ...For two groups of about twenty-five women in the inner part of China, average blood cholesterol was at the amazingly low level of 80 mg/dl."
The authors write that "several studies have now shown, in both experimental animals and in humans, that consuming animal-based protein increases blood cholesterol levels. Saturated fat and dietary cholesterol also raise blood cholesterol, although these nutrients are not as effective at doing this as is animal protein. In contrast, plant-based foods contain no cholesterol and, in various other ways, help to decrease the amount of cholesterol made by the body." They write that "these disease associations with blood cholesterol were remarkable, because blood cholesterol and animal-based food consumption both were so low by American standards. In rural China, animal protein intake (for the same individual) averages only 7.1 grams per day whereas Americans average 70 grams per day."
They conclude that "the findings from the China Study indicate that the lower the percentage of animal-based foods that are consumed, the greater the health benefits—even when that percentage declines from 10% to 0% of calories. So it's not unreasonable to assume that the optimum percentage of animal-based products is zero, at least for anyone with a predisposition for a degenerative disease."
Plants protect the body from disease, they argue, because many of them contain both a large concentration of and a large variety of antioxidants, which protect the body from damage caused by free radicals. Western diseases are correlated with growth, which is associated with the increased risk of initiation, promotion and progression of disease, and that growth is correlated with a diet high in animal protein. They argue that the consumption of animal protein increases the acidity of blood and tissues and that to neutralize this acid, calcium (a very effective base) is pulled from the bones. They also state that higher concentrations of calcium in the blood inhibit the process by which the body activates vitamin D in the kidneys to calcitriol, a form that helps regulate the immune system.
They argue that the risk of developing Type I diabetes is strongly correlated with the consumption of cow's milk by infants. Autoimmune diseases such as Type I diabetes, multiple sclerosis and rheumatoid arthritis have certain common features and may share the same cause or causes. They say that autoimmune diseases are more prevalent among people who live at higher geographic latitudes, and also among people who consume a diet high in animal protein, particularly cow's milk. They argue that vitamin D is plausibly connected to both of these correlations. Vitamin D is important for the proper regulation of the immune system, and that for people who live at higher geographic latitudes, a lack of exposure to ultraviolet sunlight can result in a deficiency. The consumption of animal protein, especially casein in cow's milk, results in higher concentrations of calcium in the blood, which inhibits the process by which the body activates vitamin D in the kidneys to a form that helps repress the development of autoimmune diseases.
They say that cognitive impairment and dementia, including Alzheimer's disease, are linked to hypertension, high blood cholesterol, and damage caused by free radicals, and that these risk factors can be controlled by diet.
The authors link breast cancer to the long-term exposure to higher concentrations of female hormones, which in turn is associated with early menarche (age at first menstruation), late menopause, and a high concentration of blood cholesterol. They argue that all these risk factors are linked to a diet high in animal protein, particularly casein from cow milk. The average Chinese woman is exposed to 35–40 percent of the lifetime estrogen exposure of the average British or American woman, and the rate of breast cancer among Chinese women is about one-fifth of the rate among Western women. They also argue that lower rates of colorectal cancer are associated with the consumption of plants high in fiber, such as beans, leafy vegetables and whole grains.
The authors describe a diet study conducted by James D. Anderson, M.D., of 50 patients—25 with Type I diabetes and 25 with Type II diabetes—who were taking insulin to control their blood glucose concentrations. The authors reported that after these patients switched from the American-style diet recommended by the American Diabetes Association to a high-fiber, low-fat, plant-based diet, the patients with Type I diabetes were able to reduce their insulin by an average of 40 percent within three weeks of changing their diet, and 24 of the 25 patients with Type II diabetes were able to stop taking their insulin altogether within weeks.
They argue that studies show a diet that includes carotenoids, which are found in colorful vegetables, provide protection from macular degeneration, an eye disease that can cause blindness, and that a diet that includes lutein, a particular antioxidant found in spinach, provides protection from cataracts.
They say studies show that eating plant protein has a greater power to lower cholesterol levels than reducing fat or cholesterol intake. At the time of their study, the death rate from coronary heart disease was seventeen times higher among American men than rural Chinese men. They write that "the average calorie intake per kilogram of body weight was 30 percent higher among the least active Chinese than among average Americans. Yet, body weight was 20 percent lower." The authors add that "consuming diets high in protein and fat transfers calories away from their conversion into body heat to their storage form as body fat (unless severe calorie restriction is causing weight loss.)" They argue that "diet can cause small shifts in calorie metabolism that lead to big shifts in body weight," adding that "the same low-animal protein, low-fat diet that helps prevent obesity also allows people to reach their full growth potential."
The consumption of animal protein is linked to risk factors for the formation of kidney stones. They state that increased levels of calcium and oxalate in the blood may result in kidney stones, and that recent research shows that kidney stone formation may be initiated by free radicals.
The authors state that osteoporosis is linked to the consumption of animal protein because animal protein, unlike plant protein, increases the acidity of blood and tissues. They add that to neutralize this acid, calcium (a very effective base) is pulled from the bones, which weakens them and puts them at greater risk for fracture. The authors add that "in our rural China Study, where the animal to plant ratio [for protein] was about 10 percent, the fracture rate is only one-fifth that of the U.S."
Campbell published an article in the Journal of Clinical Nutrition in 2000 in which he criticized a paper by Frank B Hu and Walter Willett based on data from the Nurses' Health Study; Campbell disagreed with its conclusion that increased consumption of animal protein is associated with decreased risk of ischemic heart disease and criticized the homogeneity of the study population and its high-animal-protein diet, and criticized the application of pharmaceutical-style analysis of individual nutrients. Hu and Willett published a reply to Campbell in the same issue, in which they defended their finding that higher animal or vegetable protein does not correlate with higher rates of ischemic heart disease, but instead correlates with slightly lower rates; they also defended the study of individual nutrients as both possible and useful. They also cited Campbell's 1990 publication of China Study against him, saying that the 1990 study "did not find a clear association between animal product consumption and risk of heart disease or major cancers." They also noted that they had advised caution with respect to giving advice to the public about the benefits of eating more protein, "because a high dietary protein intake is often accompanied by high saturated fat and cholesterol intakes." In 2010, in an article, "Healthy eating guide," Willet encouraged people to eat more proteins than carbohydrates, noted that there is no difference in the actual protein from animals and vegetables, and advised readers to choose protein "packages" such as beans, nuts, seeds, and the like, that were not high in saturated fat and cholesterol.
Wilfred Niels Arnold, professor of biochemistry at the University of Kansas Medical Center, reviewed the book in Leonardo in 2005: "Any serious challenge to the 'American Diet' is bound to elicit some academic, public, and food industry opposition ... the authors anticipate resistant and hostile sources, sail on with escalating enthusiasm, and furnish a working hypothesis that is valuable. In fact, the surprising data are difficult to interpret in any other way."
In a written debate with Campbell in 2008, Loren Cordain, a professor in the Department of Health and Exercise Science at Colorado State University, argued that "the fundamental logic underlying Campbell's hypothesis (that low [animal] protein diets improve human health) is untenable and inconsistent with the evolution of our own species", and that "a large body of experimental evidence now demonstrates a higher intake of lean animal protein reduces the risk for gout, cardiovascular disease, hypertension, dyslipidemia, obesity, insulin resistance, and osteoporosis while not impairing kidney function." Campbell responded by questioning the implications of the evidence Cordain noted, and argued that "diet-disease associations observed in contemporary times are far more meaningful than what might have occurred during evolutionary times—at least since the last 2.5 million years or so."
American President Bill Clinton became a vocal supporter of The China Study. In 2010, after years of living with heart disease, he undertook the diet, eating legumes, vegetables, fruit and a protein shake every morning, effectively living as a vegan. Within a short period he said that he had dropped 24 pounds, returning him to his college weight. Sanjay Gupta, CNN's chief medical correspondent, said in his documentary The Last Heart Attack in August 2011 that The China Study had changed the way people all over the world eat, including Gupta himself.