Snack Foods and Their Impact on Mental Health and the Gut-brain Axis

The aim of this study is to investigate the effects of snack foods on mental health and the gut-brain axis, in adults with mild to moderate symptoms of depression and anxiety.

There is increasing evidence on the potential modulating role of healthy dietary patterns in managing symptoms of psychological distress including but not limited to depression and anxiety. Despite growing evidence, further research is required to investigate how dietary interventions may impact symptoms of depression and anxiety, as well as their mechanisms of action via the gut-brain axis. Consumption of snacks now contributes to roughly 17% and 21% of daily energy intake for men and women respectively. Therefore, snacks greatly impact nutritional intake and diet quality and can be a target of dietary manipulation for potential health benefits.

This will be the first randomised controlled trial to assess the impact of snack consumption on mental health in adults with mild to moderate symptoms of depression and anxiety. The trial will use a parallel design with a 12-week intervention. Stool and blood samples will be collected at the beginning and end of the intervention for measurement of the gut microbiota and biomarkers related to the gut-brain axis.

Eligibility Criteria:
Inclusion Criteria:

* Adults aged 18-45 years old.
* Body mass index (BMI) between 18.50-29.99kg/m2
* Score 10-29 on the patient health questionnaire anxiety and depression scale (PHQ-ADS) for mild to moderate symptoms of depression and anxiety.
* Individuals who regularly consume snacks (Classified as ≥2 per day excluding fruit, vegetable, nut and seed snacks).
* Willing to complete the 12-week intervention by adhering to snacks, complete mental health questionnaires, provide stool and blood samples, record weight and other anthropometric values and record food intake at various timepoints throughout the intervention.
* Willing to adhere to the protocol and provide informed consent.
* Fibre intake of \<30g/d
* Willing to discontinue use of pre and probiotics during the trial.

Exclusion Criteria:

* Dislike of intervention products.
* Allergy or intolerance to the intervention products
* Self-report occurrence of substance dependency or severe mental health conditions (e.g., psychosis, schizophrenia, eating disorder). Those with depressive disorders or anxiety disorders will be included in the trial providing they meet all other inclusion criteria.
* Regular consumption of experimental product as snacks and unwilling to complete a washout (no consumption for 4 weeks before baseline or during the study period).
* Changes to medication for depression or anxiety within the last 3 months (e.g., dosage, frequency, type)
* Initiation of any new medications for mental health or any form of talk therapy within the last 3 months.
* Intention to start or alter medication or therapy for mental health during the study.
* Current or previous antibiotic treatment within 4 weeks prior to the start of the study.
* Consumption of probiotics or prebiotic products within the 2 weeks prior to the start of the study
* Women who are pregnant, lactating or planning pregnancy
* Unexplained or unintentional weight loss in the past six months
* 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.