The menopausal transition is associated with a decline in oestrogen levels, contributing to adverse metabolic changes including increased central adiposity, systemic inflammation, and insulin resistance. These changes are linked to a higher risk of developing type 2 diabetes in postmenopausal women.

Recent evidence suggests that the gut microbiota plays an important role in metabolic regulation and glucose homeostasis. Menopause-related hormonal changes may alter the composition and function of the gut microbiome, with downstream effects on insulin sensitivity. Additionally, certain gut bacteria (i.e., Bifidobacterium species) regulate circulating oestrogen via β-glucuronidase activity, highlighting a potential interaction between microbial composition and hormonal balance. Observational findings support associations between menopausal stage, gut microbiota alterations, and insulin homeostasis.

Prebiotics are non-digestible compounds that selectively stimulate beneficial gut bacteria and may improve metabolic outcomes. Modulation of the gut microbiota through prebiotic supplementation represents a promising non-pharmacological strategy to improve glucose control. Multiple studies have demonstrated that inulin (a common prebiotic) can improve glucose regulation and aid weight loss in individuals with obesity, prediabetes, or type 2 diabetes. However, to date, no randomised controlled trials have specifically investigated prebiotic supplementation in postmenopausal women with prediabetes using dynamic measures such as the Oral Glucose Tolerance Test (OGTT).

The present study aims to investigate the effect of daily consumption of an inulin-containing prebiotic gut health drink (ió everyday) on glucose control in postmenopausal women with prediabetes. The primary objective is to determine whether the intervention improves glycaemic control. Secondary objectives include exploration of changes in metabolic markers and assessment of the role of the gut microbiota in mediating these effects.

It is hypothesised that consumption of ió everyday will improve glucose control in prediabetic women who have recently undergone menopause. This hypothesis is supported by evidence demonstrating that inulin and soluble corn fibre can improve glucose regulation and support weight management in individuals with obesity, prediabetes, or type 2 diabetes, as well as findings from a previous study (Ethics Ref ID: LSC 23/383), which demonstrated that one month of ió everyday consumption significantly reduced fasting glucose, with a trend towards weight reduction and no reported adverse effects.

This is a 4-week, randomised, placebo-controlled pilot trial investigating the effects of a gut ió everyday on glucose control in postmenopausal women with prediabetes. Participants will be allocated to either an intervention or placebo group. The intervention consists of ió everyday consumed daily for 4 weeks (one sachet daily in week 1, increasing to two sachets daily in weeks 2-4, taken with meals). The placebo group will receive matched sachets without inulin but equivalent in energy content. This is an investigator-initiated, randomised, placebo-controlled pilot study.

Inclusion Criteria::

• Female, aged 45-60 years

• Post-menopausal (no menstrual period for ≥12 months)

• No serious long-term medical conditions

• Living in the UK

• Able to read English and provide electronic informed consent

• Willing and able to comply with study procedures, including dietary intervention and sample collection

• Willing to provide stool samples at specified time points

• BMI ≥25 kg/m² with one of the following:

  • Impaired glucose tolerance (7.8-11.0 mmol/L at 2-hour OGTT), or
  • Impaired fasting glucose (5.6-6.9 mmol/L), or
  • HbA1c 5.7%-6.4%

• No intentional dieting within the past month

• No >5% body weight loss in the past year

• No changes in physical activity in the past 2-4 weeks and no intention to change during the study

Exclusion Criteria:

• Significant gastrointestinal disease (e.g., inflammatory bowel disease, coeliac disease) or other major medical conditions affecting gut microbiota or study safety
• Immunocompromised status or other serious chronic illness
• Use of antibiotics within the past 2-3 months
• Regular use of probiotics or prebiotics within the past 4 weeks
• Use of medications or special diets that significantly affect gut microbiota (e.g., chronic laxatives, immunosuppressants)
• Known allergies or intolerances to components of the prebiotic formulation
• Participation in another interventional clinical trial within the past 3 months

Postmenopausal Women

In addition to participants and investigators, laboratory personnel analysing biological samples and statisticians conducting the data analysis will be blinded to group allocation. Samples and datasets will be coded to maintain masking.