We investigated the association between self-reported alcohol ingestion and colorectal cancer in a cohort of male smokers in Finland. Among 27,109 men aged 50 to 69 years, 87 colon and 53 rectal cases were diagnosed during the five to eight years of follow-up. Among drinkers, colorectal cancer risk increased with the amount of alcohol consumed (P trend = 0.01) with risk increasing by 17 percent for each drink consumed. Both beer and spirits contributed to this increased risk. Further analyses revealed that the positive association with alcohol was primarily for colon cancer (P trend = 0.01). Interestingly, risk of colorectal cancer associated with drinking (cf self-reported abstinence) changed with follow-up time, suggesting an inverse association for alcohol early in follow-up, and a positive association after about three-and-a-half years of follow-up. Follow-up time did not modify the positive association with amount of alcohol among drinkers, however. Results also indicated that beta-carotene supplementation may attenuate the effect of alcohol on colorectal cancer risk among drinkers. In conclusion, this study supports a role for alcohol in colon carcinogenesis and suggests that similar studies should evaluate carefully the effects of lifetime drinking habits and recent abstinence.
Evidence is accumulating that folate, a B vitamin found in green leafy vegetables, may affect the development of neoplasia. We examined the relationship between folate status and colorectal cancer in a case-control study nested within the Alpha-Tocopherol Beta-Carotene Study cohort of male smokers 50-69 years old. Serum folate was measured in 144 incident cases (91 colon, 53 rectum) and 276 controls matched to cases on baseline age, clinic, and time of blood collection. Baseline dietary folate was available from a food-use questionnaire for 386 of these men (92%). Conditional logistic regression modeling was used. No statistically significant association was observed between serum folate and colon or rectal cancer. Although a 2-fold increase in rectal cancer risk was suggested for men with serum folate > 2.9 ng/ml and those in the highest quartile of energy-adjusted folate intake, there was no evidence of a monotonic dose-response, and all confidence intervals included unity. For dietary folate and colon cancer, odds ratios of 0.40 [95% confidence interval (CI), 0.16-0.96], 0.34 (95% CI, 0.13-0.88), and 0.51 (95% CI, 0.20-1.31) were obtained for the second through fourth quartiles of energy-adjusted folate intake, respectively, compared to the first (P for trend = 0.15). Furthermore, men with a high-alcohol, low-folate, low-protein diet were at higher risk for colon cancer than men who consumed a low-alcohol, high-folate, high-protein diet (OR, 4.79; 95% CI, 1.36-16.93). This study suggests a possible association between low folate intake and increased risk of colon cancer (but not rectal cancer) and highlights the need for further studies that measure dietary folate and methionine, along with biochemical measures of folate (i.e., erythrocyte and serum), homocysteine, and vitamin B12.
The authors conducted a dietary methodology study in 1984 in Finnish men aged 55-69 years in order to validate two dietary assessment instruments being used in the US-Finland Alpha-Tocopherol, Beta-Carotene Lung Cancer Prevention Trial. Twelve 2-day food records collected from 162 men over a 6-month period, including every day of the week, served as the reference measure. This report focuses on three important questions for investigating diet and disease relations: 1) How many days are necessary to classify "usual" intake? 2) Is there loss as a result of using consecutive days? 3) Which days are necessary for assessment and classification of "usual" diet? A repeated-measures regression model was used to estimate the variance components and the effects of consecutive days, weekday (weekday vs. weekend), and season. Correlations between the averages of different numbers of days of food records and "true" usual intake were examined along with the resulting attenuations in relative risk. Results suggest that 7-14 days are required to adequately classify most individuals into categories of intake for most nutrients and some foods. There appears to be some loss of information from using consecutive days rather than days further apart. Weekday/weekend differences in mean intakes are slight, and the rank ordering of individuals appears to be preserved. A moderate seasonal effect is shown for classification of fruits, but only a slight one is seen for micronutrients and berries. Implications for the design of epidemiologic and validation studies are discussed.