In a study of 1,953 patients with colorectal cancer and more than 4,000
disease-free patients, researchers found an association between the amount of
folate in the diet and the risk of cancer. Dr. Carlo La Vecchia, the study's
lead author, said the incidence of the disease was 40% higher for patients who
were heavy drinkers and had diets deficient in folate and the essential amino
acid methionine.
"The results are not surprising," La Vecchia told Reuters Health, "and in
broad agreement with other findings from North America."
In the study, published in a recent issue of the International Journal of
Cancer, La Vecchia and colleagues gave food questionnaires to patients with
colon or rectal cancer who were admitted to hospitals throughout Italy. Patients
admitted to the same hospitals for conditions unrelated to digestive tract
disease were also given questionnaires. They were asked to list the types of
food they ate and how much alcohol they consumed daily.
After comparing results from the surveys, those with diagnosed colorectal
cancer tended to have diets containing less folate and methionine, and were
heavier drinkers than patients who were cancer free. Light drinking meant less
than one glass of wine daily, while heavy drinking was equivalent to at least
two 12-ounce beers a day.
The main sources of folate in the Italian diets were green leafy vegetables,
whole grains, and liver. Orange juice, beans and peas are also good folic acid
sources.
Methionine levels were studied because the amino acid plays a key role in
regulating the availability of folic acid in the body. Previous studies have
shown that high levels of methionine reduce colon cancer risk in people with a
family history of the disease. Meat, fish, beans, eggs, garlic and sunflower
seeds are all natural sources of methionine.
In the current study, the researchers noted that low levels of methionine
were slightly associated with colorectal cancer, but the combination of low
methionine and low folate had an even stronger association with cancer risk.
Other studies have looked at the impact of eating fruits and vegetables on
polyp development and proliferation. Polyps are intestinal growths that can
eventually develop into colon cancer. Researchers suspect that folate may
protect against certain cancers, such as breast and colon, due to the nutrient's
role in DNA synthesis and repair.
La Vecchia said the main public health message from this study is that people
should "avoid drinking more than one or two drinks of alcoholic beverages a
day," exercise regularly, and eat a balanced diet with "lots of fruits and
vegetables."
