Calcium and fibre supplementation in prevention of colorectal adenoma recurrence: a randomised intervention trial

Background Some epidemiological studies have suggested that high dietary in take of calcium and fibre reduces colorectal carcinogenesis. Available data are not sufficient to serve as a basis for firm dietary advice. We underto ok a multicentre randomised trial to test the effect of diet supplementatio n with calcium and fibre on adenoma recurrence. Methods We randomly assigned 665 patients with a history of colorectal aden omas to three treatment groups, in a parallel design: calcium gluconolactat e and carbonate (2 g elemental calcium daily), fibre (3.5 g ispaghula husk) , or placebo. Participants had colonoscopy after 3 years of followup. The p rimary endpoint was adenoma recurrence. Analyses were by intention to treat . Findings 23 patients died, 15 were lost to follow-up, 45 refused repeat col onoscopy, and five developed severe contraindications to colonoscopy. Among the 552 participants who completed the follow-up examination, 94 slopped t reatment early. At least one adenoma developed in 28 (15.9%) of 176 patient s in the calcium group, 58 (29.3%) of 198 in the fibre group, and 36 (20.2% ) of 178 in the placebo group. The adjusted odds ratio for recurrence was 0 .66 (95% CI 0.38-1.17. p=0.16) for calcium treatment and 1.67 (1.01-2.76, p =0.042) for the fibre treatment. The odds ratio associated with the fibre t reatment was significantly higher in participants with baseline dietary cal cium intake above the median than in those with intake below the median (in teraction test, p=0.028) Interpretation Supplementation with fibre as ispaghula husk may have advers e effects on colorectal adenoma recurrence, especially in patients with hig h dietary calcium intake. Calcium supplementation was associated with a mod est but not significant reduction in the risk of adenoma recurrence.