Conference Coverage

More fiber looks safe, might benefit ICU patients



MIAMI – High-fiber diets in the ICU were well tolerated and led to desirable shifts in the gut microbiome that correlated with decreased abdominal distension, according to the results of an observational cohort study.

Yichun Fu

“Higher fiber intake was associated with greater preservation of short-chain fatty acid–producing bacteria, even after we adjusted for antibiotics and acute severity of illness,” said Yichun Fu, a fourth-year medical student at Columbia University, New York, at the annual Gut Microbiota for Health World Summit.

She explained that, after 72 hours on the high-fiber diet, only 11% of patients had abdominal distension noted in their EMRs, compared with 36% of patients who received no dietary fiber (P less than .01). Fiber was not associated with bowel obstruction, high gastric residuals, enteric infections, edema, or diarrhea. She and her associates presented the findings in a poster at the meeting sponsored by the American Gastroenterological Association and the European Society for Neurogastroenterology and Motility.

Dietary fiber is a prebiotic that increases the abundance of short-chain fatty acid (SCFA)–producing bacteria in the gut. Growing evidence links these bacteria and their metabolites – such as acetate, propionate, and butyrate – to immunomodulatory benefits and suggests that they help maintain gut barrier function, glucose homeostasis, adipose tissue lipolysis, and normal blood pressure. Thus, fiber for ICU patients might make sense, but relevant dietary guidelines rarely address the topic. In practice, fiber is often withheld in the ICU because of concerns that it might cause bloating or diarrhea, Ms. Fu said.

For the study, the researchers performed 16s ribosomal RNA sequencing on baseline and 72-hour rectal swabs collected from 129 consecutive adults newly admitted to the ICU. Patients were eligible for the study regardless of whether they received nothing by mouth, enteral feeding, or food by mouth. They were grouped in tertiles based on fiber intake over 72 hours, corrected by caloric intake. The resulting groups were dubbed “no fiber” (median and interquartile range, 0 grams), “low fiber” (median, 11.2 g; IQR, 3.8-18.2 g), and “high fiber” (median, 39.3 g; IQR, 4.7-50.2 g).

Patients in these three groups had a similar relative abundance of SCFA-producing bacteria at baseline. At 72 hours, the high-fiber group had a significantly greater relative abundance of SCFA producers than the no fiber group (P = .01). Compared with no fiber, high-fiber intake also correlated with significantly increased gut bacterial diversity (P = .04) and a lower relative abundance of Enterococcus bacteria (P less than .01). None of these measures differed significantly between the no-fiber and low-fiber groups.

The groups were demographically and clinically similar at baseline, except that the high-fiber group had lower Acute Physiology and Chronic Health Evaluation IV scores (P = .02) and was less likely to receive antibiotics, mechanical ventilation, hemodialysis, or vasopressors (P less than .01). After correcting for these differences, each 10-g increase in fiber intake over 72 hours correlated with a 0.3% median increase in the relative abundance of SCFA-producing bacteria (estimated IQR, 0.10%-0.46%; P less than .01).

“Fiber may be a simple candidate therapy for ICU patients,” the researchers concluded. The team is now designing a prospective, interventional study to further test whether fiber can modify the gut microbiome to benefit ICU patients, Ms. Fu explained.

Funders included the American Gastroenterological Association, the National Institutes of Health, and the Feldstein Medical Foundation. Ms. Fu reported no competing interests.

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