The effect of alpha-tocopherol and beta-carotene supplementation on colorectal adenomas in middle-aged male smokers.
Epidemiological and experimental studies have indicated that dietary factors such as vitamin C, vitamin E, and beta-carotene are associated with the risk of colorectal cancer. This study was carried out within the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study (ATBC Study), whose participants were randomly assigned to four supplementation groups: (a) alpha-tocopherol (AT), 50 mg/day; (b) beta-carotene (BC), 20 mg/day; (c) both AT and BC; and (d) placebo. We included the 15,538 ATBC Study participants who had been randomized within the areas of three major cities in southern Finland. Cases of colorectal adenoma (n = 146) were identified by the pathology laboratories in the study areas, and these participants' medical records were collected and reviewed. Alpha-tocopherol supplementation increased the risk for adenomas (relative risk, 1.66; 95% confidence interval, 1.19-2.32), whereas beta-carotene supplementation had no effect on the risk (relative risk, 0.98; 95% confidence interval, 0.71-1.35). Slightly more prediagnosis rectal bleeding and intestinal pain occurred in those adenoma cases who received alpha-tocopherol supplements than in those who did not. Thus, some bias may have resulted, with alpha-tocopherol supplementation leading to more colonoscopies and, thus, to an increased detection of incident polyps in this group. This is further supported by the trial finding that alpha-tocopherol supplementation did not increase the risk of colorectal cancer.
Malila
N
N
Department of Nutrition, National Public Health Institute, Helsinki, Finland.
Virtamo
J
J
Virtanen
M
M
Albanes
D
D
Tangrea
J A
JA
Huttunen
J K
JK
D000236:Adenoma / Q000453:epidemiology / Q000209:etiology / Q000517:prevention & control*; D000368:Aged; D000975:Antioxidants / Q000627:therapeutic use*; D015982:Bias; D015179:Colorectal Neoplasms / Q000453:epidemiology / Q000209:etiology / Q000517:prevention & control*; D004311:Double-Blind Method; D004359:Drug Therapy, Combination; D005387:Finland / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*; D014810:Vitamin E / Q000627:therapeutic use*; D019207:beta Carotene / Q000627:therapeutic use*
D000975:Antioxidants; D019207:beta Carotene; D014810:Vitamin E