A Cochrane review «»1 «Alonso-Coello P, Guyatt G, Heels-Ansdell D ym. Lax...»1 included 7 studies with a total of 378 subjects. The types of fiber studied were Ispaghula husk (three trials), plantago ovata or psyllium (two trials), sterculia (one trial) and unprocessed bran (one trial). Overall symptoms from the hemorrhoids were relieved by 53% in the fiber group (risk reduction (RR) 0.47, 95% CI 0.32 to 0.68). The effect on bleeding showed a significant difference in favour of the fiber (RR 0.50, 95% CI 0.28 to 0.89). Studies including data on multiple follow-ups (usually after six weeks and three months) showed consistent results over time. Evidence was downgraded by the risk of publication bias and only moderate study quality.
In a randomized study (n=50) patients with internal bleeding hemorrhoids received either a preparation of Plantago ovata or placebo «Perez-Miranda M, Gomez-Cedenilla A, León-Colombo T...»2. During the 15 days of treatment the average number of bleeding episodes was 4.8 in the study group versus 6.4 in the control group. During the following 15 days, the number of bleeding episodes was 3.1 in the study group compared with 5.5 in the control group (p < 0.05). The number of congested hemorrhoidal cushions diministed from 2.6 to 1.6 after fibre treatment (p < 0.01); no differences were found in the control group.
Comment: The quality of evidence is downgraded by sparse data.