How Differences in the Composition of Microorganisms in the Soil Affect the Microorganisms in the Human Gut, Through the Vegetables That Grow in it: a Process Pilot Study With Healthy Participants

NCT07742319 | Not Yet Recruiting

• 1 other identifier: NL-010026
• Study Type: interventional
• Target: 10
• Locations: 1 country
• Sites: 1

Brief Summary

There are two objectives for this clinical trial. The first is to test whether, with the current logistics and study setup it is possible to perform the study well and see where there might be bottlenecks we couldn't predict. The second objective is to investigate the relation between the composition of the microorganisms in the soil, the crops that grow in that soil, and the human gut. During the study participants will drink three vegetable smoothies a day, for two periods of one week. The only difference between the two periods is whether the vegetables come from a farm with a low diversity of microorganisms in the soil or a high diversity. Participants will be asked to give blood samples and turn in fecal samples before and after each period.

Conditions

Pilot Study

Keywords

gut microbiome; microbiome; cross-over; dietary intervention; soil-plant-gut axis; metagenomics; pilot; feasibility; healthy; Smoothie intervention; randomized controlled trial; soil microbiome; stool samples

Outcome Measures

Primary Outcomes (4)

• Feasibility of logistics of the study protocol: Deliveries

  The percentage of successful deliveries to the participants in the pre-agreed time window.

  From start enrollment to the end of treatment at 4 weeks

• Feasibility of logistics of the study protocol: Preparation of the intervention product

  Using the Daily diary (Castor questionnaire), successful preparation of the intervention product is assessed.

  From the start of the treatment period until the end at 4 weeks

• Feasibility of logistics of the study protocol: Recruitment rate

  Number of recruited participants per month until the start of the study.

  From the start of recruitment until the start of the study

• Tracing back life microorganisms from the smoothie in stool samples

  Life bacteria present in the smoothies will be cultured and sequenced to then compare to feces samples of participants

  Day 1, Day 7, Day 22, and Day 28

Secondary Outcomes (5)

• Participant compliance to the study protocol

  From start enrolment until the end of treatment at the end of 4 weeks

• Shifts in gut microbiome composition

  Baseline, Day 8, Day 21, and Day 29

• Sample completeness

  From start of treatment to the end of treatment at 4 weeks

• Asses willingness of participants to create their own intervention product

  From start treatment to end of treatment at 4 weeks

• Differences in phytonutrient levels in serum

  Baseline, Day 8, Day 21, and Day 29

Study Arms (2)

Crops derived from Low followed by High diversity soil

ACTIVE COMPARATOR

Participants will be given vegetables, originating from low- or high-microbial diversity soil, to prepare smoothies with. In this arm participants start with vegetables from a low diversity soil, after a washout period of two weeks they will receive vegetables from a high diversity soil.

Other: Low diversity vegetable smoothie; Other: High diversity vegetable smoothie

Crops derived from High followed by Low diversity soil

ACTIVE COMPARATOR

Participants will be given vegetables, originating from low- or high-microbial diversity soil, to prepare smoothies with. In this arm participants start with vegetables from a high diversity soil, after a washout period of two weeks they will receive vegetables from a low diversity soil.

Other: Low diversity vegetable smoothie; Other: High diversity vegetable smoothie

Interventions

Low diversity vegetable smoothie OTHER

Vegetable smoothie prepared with crops grown in low-microbial diversity soil

Crops derived from High followed by Low diversity soil; Crops derived from Low followed by High diversity soil

High diversity vegetable smoothie OTHER

Vegetable smoothie prepared with crops grown in high-microbial diversity soil

Crops derived from High followed by Low diversity soil; Crops derived from Low followed by High diversity soil

Eligibility Criteria

• Age: 18 Years - 70 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Aged 18 to 70 years
• Written informed consent
• Inhabitant of Leiden

You may not qualify if:

• Any documented causes of chronic disease
• Suspicion of or present excessive alcohol use defined as \>2 units/day (\>14/week)
• Recent use (\<3 months) of antibiotics
• Any known food allergy or restriction, or following a vegan/vegetarian diet
• Use of possible drugs interfering microbiota or recent (\< 3 months) changes in dosages
• A psychiatric, addictive or any other disorder that compromises the participants ability to understand the study content and to give written informed consent for participation in the study

Sponsors & Collaborators

• Leiden University Medical Center: lead
• Maastricht University: collaborator

Study Sites (1)

Leids Universitair Medisch Centrum

Leiden, South Holland, 2333ZA, Netherlands

Location

Related Publications (12)

• Julious, S.A. (2005), Sample size of 12 per group rule of thumb for a pilot study. Pharmaceut. Statist., 4: 287-291. https://doi.org/10.1002/pst.185

  BACKGROUND

• Hirt H. Healthy soils for healthy plants for healthy humans: How beneficial microbes in the soil, food and gut are interconnected and how agriculture can contribute to human health. EMBO Rep. 2020 Aug 5;21(8):e51069. doi: 10.15252/embr.202051069. Epub 2020 Jul 31.

  PMID: 32734701 BACKGROUND

• Blum WEH, Zechmeister-Boltenstern S, Keiblinger KM. Does Soil Contribute to the Human Gut Microbiome? Microorganisms. 2019 Aug 23;7(9):287. doi: 10.3390/microorganisms7090287.

  PMID: 31450753 BACKGROUND

• Fierer N. Embracing the unknown: disentangling the complexities of the soil microbiome. Nat Rev Microbiol. 2017 Oct;15(10):579-590. doi: 10.1038/nrmicro.2017.87. Epub 2017 Aug 21.

  PMID: 28824177 BACKGROUND

• David LA, Maurice CF, Carmody RN, Gootenberg DB, Button JE, Wolfe BE, Ling AV, Devlin AS, Varma Y, Fischbach MA, Biddinger SB, Dutton RJ, Turnbaugh PJ. Diet rapidly and reproducibly alters the human gut microbiome. Nature. 2014 Jan 23;505(7484):559-63. doi: 10.1038/nature12820. Epub 2013 Dec 11.

  PMID: 24336217 BACKGROUND

• Leeming ER, Louca P, Gibson R, Menni C, Spector TD, Le Roy CI. The complexities of the diet-microbiome relationship: advances and perspectives. Genome Med. 2021 Jan 20;13(1):10. doi: 10.1186/s13073-020-00813-7.

  PMID: 33472701 BACKGROUND

• Johnson AJ, Zheng JJ, Kang JW, Saboe A, Knights D, Zivkovic AM. A Guide to Diet-Microbiome Study Design. Front Nutr. 2020 Jun 12;7:79. doi: 10.3389/fnut.2020.00079. eCollection 2020.

  PMID: 32596250 BACKGROUND

• Sanna S, van Zuydam NR, Mahajan A, Kurilshikov A, Vich Vila A, Vosa U, Mujagic Z, Masclee AAM, Jonkers DMAE, Oosting M, Joosten LAB, Netea MG, Franke L, Zhernakova A, Fu J, Wijmenga C, McCarthy MI. Causal relationships among the gut microbiome, short-chain fatty acids and metabolic diseases. Nat Genet. 2019 Apr;51(4):600-605. doi: 10.1038/s41588-019-0350-x. Epub 2019 Feb 18.

  PMID: 30778224 BACKGROUND

• Albenberg LG, Wu GD. Diet and the intestinal microbiome: associations, functions, and implications for health and disease. Gastroenterology. 2014 May;146(6):1564-72. doi: 10.1053/j.gastro.2014.01.058. Epub 2014 Feb 4.

  PMID: 24503132 BACKGROUND

• Henao-Mejia J, Elinav E, Jin C, Hao L, Mehal WZ, Strowig T, Thaiss CA, Kau AL, Eisenbarth SC, Jurczak MJ, Camporez JP, Shulman GI, Gordon JI, Hoffman HM, Flavell RA. Inflammasome-mediated dysbiosis regulates progression of NAFLD and obesity. Nature. 2012 Feb 1;482(7384):179-85. doi: 10.1038/nature10809.

  PMID: 22297845 BACKGROUND

• Turnbaugh PJ, Backhed F, Fulton L, Gordon JI. Diet-induced obesity is linked to marked but reversible alterations in the mouse distal gut microbiome. Cell Host Microbe. 2008 Apr 17;3(4):213-23. doi: 10.1016/j.chom.2008.02.015.

  PMID: 18407065 BACKGROUND

• Clemente JC, Ursell LK, Parfrey LW, Knight R. The impact of the gut microbiota on human health: an integrative view. Cell. 2012 Mar 16;148(6):1258-70. doi: 10.1016/j.cell.2012.01.035.

  PMID: 22424233 BACKGROUND

Central Study Contacts

Jeroen Maljaars, MD, PhD

CONTACT

+31 71 526 3575; P.W.J.Maljaars@lumc.nl

Maarten Tushuizen, MD, PhD

CONTACT

+31 71 526 9111; M.E.Tushuizen@lumc.nl

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: TRIPLE
• Who Masked: PARTICIPANT, CARE PROVIDER, INVESTIGATOR
• Purpose: PREVENTION
• Intervention Model: CROSSOVER
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: gastroenterologist

Study Record Dates

• First Submitted: July 16, 2026
• First Posted: August 3, 2026
• Study Start: August 1, 2026
• Primary Completion (Estimated): September 1, 2026
• Study Completion (Estimated): September 1, 2026
• Last Updated: August 3, 2026

Record last verified: 2026-07

Data Sharing

• IPD Sharing: Will share
• Shared Documents: STUDY PROTOCOL, ANALYTIC CODE
• Time Frame: Beginning 1 month after publication with no end date

Locations

NL (1)