The China Study (9 page)

TH E CH I NA STU DY
48
hindsight, we must have succeeded. The NIH funding for this study con-
tinued for the next nineteen years and led to additional funding from
other research agencies (American Cancer Society, the American Institute
for Cancer Research and the Cancer Research Foundation of America).
On these experimental animal findings alone, this project gave rise to
more than 100 scientific papers published in some of the best journals,
many public presentations and several invitations to participate on expert
panels.
ANIMAL RIGHTS
The rest of this chapter concerns experimental animal research, all
of which included rodents (rats and mice). I know well that many
oppose the use of experimental animals in research. I respect this
concern. I respectfully suggest, however, that you consider this:
very likely, I would not be advocating a plant-based diet today if
it were not for these animal experiments. The findings and the
principles derived from these animal studies greatly contributed
to my interpretations of my later work, including the China Study,
as you will come to see.
One obvious question regarding this issue is whether there
was an alternative way to get the same information without us-
i n g experimental animals. To date, I have found none, even after
seeking advice from my "animal rights" colleagues. These experi-
m e n t a l animal studies elaborated some very important principles
of cancer causation not obtainable in human-based studies. These
principles now have enormous potential to benefit all of our fel-
low creatures, our environment and ourselves.
THREE STAGES OF CANCER
Cancer proceeds through three stages: initiation, promotion and progres-
sion. To use a rough analogy, the cancer process is similar to planting a
lawn. Initiation is when you put the seeds in the soil, promotion is when
the grass starts to grow and progression is when the grass gets completely
out of control, invading the driveway, the shrubbery and the sidewalk.
So what is the process that successfully "implants" the grass seed in
the soil in the first place, i.e., initiates cancer-prone cells? Chemicals
that do this are called carcinogens. These chemicals are most often

49
TURNING OFF CANCER
CHART 3.1: TUMOR INITIATION BY AFLATOXIN INSIDE A LIVER CELL
(2) AF is metabolized
by an enzyme.
0~@t'YIDJ
j
(3) A dangerous
~ A~
_p_rod_u_ct_(_A_F_*_)-'                                          Cancerous
~---v
is formed.
OJ"''
'-
(4) It attacks the
cell's DNA.
(5) Most damaged
(6) A cell multiplies
DNA is repaired,
before the damaged
but sometimes ...
DNA is repaired and
Cancer Initiation
permanently damaged,
cancerous celis arise
After entering our cells (Step 1), most carcinogens do not, themselves, initiate the cancer
process. They first must be converted to products that are more reactive (Steps 2 & 3), with
the help of critically important enzymes. These carcinogen products then bind tightly to
the cell's DNA to form carcinogen-DNA complexes, or adducts (Step 4).
Unless repaired or removed, carcinogen-DNA adducts have the potential to create chaos
with the genetic workings of the cell. But nature is smart. These adducts can be repaired,
and most adducts are repaired fairly quickly (Step 5). However, if they remain in place
while cells are dividing to form new "daughter" cells, genetic damage occurs and this new
genetic defect (or mutation) is passed on to all new cells formed thereafter (Step 6). 17
the byproducts of industrial processes, although small amounts may
be formed in nature, as is the case with aflatoxin. These carcinogens
genetically transform, or mutate, normal cells into cancer-prone cells.
A mutation involves permanent alteration of the genes of the cell, with
damage to its DNA.
The entire initiation stage (Chart 3.1) can take place in a very short
period of time, even minutes. It is the time required for the chemical
carcinogen to be consumed, absorbed into the blood, transported into
cells, changed into its active product, bonded to DNA and passed on to
the daughter cells. When the new daughter cells are formed, the process
is complete. These daughter cells and all their progeny will forever be
genetically damaged, giving rise to the potential for cancer. Except in rare
instances, completion of the initiation phase is considered irreversible.

THE CHINA STUDY
50
At this point in our lawn analogy, the grass seeds have been put in
the soil and are ready to germinate. Initiation is complete. The second
growth stage is called promotion. Like seeds ready to sprout blades of
grass and turn into a green lawn, our newly formed cancer-prone cells
are ready to grow and multiply until they become a visibly detectable
cancer. This stage occurs over a far longer period of time than initiation,
often many years for humans. It is when the newly initiated cluster mul-
tiplies and grows into larger and larger masses and a clinically visible
tumor is formed.
But just like seeds in the soil, the initial cancer cells will not grow and
multiply unless the right conditions are met. The seeds in the soil, for
example, need a healthy amount of water, sunlight and other nutrients
before they make a full lawn. If any of these factors are denied or are
missing, the seeds will not grow. If any of these factors are missing after
growth starts, the new seedlings will become dormant, while awaiting
further supply of the missing factors. This is one of the most profound
features of promotion. Promotion is reversible, depending on whether the
early cancer growth is given the right conditions in which to grow. This is
where certain dietary factors become so important. These dietary fac-
tors, called promoters, feed cancer growth. Other dietary factors, called
anti-promoters, slow cancer growth. Cancer growth flourishes when
there are more promoters than anti-promoters; when anti-promoters
prevail cancer growth slows or stops. It is a push-pull process. The pro-
found importance of this reversibility cannot be overemphasized.
The third phase, progression, begins when a bunch of advanced cancer
cells progress in their growth until they have done their final damage. It
is like the fully-grown lawn invading everything around it: the garden,
driveway and sidewalk. Similarly, a developing cancer tumor may wander
away from its initial site in the body and invade neighboring or distant
tissues. When the cancer takes on these deadly properties, it is considered
malignant. When it actually breaks away from its initial home and wan-
ders, it is metastasizing. This final stage of cancer results in death.
At the start of our research, the stages of cancer formation were
known only in vague outline. But we knew enough about these stages
of cancer to be able to structure our research more intelligently. We had
no shortage of questions. Could we confirm the findings from India that
a low-protein diet represses tumor formation? More importantly, why
does protein affect the cancer process? What are the mechanisms; that
is, how does protein work? With plenty of questions to be answered, we

TURNING OFF CANCER                                    51
went about our experimental studies meticulously and in depth in order
to obtain results that would withstand the harshest of scrutiny.
PROTEIN AND INITIATION
How does protein intake affect cancer initiation? Our first test was to
see whether protein intake affected the enzyme principally responsible
for aflatoxin metabolism, the mixed function oxidase (MFa). This en-
zyme is very complex because it also metabolizes pharmaceuticals and
other chemicals, friend or foe to the body. Paradoxically, this enzyme
both detoxifies and activates aflatoxin. It is an extraordinary transfor-
m a t i o n substance.
THE ENZYME uFACTORY"
(1) Aflatoxin (AF)
enters the cell.
(2) AF is metabolized
by an enzyme.
In a simplistic way, the MFO enzyme system can be thought of as a factory
within the industrious workings of the cell. Various chemical "raw materi-
als" are fed into the factory, where all the complex reactions are performed.
The raw materials may be disassembled or assembled. After a transforming
process, the "raw material" chemicals are ready to be shipped out of the
factory as mostly normal, safe products. But there also may be byproducts
of these complex processes that are exceptionally dangerous. Think of the
smokestack at a real-life factory. If someone told you to stick your face down
a smokestack and breathe deeply for a couple hours, you'd refuse. Within
the cell, the dangerous byproducts, if not held in check, are the highly reac-
tive aflatoxin metabolites that go on to attack the cell's DNA and damage its
genetic blueprint.

52                             THE CHINA STUDY
At the time we started our research, we hypothesized that the protein
we consume alters tumor growth by changing how aflatoxin is detoxi-
fied by the enzymes present in the liver.
We initially determined whether the amount of protein that we eat
could change this enzyme activity. After a series of experiments (Chart
3.2 18 ) , the answer was clear. Enzyme activity could be easily modified
simply by changing the level of protein intake.1s-21
Decreasing protein intake like that done in the original research in
India (20% to 5%) not only greatly decreased enzyme activity, but did
so very qUickly. 22 What does this mean? Decreasing enzyme activity via
low-protein diets implied that less aflatoxin was being transformed into
the dangerous aflatoxin metabolite that had the potential to bind and to
mutate the DNA.
We decided to test this implication: did a low-protein diet actually
decrease the binding of aflatoxin product to DNA, resulting in fewer
adducts? An undergraduate student in my lab, Rachel Preston, did the
experiment (Chart 3.3) and showed that the lower the protein intake,
the lower the amount of aflatoxin-DNA adducts.23
We now had impressive evidence that low protein intake could mark-
edly decrease enzyme activity and prevent dangerous carcinogen bind-
i n g to DNA. These were very impressive findings, to be sure. It might
even be enough information to "explain" how consuming less protein
leads to less cancer. But we wanted to know more and be doubly assured
of this effect, so we continued to look for other explanations. As time
passed, we were to learn something really quite remarkable. Almost ev-
CHART 3.2: EFFECT OF DIETARY PROTEIN ON ENZYME ACTIVITY
250
76% decrease
200                                      in enzyme
>,
+-'
.;;;
activity with
'';:::;
u        150
«                                                 low-protein
a;
diets
E        100
>,
N
C
UJ
50
0
20% Protein                    5% Protein

53
TURNING OFF CANCER
CHART 3.3: DECREASE IN CARCINOGEN BINDING TO NUCLEUS
COMPONENTS CAUSED BY LOW-PROTEIN FEEDING
68% Decrease
in Chromatin 1 - - - - - - - - 1
Binding
72 % Decrease
66% Decrease
in DNA Binding
in Protein
Binding
Protein
DNA                 Chromatin
ery time we searched for a way, or mechanism, by which protein works
to produce its effects, we found one! For example, we came to discover
that low-protein diets, or their equivalents, reduce tumors by the fol-
lowing mechanisms:
• less aflatoxin entered the celF4-26
• cells multiplied more slowlyl8
• multiple changes occurred within the enzyme complex to reduce
its activity27
• the quantity of critical components of the relevant enzymes was
reduced28 , 29
• less aflatoxin-DNA adducts were formed 23 ,30
The fact that we found more than one way (mechanism) that low-
p r o t e i n diets work was eye-opening, It added a great deal of weight to
the results of the Indian researchers, It also suggested that biological
effects, although often described as operating through single reactions,
more likely operate through a large number of varied simultaneous re-
actions , very likely acting in a highly integrated and concerted manner,
Could this mean that the body had lots of backup systems in case one
was bypassed in some way? As research unfolded in the subsequent
years, the truth of this thesis became increasingly evident.
From our extensive research, one idea seemed to be clear: lower pro-
tein intake dramatically decreased tumor initiation, This finding, even
though well substantiated, would be enormously provocative for many
people.

54                             THE CHINA STUDY
PROTEIN AND PROMOTION
To go back to the lawn analogy, sowing the grass seeds in the soil was the
initiation process. We found, conclusively, through a number of experi-
ments, that a low-protein diet could decrease, at the time of planting,
the number of seeds in our "cancerous" lawn. That was an incredible
finding, but we needed to do more. We wondered: what happens during
the promotion stage of cancer, the all-important reversible stage? Would
the benefits of low protein intake achieved during initiation continue
through promotion?
Practically speaking, it was difficult to study this stage of cancer be-
cause of time and money. It is an expensive study that allows rats to live
until they develop full tumors. Each such experiment would take more
than two years (the normal lifetime of rats) and would have cost well
over $lOO,OOO (even more money today). To answer the many ques-
tions that we had, we could not proceed by studying full tumor develop-
ment; I would still be in the lab, thirty-five years later!
This is when we learned of some exciting work just published by oth-
ers3l that showed how to measure tiny clusters of cancer-like cells that
appear right after initiation is complete. These little microscopic cell
clusters were called foci.
Foci are precursor clusters of cells that grow into tumors. Although
most foci do not become full-blown tumor cells, they are predictive of
tumor development.
By watching foci develop and measuring how many there are and how
big they become,32 we could learn indirectly how tumors also develop
and what effect protein might have. By studying the effects of protein
on the promotion of foci instead of tumors we could avoid spending a
lifetime and a few million dollars working in the lab.
What we found was truly remarkable. Foci development was almost
entirely dependent on how much protein was consumed, regardless of how
much aflatOXin was consumed!
This was documented in many interesting ways, first done by my
graduate students Scott Appleton33 and George Dunaip4 (a typical com-
p a r i s o n is shown in Chart 3.4). After initiation with aflatoxin, foci grew
(were promoted) far more with the 20% protein diet than with the 5%
protein diet. 33,34
Up to this point, all of the animals were exposed to the same amount of
aflatoxin. But what if the initial aflatoxin exposure is varied? Would protein