The China Study (26 page)

168                          THE CHINA STUDY
levels of plant eaters may crash from forty to fifteen, rather than
sixty to fifteen for animal eaters.
• These abrupt hormone changes in the body are what cause meno-
pausal symptoms.
• Therefore, a plant-based diet leads to less severe hormone crash
and a gentler menopause.
This argument is eminently reasonable based on what we know, al-
t h o u g h more studies would be helpful. But even if future studies fail to
confirm these details, a plant-based diet still offers the lowest risk for
both breast cancer and heart disease for other reasons. It might just be
the best of all worlds, something that no drug can offer.
In each of the various issues involving breast cancer risk (tamoxifen
use, HRT use, environmental chemical exposure, preventive mastec-
tomy), I am convinced that these practices are distractions that prevent
us from considering a safer and far more useful nutritional strategy. It is
critical that we change the way we think about this disease, and that we
provide this information to the women who need it.
LARGE BOWEL CANCER
(INCLUDING COLON AND RECTUM)
At the end of June 2002, George W Bush handed the presidency over to
Dick Cheney for a period of roughly two hours while he underwent a
colonoscopy. Because of the implications President Bush's colonoscopy
had for world politics, the story made national news, and colon and rec-
tal screening were briefly thrust into the spotlight. Across the country,
whether the comedians were making jokes or the news anchors were
describing the drama, everybody was suddenly, briefly, talking about
this thing called a colon os copy and what it was for. It was a rare mo-
m e n t in which the country turned its focus to some of the most prolific
killer diseases , colon and rectal cancers.
Because colon and rectal cancers are both cancers of the large bowel,
and because of their other similarities, they often are grouped together
under the term colorectal cancer. Colorectal cancer is the fourth most
common cancer worldwide, in terms of overall mortality.60 It is the sec-
o n d most common in the United States, with 6% of Americans getting the
cancer during their lifetime. 3 ? Some even claim that, by age seventy, one-
half of the population of "Westernized" countries will develop a tumor in
the large bowel and lO% of these cases will progress to a malignancy.6l

( 0 MM0 N (A N( ERS: BREA ST,P R0 STATE l ARGE BOW E l l 69
I
GEOGRAPHIC DISPARITY
North America, Europe, Australia and wealthier Asian countries Qa-
p a n , Singapore) have very high rates of colorectal cancer, while Africa,
Asia and most of Central and South America have very low rates of this
cancer. For example, the Czech Republic has a death rate of 34.19 per
100,000 males, while Bangladesh has a death rate of 0.63 per 100,000
males! 62,63 Chart 8.3 shows a comparison of average death rates between
more developed countries and less developed countries; all these rates
are age-adjusted.
The fact that rates of colorectal cancer vary hugely between countries
has been known for decades. The question has always been why. Are the
differences due to genetics, or to environment?
It seems that environmental factors, including diet, play the most
important roles in colorectal cancer. Migrant studies have shown that
as people move from a low-cancer risk area to a high-cancer risk area,
they assume an increased risk within two generations. 64 This suggests
that diet and lifestyle are important causes of this cancer. Other stud-
ies have also found that rates of colorectal cancer change rapidly as a
population's diet or lifestyle changes. 64 These rapid changes in cancer
rates within one population cannot possibly be explained by changes in
inherited genes. In the context of human society, it takes thousands of
CHART 8.3: COLORECTAL CANCER DEATH RATE IN "MORE
DEVELOPED" COUNTRIES AND "LESS DEVELOPED" COUNTRIES
18
16
Death
14
Rate per
12
100,000                                                        .Male
10
People
Female
[J
8
(age-
6
adjusted)
4
2
0
More                  Less
Developed             Developed
Countries             Countries

THE CHINA STUDY
170
years to get widespread, permanent changes in the inherited genes that
are passed from one generation to the next. Clearly, something about
environment or lifestyle is either preventing or enhancing the risk of
getting colorectal cancer.
In a landmark paper published almost thirty years ago, researchers
compared environmental factors and cancer rates in thirty-two coun-
tries around the world. 65 One of the strongest links between any cancer
and any dietary factor was between colon cancer and meat intake. Chart
8. 4 shows this link for women in twenty-three different countries.
In this report, countries where more meat, more animal protein, more
sugar and fewer cereal grains were consumed had far higher rates of
colon cancer.65 Another researcher whom I mentioned in chapter four,
Denis Burkitt, hypothesized that intake of dietary fiber was essential for
digestive health in general. He compared stool samples and fiber intakes
in Africa and Europe and proposed that colorectal cancers were largely
the result of low fiber intake. 66 Fiber, remember, is only found in plant
foods. It is the part of the plant that our body cannot digest. Using data
from another famous study that compared diets in seven different coun-
tries, researchers found that eating an additional ten grams of dietary
fiber a day lowered the long-term risk of colon cancer by 33%.67 There
are ten grams of fiber in one cup of red raspberries, one Asian pear or
CHART 8.4: FEMALE COLON CANCER INCIDENCE
AND DAILY MEAT CONSUMPTION
50
I:
GJ
E
~                                                                          NEW ZEALAND.
o
o
o
g                                                                            • U.S.A.
....
• CANADA
-- 3 0
GJ
v
I:
DENMARK
GJ
-c
'u                                                   •      .UK
SWEDEN
.E                                           •• NETHERLANDS
...                             NORWAY                  FDR
~                                   •     .ISRAEL      • • ICELAND
I:
JAMAICA                       •
III
•        FINLAND PUERTO RICO GERMANY
10
U
~
YUGOSLAVIA.             • •POLAND
I:
o
JAPAN.      CHILE •    ROMANIA .HUNGARY
"0
u             .NIGERIA       • COLOMBIA
o
o      40       80                           200         240     280        320
120       160
Per Capita Daily Meat Consumption (grams)

COMMON CANCERS: BREAST, PROSTATE, LARGE BOWEl                171
one cup of peas. A cup of just about any variety of bean would provide
significantly more than ten grams of fiber.
From all this research, it seems clear that something can be said for
the importance of diet in colorectal cancer. But what exactly stops colon
and rectal cancer? Is it fiber? Is it fruits and vegetables? Is it carbohy-
drates? Is it milk? Each of these foods or nutrients has been suggested to
playa role. The debate has raged, and solid answers are seldom agreed
upon.
THE SPECIFIC CURE
Most of the debate over the past twenty-five years on dietary fiber and
its link to large bowel cancer began with Burkitt's work in Africa. Be-
cause of Burkitt's prominence, many people have believed that fiber is
the source of colorectal health. Perhaps you have already heard that
fiber is good for preventing colon cancer. At least you probably have
heard that fiber "keeps things running well." Isn't that what prunes are
known for?
Yet nobody has ever been able to prove that fiber is the magic bullet
for preventing colorectal cancer. There are important technical reasons
why a definitive conclusion regarding fiber is difficult to make. 68 Each
of these reasons is related either directly or indirectly to the fact that
dietary fiber is not a Single, simple substance producing a single, simple
benefit. Fiber represents hundreds of substances, and "its" benefits
operate through an exceptionally complex series of biochemical and
physiological events. Each time researchers assess the consumption
of dietary fiber, they must decide which of the hundreds of fiber sub-
fractions to measure and which methods to use. It is nearly impossible
to establish a standard procedure because it is virtually impossible to
know what each fiber sub-fraction does in the body.
The uncertainty of having a standard procedure prompted us to
measure fiber in more than a dozen ways in our China Study. As sum-
marized in chapter four, as consumption of almost all of these fiber
types went up, colon and rectal cancer rates went down.69 But we could
make no clear interpretations 70 as to which type of fiber was especially
important.
Despite the uncertainties, I continue to believe that Burkitt's66 ini-
tial hypothesis that fiber-containing diets prevent colorectal cancers is
correct and that some of this effect is due to the aggregate effect of all
the fiber types. In fact, the hypothesis that dietary fiber prevents large

THE CHINA STUDY
172
bowel cancers has become even more convincing. In 1990, a group of
researchers reviewed sixty different studies that had been done on fiber
and colon cancer.71 They found that most of the studies supported the
idea that fiber protects against colon cancer. They noted that the com-
b i n e d results showed that the people who consumed the most fiber had
a 43% lower risk of colon cancer than the people who consumed the
least fiber.71 Those who consume the most vegetables had a 52% lower
risk than those who consume the least vegetables. 71 But even in this
large review of the evidence, researchers noted, "the data do not permit
discrimination between effects due to fiber and non-fiber effects due to
vegetables."71 So is fiber, all by itself, the magic bullet we've been look-
i n g for? We still, in 1990, didn't know.
Two years later, in 1992, a different group of researchers reviewed
thirteen studies that had compared people with and without colorectal
cancer (case-control design).72 They found that those who had con-
s u m e d the most fiber had a 47% lower risk of colorectal cancer than
those who consumed the least. 72 In fact, they found that if Americans
ate an additional thirteen grams of fiber a day from food sources (not as
supplements), about a third of all colorectal cancer cases in the u.S.
could be avoided.72 If you'll remember, thirteen grams, in real world
terms, is the amount found in about a cup of any variety of beans.
More recently, a mammoth study called the EPIC study collected
data on fiber intake and colorectal cancer in 519,000 people across
Europe.7 They found that the 20% of people who consumed the most
3
fiber in their diet, about thirty-four grams per day, had a 42% lower risk
of colorectal cancer than the 20% who consumed the least fiber in their
diet, about thirteen grams per day.73 It's important to note once again
that, as with all of these studies, dietary fiber was obtained in food, not
as supplements. So all we can say is "fiber-containing diets" seem to sig-
nificantly reduce the risk of colorectal cancer. We still can't say anything
definitive about isolated fiber itself. This means that attempts to add
isolated fiber to foods may not produce benefits. But consuming plant
foods naturally high in fiber is clearly beneficial. These foods include
vegetables (the non-root parts), fruits and whole grains.
In reality, we can't even be sure how much of the prevention of
colorectal cancer is due to fiber-containing foods , because as people
eat more of these foods they usually consume less animal-based foods.
In other words, are fruits, vegetables and whole grains protective, or is
meat dangerous? Or is it both? A recent study in South Africa helped

COMMON CANCERS: BREAST, PROSTATE, LARGE BOWEL              173
to answer these questions. White South Africans have seventeen times
more large bowel cancer than black South Africans, and this was first
thought to be due to the much higher consumption of dietary fiber
among black South Africans provided by unrefined maize. 74 However,
in more recent years, black South Africans have been increasingly con-
s u m i n g commercially refined maize-meal-maize minus its fiber. They
now eat even less fiber than the white South Africans. Yet, colon cancer
rates among blacks remain at a low level,15 which calls into question
how much of the cancer-protective effect is due to dietary fiber alone.
A more recent study76 showed that the higher colon cancer rates among
white South Africans could well be due to their elevated consumption
of animal protein (77 vs. 25 g/day), total fat (ll5 vs. 71 g/day) and
cholesterol (408 vs. 2ll mg/day), as seen in Chart 8.5 . The researchers
suggested that the much higher colon cancer rates among white South
CHART 8.5: INTAKE OF ANIMAL PROTEIN, TOTAL FAT AND
CHOLESTEROL AMONG BLACK AND WHITE SOUTH AFRICANS
450
400
350
300
Daily Intake 250                                     • Black SA
(milligra ms) 200
o White SA
150
100
50
Cholesterol
120
100
80
Daily Intake    60
(Grams)
40
20
o
Animal Protein             Total Fat

174                          THE CHINA STUDY
Africans may be more related to the quantity of animal protein and fat in
their diets than their lacking the protective factor of dietary fiber. 76
What is clear is that diets naturally high in fiber and low in animal-
based foods can prevent colorectal cancer. Even in the absence of more
specific details, we can still make important public health recommenda-
tions. The data clearly show that a whole foods, plant-based diet can dra-
matically lower colorectal cancer rates . We don't need to know which fiber
is responsible, what mechanism is involved or even how much of the effect
is independently due to fiber.
OTHER FACTORS
It has been recently noted that the same risk factors that promote
colorectal cancer, a diet low in fruits and vegetables and high in animal
foods and refined carbohydrates, can also promote insulin resistance
syndrome.77- 79 From there, scientists have hypothesized that insulin re-
sistance may be responsible for colon cancer.77- 8 2 Insulin resistance was
described in chapter six as a diabetic condition. And what's good for
keeping insulin resistance under control is also good for colon cancer: a
diet of whole, plant-based foods .
This diet happens to be very high in carbohydrates, which have
recently been under assault in the marketplace. Because carbohydrate-
confusion persists, let me remind you that there are two different types
of carbohydrates: refined carbohydrates and complex carbohydrates.
Refined carbohydrates are the starches and sugars obtained from plants
by mechanically stripping off their outer layers, which contain most of
the plant's vitamins, minerals, protein and fiber. This "food" (regular
sugar, white flour, etc.) has very little nutritional value. Foods such as
pastas made from refined flour, sugary cereals, white bread, candies and
sugar-laden soft drinks should be avoided as much as possible. But do
eat whole, complex carbohydrate-containing foods such as unprocessed
fresh fruits and vegetables, and whole grain products like brown rice
and oatmeal. These unprocessed carbohydrates, especially from fruits
and vegetables, are exceptionally health-promoting.
You also may have heard that calcium is beneficial in fighting colon
cancer. This, of course, gets extended to the argument that cow's milk
fights colon cancer. It has been hypothesized that high-calcium diets
prevent colon cancer in two ways: first, it inhibits the growth of critical
cells in the colon,s3.s4 and second, it binds up intestinal bile acids. These
bile acids arise in the liver, move to the intestine and are thought to get