These new findings come from the Cancer Prevention Study II Nutrition Cohort, in which researchers examined the relationship between current and past use of multivitamins and the occurrence of colorectal cancer among more than 145,000 predominantly white, middle-aged or elderly adults.

This study was conducted to follow-up on a report from the Harvard Nurse's Health Study, indicating that prolonged multivitamin use might substantially reduce risk of colon cancer.

The study involved 145,000 predominantly white, middle-aged or elderly adults. At enrollment in 1992-1993, participants provided information on current use of multivitamins.

All of the subjects had also provided information on multivitamin use some 10 years earlier in 1982, as part of another study. This allowed the investigators to examine the potential effects of past use of vitamins, without relying on what people recalled.

Roughly half of the group reported no multivitamin use, 8% said they took a multivitamin regularly (four or more times per week) only in the past, and 19% said they regularly took a multivitamin only recently.

During follow-up from 1992 to 1997, 797 cases of colorectal cancer were detected.