Folate intake, alcohol consumption, cigarette smoking, and risk of colorectal adenomas.
BACKGROUND
Recent evidence suggests that folic acid (and derivatives) could contribute to the protective effect of fruits and vegetables against the risk of large-bowel cancer. Other evidence indicates that alcohol drinking and cigarette smoking may impair the biologic actions of folate. We used data from an adenoma prevention trial to investigate the occurrence of colorectal adenomas (possible precursors of colorectal cancer) in association with folate intake, alcohol consumption, and cigarette smoking.


METHODS
Patients with at least one recent large-bowel adenoma were followed with colonoscopy 1 year and 4 years after their qualifying colon examinations. Adenomas detected after the year 1 examination were used as end points. A food-frequency questionnaire was administered at study entry and at study completion; nutrient intake at study entry was used in this analysis. All statistical tests were two-sided.


RESULTS
After adjustment for caloric intake, dietary folate had a significant protective association with the risk of recurrence of large-bowel adenoma (P for trend = .04). However, this inverse association was attenuated by further adjustment for intake of dietary fiber and fat. Use of folate supplements was not associated with a reduction in risk. Alcohol intake (seven or more drinks/week) was associated with increased risk (odds ratio = 2.04; 95% confidence interval = 1.28-3.26). Cigarette smoking, even smoking for long duration, was not related to adenoma recurrence.


CONCLUSIONS
These data provide only modest support for previous findings suggesting beneficial effects of folate on colorectal adenoma risk. We find no evidence that cigarette smoking increases risk. These findings do suggest a substantial increase in risk with alcohol consumption.
Baron
J A
JA
Department of Community and Family Medicine, Dartmouth Medical School, and the Norris Cotton Cancer Center, Hanover, NH, USA. John.Baron@dartmouth.edu
Sandler
R S
RS
Haile
R W
RW
Mandel
J S
JS
Mott
L A
LA
Greenberg
E R
ER
D000236:Adenoma / Q000209:etiology*; D000368:Aged; D000428:Alcohol Drinking / Q000009:adverse effects*; D016588:Anticarcinogenic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D002986:Clinical Trials as Topic; D015179:Colorectal Neoplasms / Q000209:etiology*; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage / Q000494:pharmacology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015337:Multicenter Studies as Topic; D012306:Risk; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*
D016588:Anticarcinogenic Agents; D005492:Folic Acid