L-Tryptophan may boost benefits of low FODMAP diet for constipation sufferers

By Olivia Brown

- Last updated on GMT

© LaylaBird / Getty Images
© LaylaBird / Getty Images

Related tags FODMAP microbiome

A new study reports that elderly functional constipation (FC) patients receiving an L-tryptophan (TRP) supplement paired with a low FODMAP diet had significantly reduced symptom severity scores compared to individuals on the dietary intervention alone or in the control group.

While the low FODMAP dietary intervention reduced FC symptom severity scores in all patients, those supplemented with 1,000 mg of TRP showed even more pronounced reductions.

Published in the journal Nutrients​ and funded by the Medical University of Lodz and ALAP laboratories, the study also observed that the TRP metabolite of 5-HIAA was significantly increased following the intervention.

"A low FODMAP diet supplemented with L-tryptophan benefits elderly patients with functional constipation," the Polish researchers concluded. “The changes induced by that diet concern the increase in 5-HT production. The increased intake of TRP may influence its level and the activity and balance of its metabolic pathways involving the gut microbiome."

Constipation and hormone alterations

The prevalence of constipation is estimated to be around 12% to 19%​ of the global population, and another 15% to 30% over the age of 65 years are diagnosed with FC.​ The condition is diagnosed following the occurrence of two or more symptoms such as straining, lumpy or hard stools, and fewer than three spontaneous bowel movements per week in a period of three months.

While nutrition, psychological disorders and the microbiome are known to play a role​ in the occurrence of FC, its development is not fully understood. There has been increasing evidence to suggest the significance of hormonal changes in FC​, with disturbances to serotonin noted. Due to the role of TRP in the production of serotonin, the present study sought to investigate the potential effectiveness of TRP supplementation for the treatment of FC.

Study details

The researchers recruited 40 participants without any abdominal complaints and 60 patients suffering from functional constipation between the ages of 66 and 84 years. The subjects diagnosed with constipation were randomly assigned to one of two groups, which were either administered a low FODMAP diet or 1000 mg of TRP per day.

Abdominal symptoms were assessed using the abdominal pain index ranging from 1 to 7 points (S-score). Urinary concentrations of TRP and its metabolites, including 5-hydroxyindoleacetic acid (5-HIAA), kynurenine (KYN) and 3-indoxyl sulfate (3-IS) were determined using the LC-MS/MS method.

Findings indicated that initial 5-HIAA concentrations in the constipated group were lower than in the control group, while KYN and 3-IS levels were higher.

S-scores were found to positively correlate with urinary concentration of 5-HIAA, suggesting that higher levels of the metabolite were associated with more severe FC symptoms. Conversely, 3-IS was found to negative correlate with S-score.

Concentrations of 5-HIAA increased in both groups following dietary intervention and severity scores decreased, however the decrease was more significant within the TRP supplemented group.

"In summary, the pathogenesis of functional gastrointestinal diseases is complex, but 5-HT homeostasis disorders play a crucial role," the researchers wrote. "Serotonin levels in the intestinal mucosa and the blood depend on the expression of tryptophan hydroxylase and the activity of selective 5-HT reuptake transporters.

"The level of their expression is influenced by nutritional and bacterial factors. However, the main condition is consuming an appropriate amount of substrate for their synthesis, i.e., exogenous L-tryptophan. For this reason, diet is still a main element of the treatment of gastrointestinal diseases."

Source: Nutrients
doi: 10.3390/nu16071027
“A Low FODMAP Diet Supplemented with L-Tryptophan Reduces the Symptoms of Functional Constipation in Elderly Patients”
Authors: Cezary Chojnacki et al.

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