The Effects of an 8-week Vegan Diet on TMAO Levels and Post-challenge Glucose Levels in Individuals With Dysglycaemia

Study Design

Interventional single group prospective trial in a patient population with identified dysglycaemia within the past 36 months defined as 2h post-challenge glucose ≥7.8 mmol/L after a standard oral glucose tolerance test or HbA1c ≥5.7% (39-46 mmol/mol). This phase clinical trial will evaluate the efficacy and underlining mechanisms of a vegan diet in promoting cardiometabolic health in those with dysglycaemia. Specifically, this trial will aim to investigate the effect of an 8-week vegan diet with follow-up at 1, 8 and 12 weeks.

Study Setting

The study will be co-ordinated within the Leicester Biomedical Research Centre (Leicester Diabetes Centre) at the Leicester General Hospital. Clinical measurement sessions will be carried out by the appointed research team. Participants will be asked to visit the study centre on five occasions.

Intervention Description and Definition

The participants will be asked to follow a diet that excludes foods hypothesised to support the syntheses of TMAO, particularly meat (any), eggs and fish (any). A number of studies suggest that dairy products may also have an effect in modulating TMAO production whereas other studies do not. Therefore, in order to avoid any potential contaminating or confounding effect, dairy products will also be avoided.

The diet employed in this study is broadly aligned to a vegan diet. The term vegan will be used to aid behaviour change and food choice. For example, an increasing array of products are now pack marked as vegan. The participants will be asked to keep their diet similar to their original and the Registered Dietitian involved in this study will plan their weekly menus accordingly.

Inclusion criteria

• Participant is willing and able to give informed consent for participation in the study
• And either:

• Overweight (White: BMI>25 - <30, South Asian/ Black and minority ethnic group <27.5) with HbA1c between HbA1c ≥5.7% and ≤ 8% (39-64 mmol/mol) identified within the last 36 months
• Obese: (White: BMI ≥30, South Asian/ Black and minority ethnic group: ≥27.5)
• Male or Female
• Aged 18 - 75 years inclusive
• Able to understand, read and speak the English language to a sufficient level to understand and take part to the study in the investigators opinion
• Have access to a phone, and willing to use it as part of the study
• Regular meat and/or fish eater (at least 3 times per week)-self reported

Exclusion criteria

Participant is unwilling or unable to give informed consent

• Non-English speakers
• HbA1c above 8% (64 mmol/mol)
• Taking any form of glucose lowering medication currently or within the last 60 days
• Current smokers
• Current use of vegan or vegetarian diet
• Recent significant weight change (10% or more) over the last 3 months
• Pregnancy/lactation
• Clinical eating disorder as detected by their GP or relevant health professional (e.g. dietitian)
• Have a terminal illness
• Current or recent (within 6 months) oral antibiotics or steroid use as their usage could impact on the gut bacteria profile
• Ongoing CVD (e.g. angina) *

• In the circumstance that an individual is not sure whether they meet the inclusion/ exclusion criteria, (i.e. they are not sure if they have ongoing CVD) this will be reviewed by a named medic on the delegation of authority log for a clinical decision to be made during baseline.