Several natural compounds have been explored as immune-boosting, antioxidant, and anti-inflammatory dietary supplements. Amongst them, hydroxytyrosol a natural antioxidant found in olive products, and endemic medicinal plants have attracted the scientific's community and industry's interest. The safety and biological activity of a standardised supplement containing 10 mg of hydroxytyrosol synthesized using genetically modified Escherichia coli strains and equal amounts (8.33 μL) of essential oils from oregano vulgaris, sage officinalis and crithmum maritimum in an open-label, single-arm, prospective clinical study were studied. The supplement capsules were given to 12 healthy subjects, aged 26-52, once a day for 8 weeks.

The study was designed to evaluate the safety and biological activity of the supplement Antiox-Plus: one capsule/day, 15 minutes before their main meal which contained 10 mg of HT, synthesised using genetically modified Escherichia coli strains and equal amounts (8.33 μL) of essential oils from Origanum vulgare, Sage officinalis and Crithmum maritimum. The volunteers will consume the supplement for 8 weeks. A follow-up analysis will be performed one month after the end of the supplementation period (12 weeks from the initiation of the study). During this time, the participants will consume a placebo.

The volunteers are instructed to maintain their normal dietary habits. The following measurements will be taken: A) Dietary assessment at the beginning of the study (week 0), B) Body composition analysis at the beginning (week 0) and the end of the study (week 8), C) biochemical and laboratory analysis of plasma samples at week 0, 8 and 12.

The volunteers will record their food intake for 3 days (including one day of the weekend) and will fulfil a food frequency questionnaire. Analysis of their data will be done by a certified nutritionist. Nutritional assessment will be performed using the Evexis dietary software. The Tanita Dual Frequency Body Composition Monitor "Innerscan" will be employed to measure weight, muscle mass, muscle quality score, heart rate, body fat (%), physique rating, visceral fat, metabolic age, basal metabolic rate, bone mass, body water (%) and body mass index (BMI) in the morning. Physical activity will be assessed by the Greek version of the short International Physical Activity Questionnaire (IPAQ-short).

Inclusion Criteria:

• age between 25 and 65 years
• the absence of any chronic health conditions
• adequate understanding of the study

Exclusion Criteria:

• the presence of any chronic health conditions (diabetes, hypertension, dyslipidemia)
• intake of nutritional supplements over the past 60 days
• heavy smokers (≥25 cigarettes/day)
• high alcohol use (men >14 drinks/week, women >7 drinks/week)