Effects of Plant Foods on Gastrointestinal and Cardiometabolic Health (PLANTIFUL)

A Randomised Controlled Trial Investigating the Impact of Plant Foods on Gastrointestinal and Cardiometabolic Health

The aim of this randomised controlled trial is to investigate the effects of plant foods on gastrointestinal and cardiometabolic health in healthy adults aged 30-70 years old. The main question it will answer is "what is the effect of plant foods on alpha-diversity of the gut microbiota?".

Researchers will compare two diets containing plant foods to see if they have different effects on gastrointestinal and cardiometabolic health.

Participants will be asked to replace all their meals, snacks and drinks with those provided by the study team for four weeks (6 days/week). Participants will also be asked to attend the research facility on three occasions to:

• Provide a blood sample
• Provide a urine sample
• Provide a stool sample
• Have their body composition assessed
• Have an ultrasound of their artery (arm)
• Have their blood pressure measured
• Answer questionnaires related to dietary intake, mental health, physical activity, quality of life, diet acceptability and adherence

Study Overview

• Status: Recruiting
• Conditions: Healthy Adult Volunteers; Nutrition
• Intervention / Treatment: Other: A diet containing plant foods; Other: A diet containing different plant foods

• Study Type: Interventional
• Enrollment (Estimated): 248
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United Kingdom
  • London, United Kingdom, SE1 9NH
    • Recruiting
    • King's College London
    • Contact: Clinical Trial Manager; Phone Number: +442078484552; Email: plantiful@kcl.ac.uk

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Adults aged 30-70 years of age
• Capacity to give informed consent in English
• Consume equal or less than the average UK plant food intake (number and quantity)
• Consume less than 30 g/d of fibre
• BMI 18.50-29.99 kg/m2
• Willing to complete the trial by adhering to the diet intervention, complete questionnaires, provide stool, urine and blood samples, record weight and other anthropometric values and record food intake throughout the study
• Willing and able to adhere to the protocol for the diet intervention for the whole duration of the trial (e.g., appropriate space in freezer to store meals, access to oven/microwave, no planned travelling)
• Willing to discontinue use of prebiotics and probiotics 4 weeks prior and during the intervention period
• Willing to consume animal products daily
• Medication use is stable in women receiving hormone replacement therapy (stable use for the past 3 months)

Exclusion Criteria:

• Medical history of any of the following: diabetes, major active or historic psychiatric conditions (e.g., schizophrenia), current eating disorder, alcohol abuse, active treatment for cancer in the last year, severe neurological, endocrine, renal, cardiac or pulmonary disease (or any other chronic medical condition), severe oesophagitis, gastritis or duodenitis, active diverticulitis or intestinal/colonic strictures, Coeliac disease, Crohn's disease or Ulcerative colitis, stem cell or organ transplant, gut resection surgery (excluding appendicectomy and cholecystectomy), bleeding disorder, anaphylaxis or any other major or chronic condition known to impact study outcome measures.
• A current diagnosis of IBS, as defined by the Rome IV criteria.
• Taking medications known to affect outcomes of interest, including:
• Prebiotics and probiotics 4 weeks prior to enrolment.
• Antibiotics within 4 weeks of enrolment.
• Medications known to affect blood pressure, appetite, gut motility, glucose control, or lipid levels within 4 weeks of enrolment.
• Taking any dietary supplements, apart from vitamin D or calcium supplements, 4 weeks prior to enrolment.
• Allergy or intolerance to any study food ingredients.
• Unable/dislike/unwilling to consume study foods or adhere to study protocol (e.g., not willing to drink a maximum 9 units of alcohol a week or consume animal products).
• Currently reported pregnant or lactating.
• Unwilling or unable to consume non-halal or non-kosher products.
• Estimated energy requirements of <1,500 kcal/day or >3,000 kcal/day.
• Unexplained or unintentional weight loss in the past six months.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Triple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Study Diet A; Meals, snacks and drinks that contain plant foods provided by the research team for four weeks (6 days a week).	Other: A diet containing plant foods; Study meals, snacks and drinks will be provided that contain plant foods for four weeks (6 days a week). Participants will follow guidance in self-selecting foods on one day per week.; Other Names: Study Diet A
Active Comparator: Study Diet B; Meals, snacks and drinks that contain plant foods provided by the research team for four weeks (6 days a week).	Other: A diet containing different plant foods; Study meals, snacks and drinks will be provided that contain plant foods for four weeks (6 days a week). Participants will follow guidance in self-selecting foods on one day per week.; Other Names: Study Diet B

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Alpha-diversity of the gut microbiota	The diversity of microbial taxa in faecal samples at 4 weeks assessed by calculating alpha-diversity score from 16S ribosomal RNA sequencing.	Week 4

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Absolute and change in alpha-diversity of the gut microbiota	Absolute and change in alpha-diversity as measured by the diversity of micriobial taxa in faecal samples via 16S RNA sequencing.	Baseline, Week 4
Beta-diversity of the gut microbiota	The diversity of microbial taxa in faecal samples by calculating beta-diversity via 16S ribosomal RNA sequencing.	Baseline, Week 4
Microbiota composition	Absolute and change in microbiota composition of faecal samples between baseline and Week 4 as assessed by 16S ribosomal RNA sequencing.	Baseline, Week 4
Targeted faecal and plasma metabolomics	Absolute and change in short-chain fatty acids through Liquid Chromatography - Mass Spectrometry using validated assays.	Baseline, Week 4
Targeted faecal and plasma metabolomics	Absolute and change in bile acids through Liquid Chromatography - Mass Spectrometry using validated assays.	Baseline, Week 4
Untargeted faecal metabolomics	Metabolomics analysis via 1H NMR spectroscopy.	Baseline, Week 4
Faecal water content via oven drying	Absolute and change in water content of faecal samples assessed via oven drying.	Baseline, Week 4
Stool frequency	Absolute and change in stool frequency measured via prospective 7-day stool diary	Baseline, Week 4
Stool consistency	Absolute and change in stool consistency measured by Bristol stool form scale. Scale from 1 to 7.	Baseline, Week 4
Gastrointestinal symptoms	Absolute and change in gastrointestincal symptons measured by Gastrointestinal symptoms rating scale score. Scored from 15 to 105 with lower scores indicating less severe symptoms.	Baseline, Week 4
Endothelial function	Flow mediated dilation measured via ultrasound of arm.	Baseline, Week 4
Untargeted urine and plasma metabolomics	Metabolomics measured via 1H NMR spectroscopy.	Baseline, Week 4
Targeted plasma and urine metabolomics	Metabolomics via Liquid Chromatography-Mass Spectroscopy using validated assays.	Baseline, Week 4
Blood pressure	Absolute and change in diastolic and systolic blood pressure.	Baseline, Week 4
Body composition	Absolute and change in body composition measured via biolelectrical impedance analysis (BIA).	Baseline, Week 4
Waist circumference	Absolute and change in waist circumference assessed by tape measure.	Baseline, Week 4
Dietary intake	Dietary intake measured by aggregating EPIC Norfolk food frequency questionnaire, daily food and drink diaries and food checklists.	Baseline, Week 4
Biological markers of dietary intake	Absolute and change in biomarkers of dietary intake as measured via validated assays.	Baseline, Week 4

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Health-related Quality of Life	Absolute and change in SF-36 questionnaire scores.	Baseline, Week 4
Mental Health	Absolute and change in Patient Health Questionnaire-8 and Anxiety and Depression Scale scores.	Baseline, Week 4
Diet acceptability	Acceptability of diet measured through a diet acceptability questionnaire containing multiple choice and open-ended questions.	Baseline, Week 4
Diet satisfaction	Absolute diet satisfaction measured by Food benefits assessment scale. Scored from 41 to 205 with a lower score indicating a higher diet satisfaction.	Week 4
Dietary adherence	Adherence to the intervention as measured by consumption of study meals, snacks and drinks.	Baseline, Week 4

Collaborators and Investigators

• Sponsor: King's College London
• Collaborators: University of Leeds; University of Southampton; Biotechnology and Biological Sciences Research Council

Publications and helpful links

Helpful Links

• Related Info

Study record dates

Study Major Dates

• Study Start (Estimated): April 1, 2026
• Primary Completion (Estimated): October 1, 2028
• Study Completion (Estimated): November 1, 2028

Study Registration Dates

• First Submitted: April 17, 2026
• First Submitted That Met QC Criteria: May 7, 2026
• First Posted (Actual): May 14, 2026

Study Record Updates

• Last Update Posted (Actual): May 14, 2026
• Last Update Submitted That Met QC Criteria: May 7, 2026
• Last Verified: October 1, 2025

More Information

Terms related to this study

• Other Study ID Numbers: HR-25/26-49752

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No