Tufts University, July 2, 2001 (Reviewed: July
5, 2003)
A link between diet and colon cancer?
Scientists have long suspected that diet may affect the
occurrence of colorectal cancer, but they've had a tough time determining
exactly what factors in foods might make a person less likely to develop
the intestinal polyps, or growths, that can progress to cancer. Several
large studies have failed to find such a protective role for fruits and
vegetables. But a study just published in the Journal of the National
Cancer Institute suggests that adding some fruits and vegetables
to an otherwise produce-poor diet might make a difference.
A recent analysis
Swedish researchers collected diet information on more
than 61,000 women ages 40 to 74 enrolled in a national health survey.
They then kept track of the women for almost 10 years, noting the number
who developed colorectal cancer during that time. The researchers found
that the women who consumed more than five servings a day of fruits and
vegetables a day were about 25% less likely to develop colorectal cancer
when compared to those who ate less than 2.5 servings per day.
And, taking a closer look at those in the lowest intake
group, those who ate less than 1.5 servings per day were more likely
to develop colorectal cancer than those who ate an average of 2.5 servings
per day.
Did diet make a difference?
These results seem to suggest that a daily diet that includes
several servings of fruits and vegetables can reduce the risk of colorectal
cancer in some women. But other large studies, including the US-based
Nurses' Health Study, have not come to the same conclusion. Why the difference?
The authors of the Swedish study point out that vitamin
supplements and folic acid-fortified foods -- common in the United States,
but not as widely used in Sweden -- provide additional amounts of some,
though certainly not all, of the nutrients found in fruits and vegetables,
and may provide an "extra layer" of protection from disease.
On the other hand, adding a few servings a day to a diet otherwise short
on fruits and vegetables could makes a significant health difference
to people who don't routinely consume vitamin supplements and fortified
foods.
Advice to consumers
Does that mean that those of us who take a daily multivitamin
don't need to pay attention to what's on our plate? No - the American
Cancer Society reminds consumers that even the most healthful foods can't
totally insulate them from disease. While nutritionists can't promise
that a produce-rich diet will reduce your risk of colorectal cancer,
they do know that there are plenty of benefits to a diet that provides
generous amounts of fruits and vegetables.
An estimated 90% of all cases of colorectal cancer are
diagnosed in people older than 50, but the disease process takes many
years to develop. Eating well-choosing a diet low in fat, high in fiber,
and one that includes at least five servings a day of fruits and vegetables-is
something that everyone can do, and it may just reduce their risk of
many types of cancer, including colorectal cancer.
Source
Fruit, vegetables, dietary fiber, and risk of
colorectal caner. P. Terry, E. Giovannucci, KB. Michels,
et al., Journal of the National Cancer Institute, 2001, vol. 93,
pp. 525--533