The China Study–why we should eat less animal protein
I recently finished reading The China Study. I got this book thinking it would be about the China study, where the health and diets of over 6000 rural Chinese were examined. It ended up being more of a summary about the life work of researcher T. Colin Cambell, Ph.D. I think a better title for the book would have been The Danger of Animal Protein.
Cambell starts off sharing some depressing statistics about America’s health. This really shouldn’t be new to any of us–we’re fat, our hearts are failing, our bodies are riddled with cancerous tumors, diabetes is more and more common, and our main solution to these problems are more and more pills, with an expensive surgical procedure or two added in for good measure. In fact, he says that half of Americans have a health problem that requires taking a prescription drug every week. I’m sure the drug companies like that.
What they probably don’t like, and don’t want you to know, is that diet can be just as powerful as medication when it comes to our health. In fact, Cambell claims that the most recent scientific research shows that dietary changes can enable diabetics to go off their medication, heart disease can be reversed through diet alone, and breast cancer is related to the levels of female hormones in the blood (which are determined by the foods we eat).
Cambell grew up in the Midwest on a farm, eating lots of meat and dairy. His Ph.D. research at Cornell was involved with finding ways to make cows and sheep grow faster. Later, he worked in the Philippines with malnourished children, trying to get these poor, 3rd world children access to high quality protein, like us fortunate Westerners have. He was startled to find though that the children eating the most protein, those from wealthier families, were actually more likely to get liver cancer, which had an unusually high prevalence in the Philippines.
Around that time, Cambell stumbled across a study that found that animal protein might be to blame. Rats were fed either a diet comprised of 20% animal protein or 5%. Then they were given a potent carcinogen called aflatoxin (a fungus found on moldy peanuts). The animals with the low protein diet never developed cancer. Not a single one. However, 100% of the animals on the higher protein diet got liver cancer. In America, we tend to eat 14-18% of our calories in the form of protein, 70-80% of which comes from animal sources. Are you scared yet?
No one wants to hear that protein might be the cause of Western diseases. We’ve already blamed fat for several decades, and Americans seemed to accept low-fat alternatives. Then most recently, we blamed carbs, and people quickly gave up bread and pasta for bacon and eggs. But protein? Who wants to give that up? Especially when the form of protein used in this study was casein, which comprises 87% of cow’s milk protein. Was Cambell implying that the healthiest diet was a vegan one?! We are so used to the notion that protein is healthy. Eating a lot of animal products is a sign of status. We can afford to eat this way so why shouldn’t we?!
Cambell knew that no one would buy that protein was problematic, so he carefully conducted his own studies. He was shocked to get similar results. He found that “dietary protein proved to be so powerful in its effect that we could turn on and off cancer growth simply by changing the level consumed.” Most importantly, the level of protein examined was well within the range of what Americans consumed. Once Cambell had collected enough animal data, he took his theories into a clinical setting and set out to conduct The China Study.
While Americans eat 15+% of our calories in the form of protein (70-80% of which comes from animal sources), only 9-10% of the rural Chinese diet is protein (with a mere 10% of that protein coming from animal sources). The China Study showed that rural Chinese eat very little animal protein. Interestingly enough, they also ate more calories than Americans (2641 vs. 1989) although they weighed less. Even the least active Chinese ate more calories and weighed less than Americans. Fiber intake was about three times higher in rural China than America, while total fat intake was less than half what we typically eat. Again, most notable, was that animal protein made up only 0.8% of the rural Chinese diet, compared to 10-11% in the U.S.
So what did these changes in diet mean for health? Were the rural Chinese healthier than us? The average blood cholesterol in the study was 127 mg/dL, almost 100 points less than the average of 215 mg/dL in the U.S. (interestingly, when I had my cholesterol measured a few months ago, they wouldn’t report anything below 150. The lowest lows here are actually quite high for the rural Chinese!) As blood cholesterol decreased, so did many diseases, including cancers of the liver, rectum, colon, lung, breast, brain, stomach, and esophagus. And cancer rates weren’t the only difference. In America, the rate of coronary heart disease is seventeen times higher among American men than rural Chinese men. Seventeen!
Cambell presents much more information about The China Study and what he found. He then devotes the entire middle section of his book to discussing studies that link animal protein to heart disease, obesity, diabetes, cancer, and autoimmune diseases. The research is very impressive.
And that’s where the animal protein bashing ceases. Up until this point, I thought Cambell had convincingly formed a very strong theory–that animal protein may be the cause of many Western diseases. He had animal data and human data. He had correlational studies and clinical studies. But he failed to test his final theory! I would have loved to have seen him take a large group of Americans with all the hosts of health problems we face and put them on a low animal protein diet and see specifically what happens. I would have liked to see this vegan diet’s effects in our population, not just in the rural Chinese. The gold standard in science is the controlled, double-blind study, not the correlational one he conducted in China. I want to see two groups of Americans eat an identical diet, but one is filled with vegetable protein while the other animal protein, and see the results. Because we all know that there are plenty of meat-eating cultures that our healthier than ours. And humans have been eating animal products for thousands of years without the exceptionally high rates of heart disease and cancer we have now. He didn’t have an explanation for any of this.
I also found myself thinking about all the vegetarians and vegans I know. Are they healthier than my meat-eating friends? Not really. It wasn’t until Appendix B that I reached a possible explanation for this–a graph shows what a typical American vegetarian diet looks like and it’s still high in animal protein (most likely from dairy and eggs). In fact, American vegetarians get 40-60% of their calories from animal products, while non-vegetarians eat 60-70%. That’s not really much of a difference.
Cambell repeatedly said that vegetable protein was not implicated in the disease process like animal protein was. So presumably, we can eat all the nuts and soy we want. But Cambell never touched on some of the controversies with soy, especially in the way Americans consume it (historically, soy has almost always been fermented before consumption, but the majority of soy products eaten by Americans are not). I tried eating mostly vegan while reading this book and I was ravenous all the time. I believe in the importance of consuming protein or fat with your carbohydrates, in order to slow their digestion and absorption into the blood stream. When I eat protein and fat at most meals and snacks, my blood sugar seems more stable and I don’t experience spikes and drops. But without animal sources of protein and fat, I was left with mostly avocados, nuts, and seeds. And despite eating them by the handful, I was still hungry! It would have been helpful if he had some menu suggestions or recipes, but his guidelines were minimal.
Other questions plague my mind–what about organic animal protein? Or pastured animal protein? Is one type of animal protein more dangerous than others? Is protein the sole problem, or could it also be pesticides, growth hormones, and antibiotics in animal products? What about fish? Cambell says to limit your intake of fish, but I don’t recall a single study mentioned in this book that specifically examined seafood protein. Is that safe to consume?
Cambell repeatedly emphasizes the importance of a whole food, plant based diet. But I think that most readers are left thinking that only animal protein is to blame. And I worry that if most Americans cut out animal products, they’ll be left eating mostly refined carbohydrates, which are also not healthy. I wish he had discussed replacing animal products with plant products, instead of just eliminating animal products. He never once mentioned specifically what the rural Chinese ate in his China Study. I think it would have been prudent to mention all the produce they likely eat and all the breads and refined carbs they probably don’t.
The final section of the book sheds light on what he calls “the dark side” of science. The corruption in industry and government is becoming more and more obvious to me, but to hear his stories of doctors being essentially kicked out of their hospitals for offering dietary solutions to heart disease patients was disturbing to say the least. What if the doctors we trust to keep us healthy are making decisions based on money over health? After all, Campbell points out that heart surgery funded most of the hospital’s expenses in his two examples. Hospitals don’t make a penny when your heart clears up because you changed your diet.
And that brings me to the final point of this book. Why isn’t nutrition more important to the research community? Why does no one want to hear about how dietary changes can help prevent and treat and even sometimes reverse disease? Because no one profits from nutrition advise. If we can find a magical nutrient and turn it into a supplement, then we’re interested in nutrition. But if the research suggests that carrots can lower lung cancer, but not isolated vitamin A (which actually raised rates of lung cancer), then forget it. You can’t patent a carrot. We’d much rather take a pill or have surgery to treat disease, even with all the associated risks. Medication error and adverse events from drugs or surgery (such as hospital borne infections, which killed the OB GYN that delivered my sister just months after he retired) kill 225,400 people per year in the U.S., making our health care system the 3rd leading cause of death, following cancer and heart disease. We’d rather spend more money and take more risks in our health care system than change our lifestyle. What are the risks associated with diet modification? And costs? Nothing compared to medications and surgeries. Why aren’t more doctors giving us sound nutritional advice? Why don’t doctors get nutritional training in medical school, at least some that isn’t funded by the dairy industry? Why was no one suspicious that something was awry when the U.S. Food and Nutrition Board (FNB) recommended in 2002 that added sugars comprise no more than 25% of total calories consumed when the World Health Organization (WHO) says the upper safety limit is 10%? Why does the WHO rank the U.S. as 37th best in the world according to health care performance, even though we spend the most money?
If it’s really as simple as changing our diet, then more people need to know this. The China Study hasn’t completely convinced me to foresake all animal protein, but I am intrigued and am already limiting it more than I did previously. There certainly is enough research presented in this book to make me question the safety of my diet.