58 THE CHINA STUDY
The most significant finding of this experiment was this: foci devel-
oped only when the animals met or exceeded the amount of dietary
protein (12%) needed to satisfy their body growth rate.^39 That is, when
the animals met and surpassed their requirement for protein, disease
onset began.
This finding may have considerable relevance for humans even
though these were rat studies. I say this because the protein required
for growth in young rats and humans as well as the protein required to
maintain health for adult rats and humans is remarkably similar.4o,41
According to the recommended daily allowance (RDA) for protein
consumption, we humans should be getting about 10% of our energy
from protein. This is considerably more than the actual amount required.
But because requirements may vary from individual to individual, 10%
dietary protein is recommended to insure adequate intake for virtually
all people. What do most of us routinely consume? Remarkably, it is
considerably more than the recommended 10%, The average American
consumes 15-16% protein. Does this place us at risk for getting cancer?
These animal studies hint that it does.
Ten percent dietary protein is equivalent to eating about 50-60 grams
of protein per day; depending on body weight and total calorie intake. The
national average of 15-16% is about 70-100 grams of protein per day; with
men at the upper part of the range and women at the lower end, In food
terms, there are about twelve grams of protein in 100 calories of spinach
(fifteen ounces) and five grams of protein in 100 calories of raw chick peas
Gust over two tablespoons). There are about thirteen grams of protein in
100 calories of porterhouse steak Gust over one and a half ounces).
Yet another question was whether protein intake could modify the
all-important relationship between aflatoxin dose and foci formation.
A chemical is usually not considered a carcinogen unless higher doses
yield higher incidences of cancer. For example, as the aflatoxin dose
becomes greater, foci and tumor growth should be correspondingly
greater. If an increasing response is not observed for a suspect chemical
carcinogen, serious doubt arises whether it really is carcinogenic.
To investigate this dose-response question, ten groups of rats were
administered increasing doses of aflatoxin, then fed either regular levels
(20%) or low levels (5-10%) of protein during the promotion period
(Chart 3.7^34 ).
In the animals fed the 20% level of protein, foci increased in number and
size, as expected, as the aflatoxin dose was increased. The dose-response