"Solving a Colon Cancer Mystery"
Colorectal cancer is the second leading cause
of cancer death in the United States, after lung cancer.
If you look at the rates of lung cancer around the world,
they vary by a factor of 10.
If there was nothing we could do to prevent lung cancer,
if it just rose spontaneously, happened at random,
you'd assume that the rates everywhere would be the same,
but since there's such a huge variation in rates
you assume there's some external cause,
and indeed we now know smoking is responsible
for 90% of lung cancer cases.
So if we don't want to die of the #1 cancer killer,
by just not smoking we can throw 90% of our risk out the window.
For colon cancer there's an even bigger spread,
bigger variation around the world.
So it appears colon cancer doesn't just happen,
something makes it happen.
Well, if our lungs can get filled with carcinogens from smoke,
maybe our colons are getting filled with carcinogens from food.
Researchers from the University of Pittsburgh
and the University of Limpopo sought to answer the question,
'Why do African Americans get more colon cancer than native Africans?'
Why study Africans?
Because colon cancer is extremely rare in native African populations,
like more than 50 times lower than rates of Americans, white or black.
It's the fiber, right?
Dr. Burkitt was the first to describe the low incidence of colon cancer
in native Africans, ascribing it to their traditional staple diet
that was high in whole grains and, therefore, fiber content.
Seems you get about a 10% reduction in risk for every 10 grams of fiber a day.
So, hey, if it's a 1% drop for each gram,
and they're eating upwards of 100 grams a day,
well, that could explain why colon cancer is so rare in sub-Saharan Africa.
But wait a second, the modern African diet
is highly processed, low in fiber,
and yet there has been no dramatic increase in colon cancer incidence.
The modern African diet has a low fiber content
as most populations now depend on
commercially produced refined cornmeal.
And we're not just talking low fiber intake,
we're talking United States of America low,
down around half the recommended daily allowance.
Yet colon disease still remains rare, still 50 times less colon cancer.
Maybe it's because they're thinner and exercise more?
No, they're not, and no, they don't.
If anything their physical activity levels may now be even lower.
So if they're sedentary like us, eating mostly refined carbs,
few whole plant foods, little fiber -- like us,
why do they still have 50 times less colon cancer than us?
Well, there is one difference.
The diet of both African Americans and Caucasian Americans
is rich in meat, whereas the native Africans' diet
is so low in meat and saturated fat they have total cholesterol levels
averaging 139, compared to over 200 in the U.S.
So, yes, they don't get a lot of fiber anymore,
but they continue to minimize meat and animal fat consumption
supporting evidence that perhaps the most powerful determinants
of colon cancer risk are the levels of meat and animal fat intake.
So why do Americans get more colon cancer than Africans?
Maybe the rarity of colon cancer in Africans is not the fiber,
but their low animal product consumption.
There is a divergence of opinion as to whether it's the animal fat,
cholesterol, or animal protein that's most responsible
for the increased cancer risk, as all three have been shown
to have carcinogenic cancer causing properties, but it may not really matter
which component is worse, as a diet rich in one is usually rich in the others.