Adherence to a Low-Fat, High-Fiber Diet Lowers Risk of Polyp Recurrence

From Reuters Health Information

Sep 04 - Patients who strictly follow a low-fat, high-fiber, and high-fruit and -vegetable diet have a lower risk of colon adenoma recurrence.

"The Polyp Prevention Trial was designed to test the effect of (this) dietary intervention on the recurrence of adenomas in the colon," Dr. Leah B. Sansbury of the National Cancer Institute, Bethesda, Maryland, and colleagues write in the September issue of the American Journal of Epidemiology.

The authors note that the goals of the dietary intervention were to limit fat to 20% of energy intake and to consume at least 18 g of fiber and 3.5 servings of fruits and vegetables per 1000 kcal.

"After 4 years of the trial, no difference in the rate of adenoma recurrence between the intervention group and the control group was observed," they note. "The number of dietary goals met by the intervention group varied greatly; thus, it is possible that lack of adherence in fully attaining the intervention goals may account for the lack of observed effect."

The researchers examined data from the Polyp Prevention Trial to determine whether strict adherence to the low-fat, high-fiber, and high-fruit and -vegetable intervention goals influenced the risk of adenoma recurrence. Included were 1095 subjects recruited between 1991 and 1994 (control group, n = 947; intervention group, n = 958). Annual food-frequency questionnaires were used to assess dietary intake and supplement use.

Colonoscopies were performed at baseline, the 1-year visits, and the end of the trial intervention.

Of 821 participants in the intervention group who completed the study, 245 (29.8%) were classified as poor compliers, 366 (44.6%) as inconsistent compliers, and 210 (25.6%) as super compliers. Subjects classified as super compliers consistently reported that they met or exceeded each of the dietary goals at all four annual visits.

In unadjusted analyses, super compliers had a 30% statistically significant decreased odds of adenoma recurrence compared with controls (odds ratio = 0.69). The association remained unchanged in fully adjusted models. Strict compliance to the intervention over the entire 4 years led to a nearly 50% statistically significant decreased odds of multiple adenomas. A nonsignificant inverse association was observed for multiple and advanced adenoma recurrence.

"To focus on testing the biologic effects of an intervention or treatment on the trial, future dietary and treatment trials could target and randomize individuals most likely to comply," Dr. Sansbury and associates conclude. "Findings from such trials would enhance the validity of our own findings."

Am J Epidemiol 2009;170:576-584.