The Mediterranean Diet and Time-Restricted Eating Dietary Interventions for Psoriasis Study

The METRED-P study will test the feasibility of implementing a Mediterranean style diet and/or time-restricted eating as dietary patterns in individuals with psoriasis. This study will address the following research questions:

1. Are participants' able to adhere to the allocated dietary intervention?
2. What is the participants' acceptability of the allocated dietary intervention?
3. What is the practicality (from a clinician's stand point) of delivering the dietary interventions?
4. When adhering to the allocated intervention, are there changes in psoriasis severity?
5. When adhering to the allocated intervention, are there changes in measures of body composition?
6. When adhering to the allocated intervention, are there changes in fasting blood measures?

Participants will attend an initial clinic visit for a fasting blood sample, psoriasis examination, body composition measurements, and will complete short multiple-choice questionnaires on the severity of their psoriasis. A Research Nutritionist will deliver the diet interventions as diet consultation sessions. These sessions are reoccurring throughout the study as virtual consultation booster sessions, which are supplemented with wellbeing check-in calls. Participants will complete short questionnaires on the severity of their psoriasis and will record their dietary intake for 4 days, before the start of the study, and on week 1, week 6, and week 12 of the study. The allocated diet should be adhered to for 12 weeks until the end of the study, where participants will return and attend a final clinic visit to repeat the measures obtained during the initial clinic visit.

Researchers will compare the feasibility of implementing a Mediterranean style diet and a Mediterranean style diet with time-restricted eating, with a UK diet with time-restricted eating.

The METRED-P study is a 12-week dietary intervention in individuals with mild-moderate psoriasis. Participants will be randomly allocated to one of three groups: a Mediterranean style diet only, a Mediterranean style diet with time-restricted eating or a UK diet with time-restricted eating.

The funding organisation (the Psoriasis Association) will support with recruitment by advertising the study on their website, on their various social media platforms, and in their monthly newsletter. Flyers will be displayed in Participant Identification Centers as well as on campus at King's College London. Social media will be used to promote the study and the study will also be advertised in the biweekly recruitment newsletter that is circulated to the staff and student population at King's College London.

Individuals responding to the study advertisements will be emailed an information sheet to evaluate if the METRED-P study is suitable for them. An eligibility video call will be arranged with the Research Nutritionist, to verify the volunteer meets the inclusion criteria, explain the information sheet and the informed consent process, and address any questions. Eligible respondents will be invited to an online video screening consultation on Microsoft Teams with the Research Nutritionist and Consultant Dermatologist to confirm their eligibility. The eligibility call and screening consultation will not be recorded and will be conducted confidentially, in a private office. Volunteers who meet the inclusion criteria will be invited to attend a screening clinic visit in the Metabolic Research Unit, 4th floor (Corridor A) at King's College London, 150 Stamford Street, SE1 9NH. The volunteer will be asked to complete the consent form and provide a fasted blood sample for a total of 13mL of blood (approximately 3.5 teaspoons) . A brief physical examination will be undertaken inclusive of weight, height, waist and hip circumference, body composition (% body fat) and clinic blood pressure. Participants will enrol in the the METRED-P study according to the inclusion and exclusion criteria and upon completing a 4-day diet diary assessment of habitual nutrient intake.

Eligible participants who passed the screening stages, will complete a hand-written 4-day diet diary and submit it by email to the Research Nutritionist prior to the initial clinic visit. Participants will arrive to the clinic at approximately 08:00AM, after a 12-hour overnight fast. A fasting blood sample will be taken intravenously for a total of 18mL of blood (approximately 4.5 teaspoons). Psoriasis severity will be assessed by the Consultant Dermatologist. Body composition and clinic blood pressure measures will be taken by the Research Nutritionist. Based on the pre-clinic 4-day diet diary, participants will receive personalised dietary guidance on their allocated dietary intervention, which should be adhered to for the duration of the study. On week 4 and week 8 of the study, virtual dietary consultation booster sessions will be arranged with the Research Nutritionist to reinforce the dietary advice and to maximise adherence with the allocated dietary interventions. Participants will also complete short multiple-choice questionnaires on the severity of their psoriasis. Wellbeing check-in calls are scheduled on week 2, week 6 and week 10 with the Research Nutritionist to ensure participant well-being and address any compliance issues. Participants will return for a clinic visit at the end of the study, to repeat the measures obtained at the initial visit and complete an exit questionnaire.

Eligibility Criteria:
Inclusion Criteria:

* adults (aged 18 years or older)
* a medical diagnosis of plaque psoriasis
* a baseline Psoriasis Area Severity Index score between 5-10 (evaluated during screening)
* a Body Mass Index between 20-40
* not on tablet or injection therapies for psoriasis, OR if on tablet or injection therapies, is 6 months stable on the same dose of tablet or injection therapies

Exclusion Criteria:

* is taking Cyclosporine or Stelara in the past 3 months
* is receiving or has received photo (light) therapies for psoriasis in the past 3 months
* is a shift worker or is involved in shift work
* is planning on international travel during the study period
* is not weight stable or has attempted to lose weight during the past 6 months
* diagnosis of a gluten, nut, peanut, fish, or shellfish allergy
* diagnosis of a gluten or dairy intolerance
* is following a restrictive diet/restricting food groups i.e vegan, vegetarian, gluten-free , or a Mediterranean style diet
* is following any intermittent fasting regimes inclusive of 5:2, alternate day fasting or modified alternate day fasting, time-restricted eating over the past 6 months
* reports a habitual eating window \< 12 h per day
* reports a baseline healthy diet (e.g. \> 5 servings of fruits and vegetables per day, 1 serving of nuts per day , 2 servings of whole grains per day, 2 servings of fish per week, \> 1 servings of nuts per day and rarely eats sweet snacks, cakes, fried foods and red meat).
* taking fish oil or other dietary supplements (except daily multivitamins providing no more than 200% of UK dietary recommended values)
* currently pregnant, currently breastfeeding or planning to become pregnant in the next 4 months
* is or has been diagnosed in the past with any of the following:

  * Anaemia
  * Asthma
  * Cancer in the last five years (except non-melanoma skin cancer)
  * Cardiovascular disease (angina, congenital heart disease, coronary artery disease, heat attack, heart failure or stoke)
  * Chronic gastrointestinal disease (Crohn's disease, ulcerative colitis, celiac disease or malabsorption diseases)
  * Chronic kidney disease
  * Dementia
  * Eating disorders (anorexia, bulimia or binge eating disorder)
  * Insulin dependent diabetes
  * Liver disease
  * Lupus
  * Multiple sclerosis
  * Rheumatoid arthritis
  * Thyroid disease
* history of bariatric surgery
* history of substance abuse or alcoholism (past history of alcohol intake \>60 units/men or 50 units/women), within the last 12 months
* taking medication likely to interfere with study outcomes e.g. steroids (except occasional use of inhalers), anti-inflammatories or immune-suppressive drugs
* taking blood pressure medication, but has not been on a stable dosage during the last 3 months
* not on a stable topical treatment regimen for psoriasis (if prescribed)
* currently participating in a pharmaceutical study for psoriasis treatments (topical, light, tablet, or injection therapies) or has participated in a pharmaceutical study \< 3 months ago
* currently participating in another diet intervention study or has participated in a diet intervention study \< 3 months ago
* unwilling to record dietary intakes using handwritten diet diaries
* not fluent in the English language
* reports to have fainted in the past during an intravenous blood test