Fermented Fiber Supplements Are No Better Than Placebo for a Laxative Effect.
Misconceptions about the effects of dietary fiber and 'functional' fiber on stool parameters and constipation persist in the literature.



A comprehensive literature review was conducted with the use of the Scopus and PubMed scientific databases to identify and objectively assess well-controlled clinical studies that evaluated the effects of fiber on stool parameters and constipation.



The totality of well-controlled randomized clinical studies show that, to exert a laxative effect, fiber must: (1) resist fermentation to remain intact throughout the large bowel and present in stool, and (2) significantly increase stool water content and stool output, resulting in soft/bulky/easy-to-pass stools. Poorly fermented insoluble fiber (e.g., wheat bran) remains as discreet particles which can mechanically irritate the gut mucosa, stimulating water & mucous secretion if the particles are sufficiently large/coarse. For soluble fibers, some have no effect on viscosity (e.g., inulin, wheat dextrin) while others form high viscosity gels (e.g., β-glucan, psyllium). If the soluble fiber is readily fermented, whether non-viscous or gel-forming, it has no effect on stool output or stool water content, and has no laxative effect. In contrast, a non-fermented, gel-forming soluble fiber (e.g., psyllium) retains its gelled nature and high water-holding capacity throughout the large bowel, resulting in soft/bulky/easy-to-pass stools.



When considering a recommendation for a fiber supplement regimen to treat and/or prevent constipation, it is important to consider which fibers have the physical characteristics to exert a laxative effect, and which fiber supplements have rigorous clinical evidence of a significant benefit in patients with constipation.
Global Clinical Sciences, Procter & Gamble, Mason Business Center, 8700 Mason-Montgomery Road, Mason, OH, 45040, USA. mcrorie.jw@pg.com.
Johnson W
JW
McRorie
University of Michigan Health System, 1500 E Medical Center Dr, Ann Arbor, MI, 48109, USA.
William D
WD
Chey
D003248:Constipation / Q000188:drug therapy / Q000517:prevention & control*; D003912:Dextrins / Q000627:therapeutic use; D004043:Dietary Fiber / Q000627:therapeutic use*; D019587:Dietary Supplements; D005285:Fermentation; D005936:Glucans / Q000627:therapeutic use; D006801:Humans; D007444:Inulin / Q000627:therapeutic use; D054368:Laxatives / Q000627:therapeutic use*; D011620:Psyllium / Q000627:therapeutic use; D047071:beta-Glucans / Q000627:therapeutic use
D003912:Dextrins; D004043:Dietary Fiber; D005936:Glucans; D054368:Laxatives; D047071:beta-Glucans; D011620:Psyllium; D007444:Inulin; C033375:polydextrose
Ferment; Fiber; Laxative; Placebo; Stool; Supplement
Am J Gastroenterol. 2000 May;95(5):1244-52
10811335
Scand J Gastroenterol. 1988 Dec;23(10):1237-40
3074458
Am J Clin Nutr. 1994 Jun;59(6):1362-8
8198061
Am J Clin Nutr. 1996 Sep;64(3):324-8
8780341
J Am Diet Assoc. 2002 Nov;102(11):1621-30
12449285
Eur J Gastroenterol Hepatol. 1997 Jun;9(6):553-7
9222725
Eur J Clin Nutr. 1999 Jan;53(1):1-7
10048793
Am J Clin Nutr. 1998 Feb;67(2):317-21
9459381
Aliment Pharmacol Ther. 1995 Dec;9(6):639-47
8824651
J Am Coll Nutr. 2008 Apr;27(2):356-66
18689571
Dig Dis Sci. 1998 Apr;43(4):738-45
9558028
Eur J Nutr. 2005 Oct;44(7):445-51
15696402
Int J Food Sci Nutr. 2011 Mar;62(2):164-70
21091293
Aliment Pharmacol Ther. 1988 Dec;2(6):513-9
2979274
Br J Nutr. 2012 Aug;108(3):471-81
22099384
Br Med J. 1978 May 27;1(6124):1392-4
647304
Am J Clin Nutr. 2010 Oct;92(4):723-32
20660224
Am J Clin Nutr. 1981 May;34(5):824-9
6263072
Am J Clin Nutr. 2001 Feb;73(2 Suppl):415S-420S
11157351
Eur J Clin Nutr. 2007 Oct;61(10):1189-95
17268410
Am J Gastroenterol. 2013 Sep;108(9):1541
24005363
J Nutr. 2015 Sep;145(9):2025-32
26203099
JPEN J Parenter Enteral Nutr. 1992 Nov-Dec;16(6):538-44
1337362
Nutr Today. 2015 Mar;50(2):90-97
25972619
J Nutr. 2013 Apr;143(4):473-8
23427334
Br J Nutr. 2010 Oct;104(7):1007-17
20591206
Nutr Today. 2015 Mar;50(2):82-89
25972618
Am J Clin Nutr. 1997 May;65(5):1397-402
9129468
Gastroenterology. 1995 Jun;108(6):1729-38
7768377
Gastroenterology. 1993 Apr;104(4):1007-12
8385040
Am J Clin Nutr. 1998 Sep;68(3):711-9
9734752
Regul Toxicol Pharmacol. 2000 Feb;31(1):59-67
10715225
Int J Food Sci Nutr. 2009;60 Suppl 5:96-105
19107626
Br J Nutr. 2011 Dec;106(12 ):1864-71
21736814
Eur J Clin Nutr. 1999 Sep;53(9):726-33
10509770
Gut. 1978 Jan;19(1):60-3
624508
Eur J Clin Nutr. 2006 Aug;60(8):1024-34
16482066
Br J Nutr. 1996 Aug;76(2):211-21
8813896
Br J Nutr. 1988 Nov;60(3):467-75
3219318
J Nutr. 1991 Dec;121(12):1976-83
1658279
Gastroenterology. 1995 Apr;108(4):975-82
7698613
J Nutr. 1983 Aug;113(8):1464-79
6308191
Br J Nutr. 2010 Jul;104(2):233-40
20187995
Gastroenterology. 2013 Jan;144(1):218-38
23261065
Dig Dis Sci. 1999 Apr;44(4):744-8
10219832
Food Funct. 2011 Jan;2(1):72-7
21773588
Am J Gastroenterol. 2013 May;108(5):718-27
23545709
BMJ. 1988 Nov 5;297(6657):1175-6
2849492
J Steroid Biochem Mol Biol. 2000 Apr;72(5):283-92
10822018
Ann Nutr Metab. 2010;56(2):91-8
20090313
Dis Colon Rectum. 2015 Oct;58(10):983-93
26347971
Br J Nutr. 2007 Sep;98(3):540-9
17445348
Nutr Hosp. 2012 Jan-Feb;27(1):123-9
22566311
Aliment Pharmacol Ther. 1998 May;12(5):491-7
9663731
Eur J Clin Nutr. 2004 Jul;58(7):1046-55
15220947