Effects of a diet based on inulin-rich vegetables on gut health and nutritional behavior in healthy humans

Single-group, within-subject intervention in healthy adult volunteers at Université catholique de Louvain in Louvain-la-Neuve, Belgium. Twenty-six adults were recruited; 25 completed and were analyzed, and 24 were included in gut microbiota analysis. Participants were healthy, normal-weight adults aged 18-85 years, with mean age 21.84 ± 0.39 years and mean BMI 22.29 ± 0.32.

Participants followed a 2-week diet based on inulin-type fructan rich vegetables, providing at least 9 g fructans per day and averaging 15 g/day from Jerusalem artichoke, salsify, artichoke, leek, onion, and garlic; the foods were eaten daily as meals and soup. On test days, a 16 g purified ITF load was also used for breath testing.

The ITF-rich vegetable diet was feasible and generally well tolerated, and it produced a transient increase in Bifidobacterium along with improved satiety and reduced desire for sweet and salty foods. Bifidobacterium increased 3.8-fold by sequencing and 3.0-fold by qPCR, with Bifidobacterium longum subsp. longum also increasing; these microbial changes returned toward baseline about 3 weeks after the intervention ended. Flatulence increased during the diet, but other gastrointestinal symptoms were largely unchanged, and in vivo hydrogen breath testing was not modified. The intervention also increased emotional competence and showed no significant effect on in vitro gas kinetics or SCFA production.

The study was small, short, and single-group with participants serving as their own controls, so causal inference is limited. The sample was mostly young, healthy, normal-weight, and Caucasian adults, which restricts generalizability. Several outcomes were transient or self-reported, and the intervention did not include a parallel control arm to separate diet effects from time effects.