Forks Over Knives, or Hype Over Facts?

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forks over knivesFact-checking a flawed documentary

An important documentary came out last summer. Roger Ebert raves about it. George Strombolopolous ranks it the number one movie of 2011.

It’s a film about food and health.

Arguing that some of our most devastating illnesses – heart disease, stroke, type 2 diabetes and cancer, among others – may be avoidable, “Forks Over Knives” makes a strong case that meat, fat, eggs, sugar and milk are a major part of the problem. And for the most part, the case is compelling.

The film takes us into the lives of patients with type 2 diabetes and heart disease. We learn how their health was dramatically improved when they adopted a low fat, whole foods, plant-based diet – a diet high in fruits, vegetables, grains and seeds – but with no meat, processed foods, dairy, eggs or oil. We follow some of the patients and watch their cholesterol, blood pressure and cardiovascular inflammation drop.

“Forks Over Knives” tells us also how collusion between big agribusiness and the FDA has put unhealthy foods on the plates of American schoolchildren, how it has corrupted the Food Pyramid we are all familiar with. We’re told a bit about the environmental damage, too, and the suffering inherent in animal agriculture.

But mostly we learn about the research of several physicians and scientists, notably Drs. Caldwell Esselstyn and Colin Campbell.

Esselstyn, at the Cleveland Clinic, prescribes a low fat, whole foods, plant-based diet to patients with serious heart disease. In a study published in the Journal of Family Practice, he reports that the diet halted the advancement of the disease in 11 of 18 patients; four even showed evidence of disease regression. Clearly cardiac patients would be hard-pressed to do better than follow Esselstyn’s advice.

Colin Campbell’s work is more fundamental. A nutritional biochemist at Cornell, he is most famous as leader of the 20 year China-Cornell-Oxford study. Tracking diet, lifestyle and disease in 6500 people across 65 rural Chinese counties, some 8000 correlations between diet and disease were found. While the interpretation of much of the data is contentious, the study indisputably showed that diseases like heart disease, diabetes and cancer are rarer in regions of China where consumption of animal products is low than in regions where it is high. Without a doubt, eating low on the food chain is good for our health.

For all of the good information in “Forks Over Knives,” there are some serious problems.

Like many advocacy films, “Forks Over Knives” sometimes exaggerates its claims. The interpretations of the scientific and clinical data are often open to question and are sometimes, to a scientifically trained viewer, clearly in error. Most of the errors are minor, but some have serious implications. One wonders where the fact-checkers were.

One example is the claim that animal proteins cause cancer.

A substantial amount of time in the film is spent on this issue, despite the fact that a quick read of the original papers reveals a fatal flaw in the thesis. The problem is that something else the experimenters included was causing the cancer.

Yes, unfortunate rats were fed diets containing either high (20% of calories) or low (5% of calories) amounts of the milk protein casein and, yes, there were differences in the number of cancerous lesions they developed. But, very significantly, the rats were also given daily doses of aflatoxin, one of the most potent carcinogens known – and a compound with severe immediate effects as well.

No matter how one looks at it, ignoring even interspecies differences (and ethical concerns), one cannot demonstrate that a protein causes cancer in animals who are being concurrently dosed with a major carcinogen.

In fact, the people who did the original work knew this. They were not attempting to test whether casein was a carcinogen, but were interested, rather, in the possibility that variations in dietary protein might protect against aflatoxin’s short-term effects.

Besides being a major carcinogen, aflatoxin can very quickly cause necrosis of the liver, i.e., it kills liver cells. What the scientists found was that the high protein diet was protective; it prevented this damage to the liver. All 30 of the aflatoxin-dosed rats fed the high casein diet survived the full year of the study; in contrast, of the 30 rats on the low protein diet, 18 died. The dead exhibited the signs of severe liver damage typical of aflatoxin poisoning. Thus, the most likely explanation for the higher levels of cancer in the rats eating the high casein diet is that the protein somehow kept the liver cells alive long enough to succumb to the carcinogenic effect of that daily dose of aflatoxin. That those on the low protein diet developed fewer cancers may well indicate that their liver cells were too sick even to divide, a prerequisite for becoming cancerous.

All of this may seem academic. But credibility matters when we’re trying to convince others to change their diets. It is far better to report accurate information than to mislead people with interpretations that are highly unlikely to be correct. While red and processed meats are indeed associated with increased cancer, it is far more likely that this is due to additives in the meat (put there intentionally or through the environment) than it is to any carcinogenic activity of meat protein itself.

The second example of an exceptionally poorly substantiated claim in “Forks Over Knives” is potentially more serious. Taken to heart by seriously ill people, it could cost lives.
While the film doesn’t explicitly state it, the implication is made that breast cancer, once diagnosed, might be cured by the adoption of a plant-based diet. The claim is based on the case of a single person who, after a double mastectomy, adopted a whole foods, plant-based diet along with a strenuous exercise regime and has remained healthy ever since. The probability that such a regimen will cure the vast majority of diagnosed breast cancers is near zero. Cancers involve changes in the genetic makeup of cells, such that the cells no longer respond to signals to stop growing. For the vast majority of cancers, dietary changes will not somehow make them responsive to those signals again.

It is understandable that persons who have made changes to their diets and obtained spontaneous (or otherwise) remissions often credit the changes they made with “curing” their disease. An Internet search turns up highly disparate dietary choices people with cancer have made – ranging from raw vegan to high meat “paleo” diets – all of which the individuals claim saved their lives. The point to remember is that we don’t hear from those who made similar choices and died.

That said, if you are ill with cancer, it is probably good for you to adopt a whole foods, plant-based diet. But don’t forgo conventional treatment. Low fat, whole food, plant-based diets do reverse type 2 diabetes in many people; and they alleviate and sometimes reverse heart disease as well. There is strong scientific evidence for this, especially diabetes. But cancers are very different. Relying on diet alone after diagnosis is very probably a very bad idea.

For the rest of us, the best approach is to adopt a whole foods, plant-based diet now, before we develop any of these diseases. By adopting such a diet, one is substantially reducing the chances of developing the diseases at all.

And of course, health is not the only reason to leave animal products behind. Widespread adoption of plant–based diets would substantially slow global warming. It would reduce nitrogen and phosphorus runoffs that are causing dead zones at the mouths of our rivers and prevent the overfishing-driven collapse of ocean ecosystems. We’d be able to feed many more people off of a lot less land. And we’d spare literally tens of billions of animals each and every year from lives of hellish torture. It’s a slam dunk case, really. And, as a bonus, on average, personal health would be substantially improved.

So pay attention to the message of “Forks Over Knives.” It’s important stuff. Just be careful about accepting at face value every claim they make.


Dave SteelewebDavid Steele is a molecular biologist and President of Earthsave Canada. His piece was originally published in Canada EarthSaver.



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