In the Western world, colon cancer
(also known as colorectal cancer) is the second most deadly
cancer. Each year in the United States and Europe 130,000 to
180,000 new cases are diagnosed. Slightly more men than women
develop colon cancer. A person older than 50 years has about a 5%
chance of developing colon cancer and a 2.5% chance of dying of the
disease. Unfortunately, because the treatments are so ineffective,
after 5 years only about 40% of people diagnosed are still alive.
This is a disease primarily of people consuming a diet high in meats
(including poultry and fish, dairy products, and fats; and low in
fruits and vegetables. Colon cancer arises from polyps (also called
In autopsy studies,
approximately 35% of people eating the western diet are found to
have polyps.1 Polyp formation is the consequence of
chronic irritation of mucous membrane tissues – just like callus
forms on the palm of your hand from the irritation caused by the
abrasion of hard physical work. In the case of your skin
(epidermal issue), the body’s response is the formation of layers of
protective keratin – the callus. The mucous membranes found in the
intestine, sinus cavities, and the female cervix respond to chronic
irritation by cell growth (proliferation) causing a protective mound
of tissue to form, which when large and distinct is called a polyp.
The obvious source
of that irritation in the colon is the contents of the intestine,
the remnants of the partially digested foods – and the longer and
stronger the irritation, the greater the body’s response, and the
larger the polyp. During cell division is the time when our
genetic materials – our strands of DNA – are exposed to the effects
of cancer-causing substances. Therefore, the sequence to serious
disease is as follows: irritation, cell proliferation, polyp
development, and finally, cancer. Large polyps, which are further
along this developmental sequence, are more likely to be cancerous
-- polyps less than 5mm (1/2 inch) are not likely to be cancer; at
10 mm, 1% are; and at 20 mm, 17% show cancerous changes.
The key to
preventing polyp formation, slowing their growth, preventing their
transition to cancer, and possibly, slowing the growth of the cancer
even after it is started, is to stop the irritation of the mucosa of
the intestine. In other words, your goal is to bathe the walls of
your intestine with foodstuffs as soft and gentle as fluffy mashed
Transition time from
the earliest changes in the mucous membranes to the beginning of
actual cancer takes on average 10 to 15 years.2 Fewer
than one in 20 small polyps (adenomas) will grow larger and
transform into cancer. Once the cancer begins, the time for spread
of the cancer to other parts of the body (metastasis), and obvious
disease, and finally death, takes another 10 to 20 years.
Therefore, the whole process from normal cells to cancer and death
will span on average 20 to 35 years. This is one reason colon
cancer is primarily a disease of older people.
Who gets colon
About 75% of people
diagnosed with colon cancer have no predisposing characteristics
other than they eat the rich Western diet. The other 25% have
conditions that put them at higher than average risk. These people
have inflammatory bowel disease (1%) (discussed in the November 2002
McDougall newsletter), familial adenomatous polyposis (1%), and
hereditary nonpolyposis colorectal cancer (5%). The remaining high
risk people are those with a family history of colon cancer (15 to
20%). People with one or two first-degree relatives (parents,
brothers, sisters) with colon cancer have twice the general risk of
developing colon cancer. The question that has not been fully
answered is, is this due to heredity passed on by genetics or the
fact that mother and father teach sons and daughters which foods to
like and how to cook? The learning-family-relationship emphasizes
again that the most important factor in polyp disease and colon
cancer is the contents of the colon – determined by the foods we
eat. Diet influences all stages of the development of colon cancer
from the beginnings of cell proliferation, to polyp formation, to
the final stages of cancer.
Diet Is the
In 1971 Dr. Dennis
Burkitt observed that African blacks consuming high-fiber and
low-fat, low-animal-product foods had a lower rate of death from
colon cancer, than did African whites on a low-fiber, high-fat diet.3
From this he hypothesized that diet was the cause of cancer of the
polyps and colon cancer. Further evidence on the causal
relationship of diet and cancer was made by researchers who noticed
a 50-fold variation in the incidence of this disease worldwide.4
In countries where people eat rich diets – high meat, dairy, fats,
sugars, and processed foods – there were high rates of polyps and
colon cancer. Conversely, a high intake of starches, fruits and
vegetables was associated with a low risk of these colon problems.
When people move from a county of low incidence (say a rural African
country) to a country of high incidence (the USA) they acquire the
risk for polyps and colon cancer of their new country.
experiments low-fat diets have been found to protect against these
diseases.5 Both meat and vegetable fats seem to increase
the risk of polyps and cancer. Hydrogenated fats, found in
shortenings and margarines and many kinds of prepared and packaged
foods, may be especially cancer-promoting.6 Even though
all the intricate details have not been worked out, the guilty
finger clearly points to the meat and fat, and the lack of fruits,
vegetables and dietary fiber.
There have been many
mechanisms proposed for the effects of diet on cancer development.
For example, a high-fat diet may increase the production of bile
acids from the liver. Dietary fiber will combine with and
deactivate these bile acids. In the colon, bile acids are converted
into cancer-causing substances by bowel bacteria. The kinds of
bacteria that grow in the intestine depend upon the food that is
provided them – in other words the foods that we have eaten. On a
rich diet, “unfriendly” bacteria that make cancer-causing substances
grow in the colon. These colon bacteria play several roles: they
enhance the effects of bile acids, and increase the production of
cancer-causing substances and tumor promoters.
The Role of Dietary
Fiber is the
non-digestible carbohydrates found in foods. Plant foods contain
fiber – no animal food does. Refining of plant foods removes
fiber. Fibers act by diluting and combining with cancer promoters
thus reducing their access to the colon and the rest of our body.7
Fiber is also fermented into butyric acid, which inhibits the growth
of cancer cells. There are two general classes of fiber: soluble
and insoluble. Wheat bran, which is classified as an insoluble
fiber, appears to be the most effective at preventing colon disease,
whereas soluble fibers, such as guar gum, pectin and oat bran are
less effective. Increasing dietary fiber will not only protect us
from diseases of the colon, but fiber has also been shown to
decrease cholesterol, improve insulin resistance, reduce blood
pressure and prevent heart disease.8
The Australian Polyp Prevention
Project found that a low-fat diet supplemented with wheat bran
reduced the risk of recurrence rate of large polyps (adenomas).9
One estimate suggests that if we were to increase our daily fiber
intake by 13 grams, the risk of colon cancer would decrease by 31%
(50,000 cases prevented in the USA annually).10 The
average American consumes between 8 and 14 grams of fiber a day –
all they manage to get from fiber-free animal products and refined
grains. People on the McDougall diet, like the diet of people in
rural Africa, consume 40 to 100 grams a day.
The Role of Meats:
Recent evidence from
Africans also suggests that fiber may play a smaller role than the
animal product consumption. As the modern African diet changes to
more refined foods with less fiber, the incidence of colon cancer
and polyps still remains low, probably because their diet is still
very high in carbohydrates, and low in fat and animal foods.11
Animal fat, cholesterol and protein have all been shown to have
cancer-promoting properties in animal experiments. Even chicken
and fish have been found to be associated with high rates of colon
cancer.12 The sulfur-containing amino acids, found in
high concentration in red meat, poultry, and fish, produce a large
amount of very noxious hydrogen sulfite, which has been shown to
impair cellular metabolism and mucous production.
Friendly Bacteria –
The bacteria living
in the intestine, known as the intestinal microflora, perform
vital functions for the health of the intestine and the whole body.
The addition of the right kinds of bacteria, referred to as
“friendly” bacteria, to the diets of experimental animals has been
shown to reduce their risk of developing colon cancer.13
These bacteria may provide their benefits by deactivating
cancer-causing chemicals in the colon and by replacing “unfriendly”
bacteria that produce cancer-causing substances. The kinds of
bacteria that grow in your intestine depend upon the diet you eat.
Meat, including poultry and fish, and dairy products will encourage
the growth of “unfriendly” bacteria. If you eat starches,
vegetables and fruits then the bacteria will be of the “friendly”
variety. You can also consume concentrated sources of friendly
bacteria in the form of fermented foods and pills.
products, like yogurt, are often thought of as a great source of
bacteria, like Lactobacillus, which is supposed to be healthy
for the intestine and the whole body. However, dairy products are
unhealthy for many reasons (fat, cholesterol, proteins, infectious
agents, chemical contamination, and allergy) and therefore, should
not be your source of these bacteria. In one study, increased
intake of yogurt was found to be associated with an increased risk
of having large precancerous polyps.14
The best way to get
an added dose of “friendly” bacteria is to purchase them in the form
of pills in your natural foods store – usually in the refrigerated
section. However, eating a healthy diet based on plant foods should
be your primary effort to maintain a healthy intestinal microflora –
give them the food and they will grow.
Screening for Polyps
and Colon Cancer:
In 1995, the United States
Preventative Services Task Force joined the American College of
Physicians, the National Cancer Institute, the American Cancer
Society, the World Health Organization, and the American
Gastroenterological Association in recommending screening persons
over the age of 50 years with an average risk for colon cancer.
Their recommendations are for fecal occult blood tests,
sigmoidoscopy, or both.
Since 90% of cancer
occurs after the ages of 55 years and the time required for
transition from a normal colon to cancer is between 20 to 35 years15-17,
an effective way to screen would be to do one exam between the
age of 55 and 60.18-20 This would find most of the
cancers already beginning as polyps. If no disease were present at
this time, future examinations would be unlikely to benefit the
person--since it takes so many years for a cancer to develop, and
finally to kill. (Consider, that a person would be 80 to 90 years
old to realize any benefit from exams performed after age 60 on
someone with a normal colon before 60 years old.)
Digital Rectal Examination (DRE):
Like almost all physical examination procedures, DRE has not been
tested in properly designed studies. Since the disease will be at
least 10 years old by the time its discovered, little benefit can be
Occult Blood Test:
This is one of the most controversial areas of screening. Bleeding
usually begins in the late stages of cancer, when cure is unlikely.
For every 10 people who test positive for blood, one will be found
to have cancer, four will have polyps and 5 will be normal. These
tests miss 20% to 50% of colon cancers and up to 80% of polyps.
Advocates of these tests claim screening may reduce the risk of
death by 15 to 21% over 8 to 13 years. But in actual numbers, 500
to 1,000 people may need to be tested annually for 10 years to
prevent one death from colon cancer.21 Fecal occult
blood screening is not innocuous – it can lead to anxiety, worry,
loss of insurability, social stigma, injury from future tests and
treatments, and sometimes death.22
In one often-cited study, sigmoidoscopy examination once every 10
years reduced the risk of dying from colorectal cancer by 59%.23
More frequent screening gave no better results.
Colonoscopy examination with a long flexible tube is most often
recommended for evaluation of the colon and rectum. Most
gastroenterologists are convinced that this money-making procedure
is much better24 than simpler, safer, cheaper tests;
however, their enthusiasm should be taken with caution, because the
results obtained in clinical trials may not apply to the general
practice of medicine in your community.21 Despite its
high diagnostic accuracy, colonoscopy should only be used for
screening high-risk individuals. Studies support survival benefit
for detection of precancerous polyps; but no survival benefit for
detection of actual colorectal cancers. The National Polyp Study of
more than 1,418 patients who had complete colonoscopy with one or
more polyps removed, had an incidence of colon cancer 76% to 90%
lower than expected.25 The same study showed that
screening every three years proved as beneficial as annual
alternative is a double-contrast barium enema and a flexible
sigmoidoscope, which is much lower cost with fewer complications.26-28
Colonoscopy examinations, performed by experienced
specialists, miss finding polyps 24 percent of time, and they are
much more dangerous and costly than a barium enema and a sigmoid
If you should have a
polyp found and removed, then an interval of at least three years is
recommended before a follow-up examination is performed according to
the recommendations of the National Polyp Study Workgroup, because
only a small fraction of patients were found to have adenomas
with advanced pathological features on follow-up.25
Diet May Help Even
After Polyps and Cancer Begin:
treatment of colon cancer – surgery, radiation, and/or chemotherapy
– has done little to reduce a person’s risk of dying of this
disease. Furthermore, even after the removal new polyps grow back.
The reason they regrow is the cause of the disease has not stopped –
the rich Western diet. Therefore, one of the most important, and
without a doubt, the most neglected recommendation for someone with
polys or even colon cancer, is to stop “throwing gasoline on the
fire” – change to a low-fat, unprocessed, plant-based diet.
Polyps have been
shown to regress and disappear when the fecal material is diverted
away from the colon by a surgical colostomy.30 This is
because toxic irritation of the colonic tissues caused by the
remnants of the Western diet is stopped – just like the callus in
the palm of your hand will soften and disappear when you stop hard
Could a person who
already has colon cancer benefit from a healthy diet? It has never
been tested. However, colon cancer sometimes seems to be cured
without any intervention by the doctor – a medical mystery described
as “spontaneous remission.”31 I have no doubt that a
person is much more likely to have this miracle happen to them if in
good, rather than poor, health. Even if the disease does not
completely disappear with a change in diet, there is substantial
evidence that a healthy, low-fat, no cholesterol diet, such as I
recommend, can slow the growth of cancer and allow the person to
live longer, and without a doubt, in better health. And besides, he
won’t die constipated to his added misery.
10 Steps to a
1) Center your diet
on unrefined starches
2) Add plenty of
fruits and vegetables
3) Avoid red meat,
poultry and fish
4) Avoid all kinds
of added fats
5) Add wheat bran,
especially if you do not do 1-4 above
6) Add “friendly”
bacteria (probiotics), especially if you do not do 1-4 above
7) Have one colon
exam between 55-60 years
8) Have large
polyps removed when discovered
9) Reverse the size
of polyps by eating healthy
10) Survive cancer
better with a healthy diet
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