Overall score 64 Scientific accuracy 48 Reference accuracy 85 Healthfulness 58 How hard would it be to apply the book's advice? Very difficult

Summary

The China Study contends that many of our health problems--particularly cancer and coronary heart disease-- are due to a diet high in animal foods, fats, and refined carbohydrates. The book is more scholarly and thoroughly referenced than most diet/health books, perhaps not surprising considering that its primary author, T. Colin Campbell, PhD, is an accomplished diet/health researcher (its co-author is his son Thomas Campbell, II, MD). The solution to our health problems, the book contends, is a low-protein, very-low-fat, very-high-carbohydrate diet that is based entirely on unrefined plant foods: fruits, vegetables, tubers, beans, whole grains, and limited nuts, but no meat, dairy, eggs, added fats or sugars, or processed foods. The diet is intended to promote overall health in the general population, and particularly to reduce the risk of chronic diseases such as cancer and coronary heart disease. The China Study also spends a fair amount of time discussing real and perceived bias and conflicts of interest in academia, medicine, and government dietary guidelines. We evaluated three of the book’s key scientific claims and found that they were not very well supported overall. After consulting the original data and having it analyzed by a professional statistician, we conclude that a large study in China that The China Study is named after does not support the book’s claims. We did find the claim that a whole food plant-based diet reduces the risk of cardiovascular disease fairly convincing. The China Study generally cites references accurately and this is reflected in its high reference accuracy score. It received a middling score for healthfulness because although the diet will likely reduce the risk of obesity and some chronic diseases, it may also increase the risk of nutrient deficiencies unless carefully composed. The diet would be difficult to implement and maintain for most people due to its extreme nature, yet it may be worth considering for people at high risk of cardiovascular disease.

Book published in 2016 Published by BenBella Books Revised and expanded Edition, Paperback Review posted June 29, 2019 Primary reviewer: Stephan Guyenet Peer reviewer: Travis Masterson

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Introduction

The China Study contends that many of our health problems are due to a diet high in animal foods, fats, and refined carbohydrates, and the antidote is to consume a whole food, plant-based diet. More specifically, it recommends a low-protein, very-low-fat, very-high-carbohydrate diet that is based entirely on unrefined plant foods: fruits, vegetables, tubers, beans, whole grains, and limited nuts, but no meat, dairy, eggs, added fats or sugars, or processed foods. The diet is intended to promote overall health in the general population, and particularly to reduce the risk of chronic diseases such as cancer and coronary heart disease. The book also spends a fair amount of time discussing real and perceived bias and conflicts of interest in academia, medicine, and government dietary guidelines. We chose to review it because it is a very popular and influential book in the diet/health community, and we have not yet reviewed a book focused on plant-based diets.

Scientific Accuracy

We evaluated three key claims of The China Study:

Animal foods such as dairy and meat are a major cause of cancer, particularly due to the type of protein they contain. Animal foods are a major cause of cardiovascular disease. A whole food, plant-based diet prevents and reverses cardiovascular disease.

The book received an overall scientific accuracy score of 1.9, indicating that its scientific claims are not very well supported. However, this varied greatly between the three claims we evaluated. We found little compelling evidence to support the claim that animal protein in general causes cancer, somewhat more evidence to support the claim that animal foods contribute to cardiovascular disease, and fairly compelling evidence that a whole food, plant-based diet prevents and reverses cardiovascular disease.

Although one of the authors of The China Study, Campbell Sr., was involved in generating much of the science that underlies the book’s claims, upon close inspection, we found that this evidence was often represented inaccurately in the book. In particular, the large observational study in China the book is named after does not support the central claims of the book. We confirmed this by consulting the original data at the University of Washington medical library and analyzing it with the help of a professional statistician, Karl Kaiyala, PhD. In addition, The China Study omits important evidence that undermines its claim that animal protein but not plant protein increases cancer risk in rodents.

That said, there is fairly convincing evidence from randomized controlled trials and basic science research that a whole food, plant-based diet reduces the risk of cardiovascular disease. However, it remains unclear whether the observed effects are due to reducing intake of animal foods per se, vs. other diet changes like reducing intake of refined carbohydrates or greater fiber intake. The China Study tends to accurately cite this evidence, but sometimes withholds important caveats about the weakness of certain study designs, including that the China Study itself uses a study design that cannot yield confident conclusions about diet-health relationships.

See Scoring for Scientific Accuracy

Reference Accuracy

We randomly selected ten references, looked them up, and evaluated whether they convincingly supported the claims made in The China Study. The book fared relatively well in reference accuracy, netting a score of 3.4 out of 4. References generally supported the claims they were associated with. The only major exception is the claim that “vegetarians consume the same amount or even significantly more calories than their meat-eating counterparts, and yet are still slimmer” (page 131), which was not well supported by the reference cited.

See Scoring for Reference Accuracy

Healthfulness

The China Study recommends a low-protein, low-fat, high-carbohydrate diet that is based entirely on unrefined plant foods: fruits, vegetables, tubers, beans, whole grains, and limited nuts, but no meat, dairy, eggs, added fats or sugars, or processed foods. The diet is intended to promote overall health to the general public. It makes the specific claim that it can reduce the risk of chronic diseases such as cancer and coronary heart disease. We gave the whole food plant-based diet suggested by The China Study an overall healthfulness score of 2.3 out of 4.

See Scoring for Healthfulness

long-chain omega-3 fatty acids, Summary of the health-related intervention promoted in the book We believe the diet is likely to mostly achieve its goal of reducing the risk of obesity and coronary heart disease. However, the evidence that it reduces cancer risk is not compelling. Its best application may be in improving cardiovascular health in people who are at high risk of heart attack and stroke. Yet the diet may harm health in other ways due to an increased risk of nutrient deficiencies including iron zinc , and iodine . It may be possible to achieve nutrient adequacy on this diet, but it requires careful planning that is beyond the scope of the information provided to the reader in The China Study, requiring the reader to purchase additional books from the authors. The China Study recommends a diet that is based entirely on unrefined plant foods: fruits, vegetables, tubers, beans, whole grains, and limited nuts, but no meat, dairy, eggs, added fats or sugars, or processed foods. The book initially suggests that reducing intake of animal products and processed foods will be sufficient to provide general health benefits. We note that such advice is common in the general nutritional science and dietetics community. The China Study goes far beyond this by prescribing a much stricter diet regimen that is low in protein (10 percent; all from plant sources), very low in fat (10 percent), and very high in carbohydrate (80 percent). The book refers to this as a “whole food, plant-based diet.” It is important to note that this specific diet differs substantially from the distribution of protein, fat, and carbohydrate that is typically observed in people who follow a vegan diet, as highlighted within the book itself. The China Study also recommends taking a vitamin B12 supplement, a nutrient found only in animal foods, and vitamin D for people who don’t get much sun (pages 235-238). Condition targeted by the book, if applicable The China Study aims to improve general health, but particularly common chronic diseases/disorders like coronary heart disease, diabetes, obesity, and cancer. Apparent target audience of the book The China Study appears to be written for a general audience. Criterion 3.1. Is the intervention likely to improve the target condition? 3 out of 4 The intervention received a score of 3, indicating that it is likely to moderately improve its targeted conditions. We previously reviewed evidence that it will probably reduce cardiovascular risk. It will also probably cause weight loss in people with excess weight, as demonstrated by randomized controlled trials of whole food plant-based diets. Weight loss will improve metabolic health more generally, again as demonstrated by randomized controlled trials of whole food plant-based diets. However, weight loss can be achieved through a variety of dietary and lifestyle changes. It’s not clear how much weight loss this diet causes relative to others, or how much of its health benefits are attributable to the weight loss it causes. Additionally, we aren’t aware of compelling evidence that this diet reduces cancer risk, which is a central claim of the book. Criterion 3.2. Is the intervention likely to improve general health in the target audience? 3 out of 4 The intervention received a score of 3, indicating that it is likely to moderately improve general health. We have little doubt that the diet will reduce chronic disease risk overall, so in that sense it should improve general health. However, good health is a broader concept than simply avoiding disease. It includes maximizing cognitive, emotional, physical, immune, and reproductive health, and supporting development and resilience. Also, how hard it is to stick with a diet in the long run should be considered. This is where we have greater concerns about the diet recommended by The China Study. Humans have an evolutionary history eating animal foods that stretches back at least 2.6 million years, which may be why our bodies require a vitamin (B12) found only in animal foods. Several studies have indicated that vegan children do not grow quite as tall as their omnivorous peers on average, and people eating a vegan diet are at a high risk of specific nutrient deficiencies including iron. Additionally, due to the diet’s extreme nature it is likely to be difficult to adhere to for long periods of time. We are skeptical that the diet recommended by The China Study optimizes this broader conception of health, although it could still be a good choice for people at high risk of cardiovascular disease. Criterion 3.3. Does the diet portion of the intervention promote an adequate nutrient intake for general health in the target audience? 1 out of 4 The diet received a score of 1, indicating that it is likely somewhat nutritionally inadequate. Fortunately The China Study recommends vitamin B12 supplementation, without which the diet would be very inadequate. With the addition of B12, the diet is mostly adequate but there is still an elevated risk of suboptimal nutrient intake, particularly of iron, long-chain omega-3 fatty acids, zinc, and iodine. Part of the problem is that certain nutrients, such as iron, are less efficiently absorbed from plant foods, so suboptimal absorption can occur even when dietary intake appears adequate. It may be possible to achieve nutrient adequacy on this diet, but it requires careful planning that is beyond the scope of the information in The China Study. Overall (average) score for healthfulness 2.3 out of 4

Most unusual claim

On page 17, The China Study claims that a low-fat, plant-based diet enhances athletic performance. This seems rather implausible. Professional athletes go to extreme lengths to achieve small performance gains, so if this diet yielded superior performance nearly all of them would be on it already. We performed a quick scientific literature search and did not identify compelling evidence to support this claim. One review paper considered eight primary studies and concluded that “consuming a predominantly vegetarian-based diet did not improve or hinder performance in athletes.” A second review paper suggests that vegan diets require “strategic management of food and appropriate supplementation… to achieve the dietary needs of most athletes satisfactorily.”

Other

The China Study spends a significant amount of time reporting and speculating about scientific misconduct and the influence of corporations in science. While some of these allegations have more than a grain of truth, the book frequently makes personal attacks against Campbell Sr.’s colleagues who do not hold his opinions. The book also ignores others in the nutritional sciences and public health communities who promote similar views. For example, the Harvard T.H. Chan School of Public Health has released a healthy eating plate as a counterpoint to the USDA’s MyPlate dietary guidance. The researchers behind the healthy eating plate state, “The Healthy Eating Plate is based exclusively on the best available science and was not subjected to political or commercial pressures from food industry lobbyists.” Notably, the Healthy Eating Plate recommends limiting dairy (it even excludes dairy as a visual cue compared to MyPlate), refined carbohydrates, and red and processed meat. It also suggests that protein intake should be primarily, but not exclusively, from plant sources. Additionally, it recommends a higher intake of vegetables than MyPlate. The China Study paints a selective picture of nutritional science and public health guidance in an apparent effort to discredit research that doesn’t align with its perspective.

Conclusion

The China Study is a scholarly and well-written book. It recommends reducing the intake of animal foods, processed foods, and refined grains, and composing the diet entirely of unrefined plant foods. Reducing intake of some of these foods, such as processed meat and refined grains, are likely to lead to overall improvements in health.

We evaluated three of the book’s key scientific claims and found that they were not very well supported overall. After consulting the original data and having it analyzed by a professional statistician, we conclude that a large study in China that The China Study is named after does not support the book’s claims. We did find the claim that a whole food plant-based diet reduces the risk of cardiovascular disease fairly convincing. The China Study generally cites references accurately and this is reflected in its high reference accuracy score. It received a middling score for healthfulness because although the diet will likely reduce the risk of obesity and some chronic diseases, it may also increase the risk of nutrient deficiencies unless carefully composed. The diet would be difficult to implement and maintain for most people due to its extreme nature, yet it may be worth considering for people at high risk of cardiovascular disease.

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