Results from two repeated 5 day dietary records with a 1 y interval among patients with colorectal polyps

Dietary factors are known to be associated with initiation and development of colorectal cancer (CRC), and also with CRC's major precursor, the colorectal polyp. In long-term intervention studies on colorectal polyps, dietary changes may therefore affect potential effects of the study intervention.

To examine potential dietary changes among polyp-patients randomly selected from a 3 y intervention study after 1 y.

Of 116 polyp-bearing out-patients (50% men), aged 50-76 y, who participated in the double-blind 3 y placebo-controlled endoscopic follow-up and intervention study against growth and recurrence of polyps, 30 patients were randomised (strata: sex, age and polyp size) to perform a repeated 5 day dietary record by weighing after 1 y. The patients received a daily mixture of vitamin C (150 mg), alpha-tocopherol (75 mg), beta-carotene (15 mg), selenium (101 microg) and calcium (1.6 g) or placebo (lactose) for a period of 3 y with annual colonoscopic examinations and polyps size measurements to test if the mixture was able to reduce polyp growth and recurrence. Polyps of >9 mm were removed, whereas the remainders and new discoveries of polyps <9 mm were left in situ until the end of the study.

Twenty-nine patients agreed to perform the repeated 5 day dietary record, and 86% performed the second record within 48-58 weeks after the first record. The results showed that, with the exception of vitamin D, milk and milk products, no significant differences were found between the two records. The median value of the Spearman's correlation coefficient for energy and energy-yielding nutrients was 0.66, for vitamins and minerals 0.58, and for foods 0.58. Individual differences between the records were found for most variables, but most of these were negligible.

After 1 y, no major dietary changes were found which could be associated with a changed susceptibly for malignancy, and thereby affect potential effects of the study intervention. We may thus suggest that a potential changed susceptibility towards growth and recurrence of polyps, is due to the specific intervention, and not due to other major dietary changes.