By Scott Baltic
NEW YORK (Reuters Health) - 18/6/2019
Following a low-FODMAP diet for a limited period appears not to reduce the mean daily intake of most micronutrients in adults with irritable bowel syndrome (IBS) with diarrhea, a new study suggests.
The findings "are overall very reassuring for practitioners and patients who are using the low-FODMAP diet in their clinical practice," Dr. Shanti Eswaran of the University of Michigan in Ann Arbor told Reuters Health by email. "Given the fact that this form of dietary therapy is only intended for short-term use (4-6 weeks), the minor changes in micronutrient intake in this time period are unlikely to be detrimental."
FODMAPs are Fermentable Oligosaccharides, Disaccharides, Monosaccharides And Polyols, which can trigger symptoms in IBS patients. Several studies have shown that a diet low in FODMAPs can improve IBS symptoms, and as a consequence low-FODMAP diets are now commonly used to manage the condition.
Patients typically first restrict high-FODMAP foods and instead focus on low-FODMAP alternatives for a few weeks. One subgroup of FODMAPs at a time is then reintroduced into the patient's diet, as symptoms are monitored. In the final phase, the patient should have a personalized diet that can be safely consumed over the long term.
However, "concerns have been raised regarding the consequences of a diet low in FODMAPs, particularly surrounding nutritional adequacy and the effects on the gastrointestinal microbiota," Dr. Eswaran and colleagues note in the Journal of the Academy of Nutrition and Dietetics, online May 15.
The researchers conducted a post hoc analysis of data from a single-center randomized controlled trial that compared clinical outcomes with a low-FODMAP diet and a modified dietary intervention from the United Kingdom's National Institute for Health and Clinical Excellence (mNICE).
Data were obtained from 78 patients who completed the study: 41 in the low-FODMAP group and 37 in the mNICE group. All participants completed a three-day food record before and during the last week of four weeks on their assigned diet.
Although mean energy, nutrient, and FODMAP intake were similar between groups at baseline, by the end of the four weeks, daily mean FODMAP intake was significantly lower in the low-FODMAP arm than in the mNICE arm.
After four weeks with the low-FODMAP diet, statistically significant reductions in mean daily micronutrient intake were seen for thiamin, riboflavin, calcium, and sodium in the low-FODMAP group, but not in the mNICE group. There were also significant between-group differences.
Once adjustments were made for lower calorie intake in the low-FODMAP group, however, the only significant decrease seen was for riboflavin, while significant energy-adjusted increases were shown in niacin and vitamin B-6.
"(R)ather than nutrient density decreasing with the low-FODMAP intervention," the researchers note, "the energy-adjusted intake of vitamins A, C, E, K, niacin, and B-6; copper; and magnesium increased, indicating a more nutrient-rich diet while still removing high-FODMAP foods."
The report also pointed out that at baseline, most of the patients in each group failed to reach the Dietary Reference Intakes for vitamins C, D, and E; calcium; magnesium; and potassium.
In an email to Reuters Health, Dr. Heidi Staudacher of the Food and Mood Center at Deakin University, in Victoria, Australia, highlighted some potentially important findings from this study.
For example, fewer people could meet the recommended intakes for thiamin and iron when consuming a low-FODMAP diet, versus their pre-intervention diet. On the other hand, the low-FODMAP diet improved some aspects of dietary intake, such as reduced absolute sodium and sugar intake.
"Changes in nutrient intake in participants randomized to the standard diet were also noted, suggesting deviations in nutrient intake may occur when people with IBS follow any therapeutic diet," she added.
"The short-term low-FODMAP diet does lead to alterations in nutrient intake," concluded Dr. Staudacher, who was not involved with the study, but whether these have a detrimental impact on health is unclear.
One of the five co-authors is a consultant for Nestle S.A., Sweden. No potential conflict of interest was reported by the other authors.
The study was supported by a Michigan Nutrition Obesity Research Center Grant and a Clinical and Translational Science Award Grant, as well as by Prometheus Therapeutics and Diagnostics, San Diego.
J Acad Nutr Diet 2019.