The China Study: What Did It Really Find?

What Did The China Study Really Study?

One of the most frequent questions I get as a nutrition consultant is, “What do you think of The China Study?”  For those of you unfamiliar with it, this is a book written by T. Colin Campbell, PhD in 2006 which encourages a vegan diet (no animal sourced food) and inspired the recent documentary Forks Over Knives.  The premise of the book and the movie is that all animal foods are dangerous and are the underlying cause of today’s leading killers - heart disease and cancer.  It is further claimed that these can be prevented or even cured by avoiding all animal products and eating a diet consisting of only whole, unprocessed plant foods.

The China Study quickly became the “Bible” of the vegan and vegetarian communities.  It was the undisputed proof that meat was bad and plant-only was good.  While the book contains many well-referenced arguments, upon closer inspection it becomes clear that many of the claims result from selecting and manipulating the data that fits the hypothesis, rather than an unbiased analysis of all the information collected. 

Does Animal Protein Cause Cancer?  If Not, What Does?

Campbell’s main claim is that animal protein causes cancer.  Here’s how he arrived at that conclusion.  While working in the Philippines on a project to help combat malnutrition a colleague informed him of a startling observation.  It was discovered that wealthy Filipinos were suffering from liver cancer at a much higher rate than their less-affluent counterparts.  Disregarding a substantial number of lifestyle differences, Campbell believed the higher cancer rates were linked to their higher intake of animal protein.  To further support his view he also learned of a recent study from India showing that a high protein intake encouraged liver cancer in rats, while a low protein intake seemed to prevent it.  This led Campbell to investigate the relationship of nutrition (specifically protein ingestion) with cancer growth.

The China Study is based on Campbell’s experiments.  His basic methodology was to expose rats to very high levels of aflatoxin—a known carcinogen (cancer causer) produced by mold that grows on peanuts and corn.  He then fed them a diet consisting of varying levels of the milk protein casein. In study after study Campbell found that rats consuming 5 percent of their calories as casein had no tumors, while rats eating 20 percent of their calories as casein developed abnormal growths indicating the beginning of liver cancer. 

Not to be “biased” he repeated the same tests with wheat protein and soy protein which showed no cancer growth.  He did not test any other animal based protein.  His conclusion from these experiments was that all animal protein—but not plant protein—could promote cancer growth.  But the question remains.  Can the effects of this isolated casein, which does not appear this way in nature (by this I mean how we actually eat food) be generalized to all forms of milk protein?  And if so, can this then be attributed to all forms of animal protein?  It seems like quite a stretch particularly when there are many studies that show the other major milk protein, whey, actually suppresses tumor growth.

On a side note - one the experiments he did not report in the book showed that when wheat gluten was supplemented with the amino acid lysine to create a complete protein, it behaves exactly like casein to promote tumor growth.  This means that it is not necessarily the animal protein, but rather the full spectrum of amino acids in a complete protein that provide the right building blocks for growth, whether it be of malignant cells or healthy ones.

Thus, one could argue that a meal of rice and beans which creates a complete protein would provide the same cancer-promoting amino acids that animal protein does. One could further argue that Campbell’s experiments lose their relevance when placed in the real world in contrast to the scientifically manipulated menu of casein, sugar, and corn oil fed to the rats (poor rats!!).

However, there is even more to the story – again what the actual research showed and was not reported by Campbell.  Are you ready? Yes the rats consuming the high-casein diet were getting the liver cancer as described.  Yet the ones in the low-casein groups were suffering an even worse fate. Basically, they were dying before they could get the liver cancer.  The acute toxicity of aflatoxin was poisoning the rats resulting in cell genocide and premature death. As I like to say it is not what happens in the test tube, but what happens in the body.  Here’s what happens in the body. The lack of protein creates a deficiency that inhibits the liver’s ability to detoxify the body.  Less of the aflatoxin gets converted into cancer-causing metabolites, but instead causes massive (and eventually deadly) tissue damage.  The India research showed the same results.

There was another Indian study (again not reported by Campbell) that exposed monkeys to the aflatoxin with the same protein parameters, but with one important difference.  These monkeys were exposed to lower, daily doses of aflatoxin, more like they would experience in the real world where aflatoxin is consumed frequently in small amounts from contaminated foods. Guess who got the cancer here?  You guessed it – the low protein monkeys!

It appears that the cancer growth is related more to the aflatoxin exposure.  When the exposure is unrealistically high the animals eating a low-protein diet don’t get cancer because their cells are too busy dying, while animals eating a higher protein diet are still consuming enough dietary building blocks for the growth of cells—whether healthy or cancerous to keep them alive. With a more moderate dose of aflatoxin, animals eating a low-protein diet develop cancer while their higher-protein counterparts remain in mighty fine health.
So, here is what is actually true:
1. High-quality protein promotes cell growth no matter where it comes from;
2. Protein deficiency inhibits the liver’s ability to detoxify dangerous substances; and
3. With more realistic doses of aflatoxin, protein is actually tremendously protective against cancer, while protein-restricted diets prove harmful.

What was the actual China Study?

Also known as the China-Cornell- Oxford Project, the China Study was an enormous undertaking exploring diet and disease patterns in rural China.  It collected data on 367 variables and generated over 8,000 statistically significant correlations between nutrition, lifestyle factors and a variety of diseases.  Obviously there was a lot to choose from!

Here we ask the fundamental question.  Are correlation and causation always the same?  The answer – when it is in your best interests to prove a point they are!  Campbell stated that, “People who ate the most animal-based foods got the most chronic disease,” and “People who ate the most plant-based foods were the healthiest and tended to avoid chronic disease.”  

Campbell discusses how the data showed relationships between cholesterol and cancers, as well as cholesterol and animal protein intake, jumping to the conclusion that animal protein and those same cancers must be linked.  Yet nowhere in the data is that shown.  The original China Study data shows virtually no statistically significant correlation between any type of cancer and animal protein intake.
What was found is that wheat consumption (and not rice) was strongly associated with higher insulin levels, higher triglycerides, coronary heart disease, stroke and hypertensive heart disease within the China Study data—far more so than any other food, including protein of any type. 

So what did the actual data from the original publication show?   Sugar, soluble carbohydrates, and fiber all have correlations with cancer mortality about seven times the magnitude of that of animal protein, and total fat and fat as a percentage of calories were both negatively correlated with cancer mortality. 

There is also the issue of balance in reporting the “facts.”  Throughout The China Study Campbell will present a study showing a relationship with animal protein and a specific disease (to support his hypothesis) and at the same time ignore other studies showing the same relationship with plant protein (which does not support his view).   For example, he discusses the role of cow’s milk in causing autoimmune diseases, but ignores the role of wheat gluten in causing autoimmune diseases.

In Conclusion It’s All About Balance

To me, in the end it is all about presenting a balanced picture.  You can find all kinds of studies to support all kinds of theories about nutrition.   I believe that a vegan or vegetarian or plant based diet can be very good for someone for a particular period of time.  It can be healing.  But what is it being compared to?  What did they eat before?  Is the diet in and of itself healthy and providing all the nutrients or is it just cleaning up what was there?  Will this same diet provide long term health?  What is the significance of the age the diet is started?  In looking at animal product, what is the source?  It is a healthy animal raised in a healthy manner?  Or, is it a factory farmed animal raised in confinement on hormones, antibiotics, and food that it would not eat in nature?  All of this makes a huge difference.

Thanks to the Weston A. Price Foundation as a resource for this article.
