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The China Study 2 – Rats

Posted by tinako on November 21, 2009

This is a continuation of my quest to explain why I criticize the nutrition advice given by Jean Carper and the American Cancer Society, among others.  Hopefully you found the rat experiment described in my last post to be interesting.  (By the way, I want to express my deep compassion and sorrow for all the animals used in these experiments.  This isn’t something I condone.)

Dr. Campbell gives a nice analogy in his book between cancer and growing a lawn [p.48].  He says that cancer has three stages: initiation, which is like the seeding of a lawn, only the seeds are carcinogens; promotion, which is like the grass beginning to grow; and progression, which is when the lawn takes over wildly and spreads onto the driveway and into the gardens.

Initiation can take place in a matter of minutes: you are exposed to the carcinogen and almost instantly it can be seeded in your tissues.  These carcinogens “mutate normal cells into cancer-prone cells.”     This is a permanent alteration involving damage to the DNA, and all daughter cells will be cancerous.  Initiation is irreversible.

But like grass seeds which need water, sunlight, and nutrients, the cancer-prone cells need certain conditions met.  If that doesn’t happen, the cancer cells will remain dormant indefinitely.  If they begin to grow and then these favorable conditions are stopped, cancer growth stops as well.  “Promotion is reversible, depending on whether the early cancer growth is given  the right conditions in which to grow” [p.50].  Some dietary factors, called promoters, feed cancer growth, and anti-promoters slow cancer growth.  Wouldn’t you like to know what these are?

Dr. Campbell set out to answer some questions based on the rat study: He wanted to confirm that a low-protein diet suppresses tumor formation and find out why.  He talks in great detail about what they discovered about the “why,” but I am going to mostly follow the rats.

One thing that helped him was that it had just been discovered that tiny clusters of cells called “foci” are precursors and predictive of tumor development.  They were therefore able to study protein’s effect on foci and avoid spending a lifetime and millions of dollars waiting for rats to grow cancer cells. First they replicated the earlier rat experiment and found that foci grew far less on a 5% protein diet (there’s a chart, and it looks like about 0.8 foci response) vs. a 20% diet (3.0 foci response).  Next they exposed the animals to different amounts of aflatoxin.  They gave group A a high dose of aflatoxin and a 5% protein diet, and group B a low dose of aflatoxin and a 20% protein diet.  The remarkable results were group A had about an 8 foci response, group B, 90.  “Foci development, initially determined by the amount of carcinogen exposure, is actually controlled far more by dietary protein consumed during promotion” [p.56].

With this information they refined their experiments.  Now they dosed all the animals with the same amount of carcinogen, then fed either 5% or 20% protein during a 12-week promotion stage divided into four three-week periods.  When animals were fed 20% protein during periods 1 and 2, their foci continued to develop, but when these animals were switched to a 5% diet for period 3 there was a sharp decrease in foci development.  When they were switched to a 20% diet for period 4, what do you think?  Foci development was turned on once again.

In another experiment, animals were fed 20% protein in period 1, then 5% in period 2, and foci development decreased sharply.  They were returned to 20% protein for period 3 and foci development again increased.  These experiments showed that foci growth at all stages of development could be switched up and down by altering the amount of protein consumed.  It also showed that the cancer did not go away, but just lay dormant, even for many weeks.

In their next experiment, they wanted to find out what was the magic number between 5% and 20% protein.  Using rats, they discovered that foci did not develop up to about 10% protein, and these results were repeated by a Japanese professor.  10% protein is about the dietary protein need of rats, and they began to see that the problem was in consuming more than we need.  The protein needs of rats and humans is very similar.  The RDA is 10%, which is more than the actual amount needed, in order to be sure people with varying needs get enough.  The average American consumes 15-16%.  The average for nurses in that famous Nurse’s study is 19%!

They continued with their experiments on rats.  A chemical is considered a carcinogen if higher doses yield more cancer.  So they gave varying amounts of aflatoxin to ten groups of rats and then fed half of each group either a 5-10% or 20% protein.  There is a remarkable chart here that shows the 5% protein rats as a straight horizontal line, all data points for increasing aflatoxin doses just over zero.  The 20% rats start a little above the 5% rats and then start going way up as aflatoxin dose increases.  There was no dose-response curve for the 5% rats.  There was no foci response, even when the rats were given the maximum tolerated aflatoxin dose (I took this to mean that any more injected into them killed them outright, not of cancer but perhaps of a huge injection).

Next they wondered whether different types of protein would yield different results.  For all the experiments, they were using the animal protein casein, which makes up 87% of cow’s milk’s protein [p.59].  So they tried the same experiments with plant protein (they tried both gluten and soy separately).  In their experiments, plant protein did not promote cancer growth, even at the 20% levels.  On the chart, 20% casein is at about 80 foci response and 20% gluten is just above 5% casein, both appearing to be under 10 foci response.

With these preliminary experiments done, they were ready for the big one which would follow several hundred rats for their lifetimes.  Are you ready?  Rats live about two years, so the study was 100 weeks.  “All animals that were administered aflatoxin and fed the 20% casein were dead or near death from liver tumors at 100 weeks.  All animals administered the same level of aflatoxin but fed the 5% protein diet were alive, active,… with sleek coats at 100 weeks.  This was a virtual 100 to 0 score, something almost never seen in research” [p.61].

In the same experiment they “switched the diets of some of the rats at either 40 or 60 weeks, again to investigate the reversibility of cancer promotion.  Animals switched from a high-protein diet to a low-protein diet had significantly less tumor growth (35-45% less) than animals fed a high protein diet.  Animals switched from a low-protein diet to a high-protein diet halfway through their lifetimes started growing tumors again…  Nutritional manipulation can turn cancer ‘on’ and ‘off.’ ”  In case you’re skeptical about the experiments that relied on foci, they also examined foci this time and reconfirmed the very close relationship between foci and tumors.

The conclusion is inescapable.  Cow’s milk protein, at levels commonly ingested by humans, is an incredibly potent cancer promoter in rats dosed with aflatoxin.   Next Dr. Campbell set out to investigate other species, other organs, other carcinogens.


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