Level 2: Mid-level evidence

Prunes (dried plums) have long been considered effective for constipation and are the most common food that people associate with an anti-constipation effect. However, there has been little direct evidence to evaluate the efficacy of prunes as a dietary treatment or to compare prunes with other treatments for constipation. A recent trial, supported by the California Dried Plum Board, provides some comparative efficacy evidence (Aliment Pharmacol Ther. 2011;33:822-828).

Forty adults (37 women) with chronic constipation were studied in a randomized crossover trial with blinding of the outcome assessors. Participants had mild to moderate constipation; those with comorbidities, alarm symptoms, or irritable bowel syndrome were excluded. Treatment periods lasted three weeks, separated by a one-week washout period.

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One treatment period used prunes 50 g (about six prunes) twice daily with meals; the other treatment period used psyllium 11 g twice daily with eight ounces of water. Prunes were more effective than psyllium using measures of number of complete spontaneous bowel movements (3.4 vs. 2.8 per week, P=0.006) or stool consistency (P=0.02). Improvement in global constipation symptoms (the most clinically relevant outcome) was reported by 70% with prunes and by 55% with psyllium, but this difference was not statistically significant. There were no significant differences between treatments in palatability, satiety, bloating or adverse events.