Abstract

A randomized, placebo-controlled citizen science-based dietary intervention was conducted among 147 healthy adults to evaluate the effects of 8-week high dietary fiber (HDF) and high fermented food (HFF) diets on gut microbiota, immune function, gut transit time, well-being, and sleep quality. The HDF group significantly increased fiber intake (Δ10.3 g/1000 kcal/day) following high dietary fiber recipes with addition of dried chicory root, while the HFF group increased fermented food consumption (+6.3 portions/day), including a fermentation-derived liquid supplement. At the 21-week follow-up, modest improvements in fiber and fermented intake were sustained, compared to baseline. Microbial diversity significantly increased within the HFF and control groups, especially in HFF participants over 50 (p = 0.04). Compared to CG, HFF showed no difference in microbial diversity, whereas the HDF group showed a significant decrease. The HDF intervention enhanced butyrogenic potential by increasing Anaerostipes, Faecalibacterium, and Bifidobacterium spp., and significantly reduced gastrointestinal transit time (p = 0.01). The intake of high fiber improved and sustained sleep quality (p = 0.03). The HFF intervention significantly increased blood immune markers including CD5, CD6 and CD8A (T-cell activation), IL-18R1 (inflammatory signaling) and SIRT2, a longevity-associated deacetylase (Q < 0.05), and induced a modest shift in the gut microbiota of participants over 50 years toward a composition characteristic of younger participants. These findings highlight distinct biological pathways through which dietary fibers and fermented foods modulate host physiology. This is the first randomized controlled nutritional intervention using a citizen science approach that demonstrates the feasibility and scientific value of engaging participants in healthier food choices.

Competing Interest Statement

The authors declare the following competing interests: NP and BB are the co-founders of Anibiome, DL is employed by Horaizon, and EL is the founder of Horaizon, IR is employed by WholeFiber, WMdV is co-founder and scientific advisor of WholeFiber, FvE is the General Manager of MyMicroZoo. All other authors declare no conflict of interest.

Clinical Trial

NCT05900609

Clinical Protocols

https://pubmed.ncbi.nlm.nih.gov/39378660/

Funding Statement

This work was supported by the Dutch Digestive Health Fund (MDL Fonds), Amersfoort, the Netherlands under grant WOO 22-03. The project received financial support from the companies Ani Biome, Inc., WholeFiber Holding BV, MyMicroZoo B.V and the foundation Keep Food Simple.

Author Declarations

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

Ethical approval was obtained from the Medical Ethical Committee Brabant in March 2023. Contact address: Mw. A. Morshuis, Postbus 90151, 5000 LC Tilburg; infometcbrabant.nl; www.metcbrabant.nl The trial was prospectively registered at clinicaltrials.gov (NCT05900609) and conducted according to the declaration of Helsinki. Digital informed consent was obtained from each participant prior to inclusion in the study.

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Yes

Data availability

All data associated with this study are publicly available via Yoda, the research data management platform developed by Utrecht University, The Netherlands. The dataset can be accessed through the following DOI: https://doi.org/10.48338/VU01-K0YFNS. The dataset includes raw 16S rRNA gene sequencing data, O-link immune marker measurements, and questionnaire outcomes used to assess the distinct modulatory effects of high-fiber and fermented-food diets on gut microbiota composition, immune function, intestinal transit time, sleep quality, and overall well-being.

AbbreviationsACEabundance-based coverage estimators index;ASVsamplicon sequence variants;AUCarea under the curve;BMIbody mass index;CAZymescarbohydrate-active enzymes;CGcontrol group;CScitizen science;GEEFGut health Enhancement by Eating favorable Food;GIgastrointestinal;HDFhigh-dietary fiber;HFFhigh-fermented food;IQRinterquartile range;ITTintention to treat;LMMlinear mixed model;PPper protocol;RCTrandomized controlled trial;SCFAshort-chain fatty acids.