March 2018 E-Journal Club

March Traineeship Group PhotoGreetings,

March was busy this year since we ran a week long traineeship and a GI Weekend Warrior in between dietetic intern rotations. It was great to meet so many of our nutrition support colleagues. The picture above was our March week long traineeship participants.

Our journal club for March was outside of our usual topics, but there are so few studies of fiber in EN formulas, it was good to take a look at some of the recent data.

March Citation:

Koecher KJ, Thomas W, Slavin JL. Healthy subjects experience bowel changes on enteral diets: addition of a fiber blend attenuates stool weight and gut bacteria decreases without changes in gas. JPEN J Parenter Enteral Nutr. 2015 Mar;39(3):337-43.


This was single center, randomized, double-blind, crossover study of 20 healthy adults to compare enteral nutrition (EN) with a fiber blend (FB) compared to fiber-free (FF) EN and their effects on bowel function, fecal bacteria, and “gastrointestinal quality of life”. Subjects completed a 14 day run-in period of typical diet, then 14 days on EN formula 1, returned to a 28 day period of typical diet, then 14 days of EN formula 2. Enteral formulas were assigned in a random fashion, with an equal number of FF-FB and FB-FF sequences, stratified by gender. During the EN periods of the study, subjects were asked to orally consume the assigned formula with no other food, but were permitted to drink water, coffee, tea, or other non-caloric beverages.

Body weight, GI quality of life, transit time (radiopaque pellet capsule), 5-day stool samples, stool frequency, Bristol Stool Scale and fecal microflora analysis were monitored.

The EN formulas were 1.5 kcal/ml, and provided 67.6 gm protein/L (18% protein, 44.8% CHO, 37.2% fat). The fiber-containing formula also provided 15 gm/L of a mix of inulin, fructooligosaccharides, gum acacia and pea fiber that was a 50:50 mix of soluble:insoluble fiber.

The amount of EN formula that subjects received daily was based on their calculated energy expenditure. Formula consumption adherence was assessed via diet records.

Inclusion and Exclusion Criteria:

Inclusion criteria:

Healthy adult men and women recruited on the University of Minnesota campus.

Exclusion criteria:

Exclusion criteria included age < 18 or > 75, BMI < 23 or > 29, any self-reported disease, use of medication (except contraception and certain over the counter medications), smoking, >2 hours exercise per week, consumption of >20 g fiber/d, pregnancy or lactation, use of laxatives, use of antibiotics in the past 6 months, use of pre or probiotic supplements in the past 2 months, use of probiotic foods in the past month, participation in another clinical trial during the last 4 weeks prior to the beginning of the study, and known allergy or sensitivity to formula ingredients.

Major Results:

Twenty-four subjects were enrolled, but 4 dropped out (2 men, 2 women) within the first 2 days and the results are based on the 20 subjects who completed the study. Subjects on FB had a 38% greater mean 5-day fecal output compared with FF (P = .0321; Table 2). Compared with habitual diet, mean 5-day fecal output was reduced by 55% on FB and by 67% on FF (both P < .0001).

Mean GI transit time was approximately 1.5 times longer during formula diets compared with habitual diet (both P < .001; Table 2), but was not significantly different between the formulas (P = .2570). Stool frequency (stools/5 d) was higher on habitual diet than on formula diets (both P < .0001) and there was no difference between formulas. Fecal moisture values were 4% (wet basis) higher on FF than both habitual diet and FB (both P < .0001; Table 2), which did not differ. Mean Bristol stool scores indicated that the stools produced on FF were least formed, intermediate on FB, and most formed on habitual diet (all P < .0001).

Overall gastrointestinal quality of life scores for subjects consuming formula diets were the same between formulas (P = .8573), but lower during habitual diet (both P < .001; Table 3). Incidence of constipation and gas/bloating symptoms were not different between formulas or between either formula and habitual diet. Incidence of symptoms related to increased bowel urgency/uncontrolled stool was highest on FF, intermediate on FB, and lowest on habitual diet (all P < .02).

Author’s Conclusions:

“Significant bowel function changes occur when healthy subjects transition to an exclusive enteral diet. Subjects consuming a formula supplemented with a fiber blend, however, experience attenuated differences from habitual diet. Subjects on the FB formula had increased fecal weight, a more moderately formed stool, less negative symptoms related to bowel urgency/uncontrolled, and moderated decreases in total bacteria and bifidobacteria compared with the FF formula. In addition, there was no difference is gas and bloating symptoms between any diet suggesting that the fiber blend was well tolerated at the dose supplemented. These results support the addition of a pea fiber, FOS, inulin, and gum acacia blend to enteral products if no contraindication exists.”


The results of this study were fairly consistent with past studies of fiber-containing EN. The effect of fiber that can be added to an EN formula (allowing it to remain liquid and not overly prone to clogging feeding tubes) does not have the same effects on GI flora and function as fiber in a normal mixed diet.

It is helpful for clinicians to note that fiber containing EN does increase the amount of stool (5-day stool output), without significantly altering transit time. Fiber in EN does have a modest effect on how “formed” stool is (Bristol Stool Scale) but it is important to keep in mind that fiber-containing EN will give you 38% more stool to deal with, compared to fiber-free EN. The fiber-containing EN did improve symptoms of bowel urgency/uncontrolled stool compared to a fiber-free EN formula.

Our group discussed how the results of this study are consistent with our general experience: in patients with limited mobility, neuromuscular disorders, requiring substantial opioids, GI dysmotility disorders, or chronic constipation, we have found that fiber-containing EN tends to give you more problems (and more stool), than solutions.

The study participants were healthy adults, so increasing GI flora with prebiotics is generally considered a good thing. However, in critically ill patients, we probably do not want to increase bacterial colonies of lactic acid producing bacteria, so we tend to shy away from fiber-containing EN in the ICU. Also, in healthy “free-living” adults, issues with gas and bloating may be substantially different than in less mobile, stressed, or pain-medication requiring patients.

In those non-critically ill patients who may benefit from fiber, the fact that a mixed diet is generally superior to current fiber-containing EN formulas is worth considering, especially when we are increasingly discussing use of blenderized and “whole-food” based EN formulas. We have noted going back to the 1980’s that in the early peptide-based EN formula animal studies, that rat-chow was often superior to any “wonder formula” they could develop. It would not be at all surprising to find that “people chow” (blenderized mixed diet) may be the best thing for feeding people.

Our Take Home Message(s)

  1. EN with a fiber-blend increases total stool output without altering GI transit, stool frequency or fecal moisture compared to a fiber-free formula in healthy adults.
  2. EN with a fiber-blend results in less stool urgency and more formed stool compared to a fiber-free EN formula in healthy adults.
  3. The effects of a standard mixed diet on bowel function are not reproduced by current fiber-containing EN, even with a fiber blend.
  4. There is a need for better studies of the effects of fiber-containing EN in hospitalized, rehab and longer-term healthcare facilities.

Other News on the UVAHS GI Nutrition Website: (

Latest PG Article: Food for Thought: Importance of Nutrition in Alcoholic Hepatitis

Upcoming Programs:  Weekend Warrior in Portland, Oregon–September 29-30, 2018

Weekend Warrior in Boston, Mass.– November 10-11, 2018

Upcoming Webinars:

  • April 24: Nutrition Intervention after Whipple Procedure
  • May 30: Nutrition Management of GI Fistulas
  • June 19: Issues in Jejunal Feeding



Joe Krenitsky MS, RDN PS – Please feel free to forward on to friends and colleagues.