A diet containing little alcohol that is rich in folate sources like green leafy vegetables, fruits and whole grains may lower the risk for colorectal cancer, according to researchers in Italy.
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.
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.
In the study, the researchers 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.
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 growth. 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.
The researchers 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."
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