Observational studies and polyp recurrence trials are not conclusive regarding the effects of a low-fat dietary pattern on risk of colorectal cancer.
Dr Shirley Beresford and colleagues evaluated the effects of a low-fat eating pattern on risk of colorectal cancer in postmenopausal women.
The research team undertook The Women's Health Initiative Dietary Modification Trial.
This trial was a randomized controlled trial conducted in 48,835 postmenopausal women aged 50 to 79 years.
The patients were recruited between 1993 and 1998 from 40 clinical centers throughout the United States.
The team randomly assigned 19,541 participants to the dietary modification intervention or 29,294 to the comparison group.
The intensive behavioral modification program aimed to motivate and support reductions in dietary fat.
|There were potential interactions with aspirin and combined estrogen-progestin use|
|Journal of the American Medical Association|
The program also encouraged an increase intake of vegetables and fruits, and grain servings.
The team used group sessions, self-monitoring techniques, and other tailored and targeted strategies.
Women in the comparison group continued their usual eating pattern.
The team's main outcome measure included invasive colorectal cancer incidence.
The researchers found that a total of 480 incident cases of invasive colorectal cancer occurred during a mean follow-up of 8 years.
Intervention group participants significantly reduced their percentage of energy from fat by 11% more than did the comparison group at 1 year.
This difference between groups was mostly maintained at year 6.
The team also observed statistically significant increases in vegetable, fruit, and grain servings.
Despite these dietary changes, there was no evidence that the intervention reduced the risk of invasive colorectal cancer during the follow-up period.
The researchers noted that there were 201 women with invasive colorectal cancer in the intervention group and 279 in the comparison group.
Secondary analyses suggested potential interactions with baseline aspirin use and combined estrogen-progestin use status.
The team found that colorectal examination rates, although not protocol defined, were comparable between the 2 groups.
Similar results were seen in analyses adjusting for adherence to the intervention.
Dr Beresford's team concludes, “In this study, a low-fat dietary pattern intervention did not reduce the risk of colorectal cancer in postmenopausal women during 8 years of follow-up.”