It is not known if an increase in fermented food intake relative to an individuals' habitual diet can lead to improvements in bloating, mood, or hunger levels, or increase energy levels (and reduce fatigue) in the general population. Acceptability of fermented foods across many different types of people and households is also unclear. Therefore, this research aims to investigate the potential effects of increasing fermented food intake on these outcomes, as well as the feasibility of this dietary change.

Background:

Fermented foods (e.g., kombucha, kimchi, sauerkraut) are living foods containing an ecosystem of bacteria and yeasts that use enzymes to process and transform food components. The process of fermentation results in an enhanced nutritional profile of these foods (including probiotics, prebiotics, and additional vitamins) which are associated with health benefits. The majority of people in the Western world consume low amounts of fermented food with live cultures; ~70% report never or rarely consuming fermented foods.

Existing research demonstrates that there are benefits to consuming fermented foods, including improvement of gut microbiome composition as well as reducing inflammation. Furthermore, fermented foods are a unique source of B vitamins that are related to energy levels. Low energy levels are a common but complex problem that affects healthy individuals as well as those with chronic health conditions. Whilst the underlying causes of low energy are unclear, they are a common complaint of many digestive disorders, autoimmune, chronic inflammatory conditions, and metabolic and mood disorders, all of which are associated with disturbance of the gut microbiome. Humans are unable to produce B vitamins and are reliant on diet or gut microbes to produce them. Vitamin B12 levels are ten fold greater in fermented dairy products, and can be found in fermented plant-based foods such as tempeh, making these foods a valuable source of vitamin B12, a nutrient that the human diet is commonly deficient in. Fermented foods may have the potential to improve energy, and mood, by increasing gut diversity and reducing inflammation.

Population:

This research is open to participants who are enrolled in the ZOE Health Study. Participants must be at least 18 years of age and must provide their consent in order to participate.

Design:

The Fermented Foods study will take place in an entirely remote format. This study will take part in two phases. Firstly, the participant will complete a habitual diet phase lasting one week, where the participant reports study outcomes while consuming their habitual diet (including habitual intake level of fermented foods). Secondly, the participant will complete the modification phase lasting two weeks, throughout which they are required to introduce, or increase, their habitual intake of fermented foods by three portions per day (e.g., where a participant normally consumes 1 serving per day, they will now be asked to consume 4 servings per day).

Using the ZOE Health Study app, participants will be asked to:

• Complete questionnaires to assess habitual food intake, dietary habits, health history, sleep, bowel habits and digestive health at the start and end of the study.
• Log levels of hunger, energy, mood and bloating, on a daily basis, throughout the entire study period (baseline and modification phase) using the study app.
• Log their portion intake of fermented foods, on a daily basis, throughout the entire study period.

Inclusion Criteria:

• All adults aged 18
• Able to give informed consent
• Are participants of the ZOE Health Study
• Reside in the UK.

Exclusion Criteria: Participants will be excluded if they are:

• Below the age of 18 years.
• Have an histamine intolerance.
• Have a compromised immune system.
• Have been instructed to follow a salt-restricted diet.
• Consume 8 or more portions of fermented foods on a daily basis at baseline