Holma, R., Hongisto, S.M., Saxelin, M., & Korpela, R. (2010). Constipation is relieved more by rye bread than wheat bread or laxatives without increased adverse gastrointestinal effects. Journal of Nutrition, 140, 534–541.

To investigate the effects of rye bread and cultured buttermilk on bowel function, colon metabolism, and gastrointestinal symptoms in adults with constipation.

For three weeks before the beginning of the study, participants were instructed not to use products containing Lactobacillus rhamnosus GG (LGG). At the end of the baseline period, participants were randomized into one of five groups.

1. Rye bread: minimum of 240 g per day of whole-grain rye bread
2. LGG: 400 g per day of cultured buttermilk with LGG
3. Rye bread plus LGG: minimum 240 g per day of whole-grain rye bread and 400 g per day cultured buttermilk with LGG 
4. Laxative: laxative use as usual and maximum of 192 g per day of white wheat bread 
5. Control: maximum of 192 g per day of white wheat bread

Foods considered to have laxative effects (e.g., prunes, flax, fiber products) were only allowed for the laxative group. All participants were permitted laxative use as necessary after first contacting the principal investigator. Participants were to exclude products containing other lactic acid bacteria.

Participants collected all feces for five days during the baseline week, one day during week 1, and five days during week 3. The samples were kept frozen until taken to the study center. Sitzmarks^® Radiopaque capsules were used to determine total intestinal transit time (TITT) measurements.

• The study reported on a sample of 51 patients.
• Mean patient age was 46 years (range 22–78).
• The sample comprised 47 women and four men.
• Patients self-reported constipation and laxative use.

A metropolitan area in Helsinki, Finland

This study had a randomized, unblended, 2 x 2 factorial design (LGG given, LGG not given, rye bread given, rye bread not given).

Patients self-reported the following.

• Stool consistency (-1 = loose, 0 = normal, 1 = hard)
• Ease of defecation (-1 = easy, 0 = normal, 1 = straining)
• Rank of abdominal symptoms (i.e., abdominal pain, flatulence, borborygmi, abdominal bloating, constipation, diarrhea) (0 = no symptoms, 1 = mild, 2 = moderate, 3 = severe)

• Rye bread, compared with white wheat bread, shortened TITT by 23% (p = 0.04), increased weekly defecations by 1.4 (p = 0.014), softened feces (odds ratio [OR] = 3.98, p = 0.037), eased defecation (OR = 5.08, p = 0.018), increased fecal acetic acid by 24% (p = 0.044), increased fecal butyric acid by 63% (p < 0.001), and reduced fecal enzyme (β-glucuronidase) activity by 23% (p = 0.014).
• Rye bread, compared with laxatives, reduced TITT by 41% (p = 0.006), reduced fecal enzyme (β-glucuronidase) activity by 38% (p = 0.033), and reduced fecal pH by 0.31 units (p = 0.006).
• LGG did not significantly improve bowel function or affect colonic metabolism.
• Adverse abdominal symptoms did not significantly differ among the study groups.

In adults with constipation, bowel function and colonic metabolism may improve more with rye bread consumption than with wheat bread consumption or common laxative use without causing adverse abdominal symptoms. Cultured buttermilk with LGG did not significantly improve bowel function or affect colonic metabolism in this population.

• The sample size was small (fewer than 100). In addition, the study design was 2 x 2 factorial with a control, so five groups existed. Therefore, the already small total sample size (N = 51) was distributed into very small study groups of only 8 to 12 participants each. 
• The study was not blinded.
• The ratio of women to men was not balanced.

Rye bread consumption may be more effective in relieving constipation than wheat bread or commonly used laxatives in adults. However, the convenience sample of volunteers was small, comprised predominately men, and did not include patients with cancer. Additional study is warranted in a larger population that includes patients with cancer, as well as a balanced number of women and men.