Chios mastic is a natural product with strong antimicrobial, anti-inflammatory and antioxidant properties, and well-established benefits for dyspeptic disorders. The aim of the present study is to investigate the effectiveness of a natural aqueous extract of Chios mastic (mastic water), a by-product of Chios mastic processing, in the management of dyspepsia. This will be a 3-month randomized double-blind controlled clinical trial in adults with dyspepsia. Participants will be blindly randomized to an intervention group, which will receive 600 mL/d of a carbonated beverage enriched with Chios mastic water (0.2%), or a control group, which will receive 600 mL/d of an identical placebo beverage with no active ingredients. Participants will be evaluated in terms of anthropometric indices, lifestyle habits, severity of dyspepsia-related gastrointestinal symptoms, quality of life, as well as biochemical markers, both pre- and post-intervention.

The term "dyspepsia" encompasses a wide range of upper gastrointestinal symptoms, including early satiety, abdominal pain, flatulence, bloating, postprandial fullness or discomfort, nausea, vomiting, and heartburn. These symptoms are common in several gastrointestinal diseases and affect up to 40% of the population worldwide. Dyspepsia leads to reduced quality of life, functionality, and productivity, and has a significant detrimental impact on healthcare systems due to repeated patient visits to healthcare professionals and unnecessary prescription and use of medications.

Several natural plant products have emerged as potential therapeutic agents, due to their high content of bioactive compounds that can inhibit the manifestation of pathophysiological processes. Chios mastic is the resin of the mastic tree (Pistacia Lentiscus var. Chia), produced exclusively in the southern part of the Greek island of Chios. References about the medical use of Chios mastic from Greek populations for the treatment of gastrointestinal disorders or as a cosmetic agent can be found in ancient texts. Nowadays, this versatile resin has been rediscovered, not only as a traditional remedy and aromatic agent, but also as a potent phytotherapeutic product with strong anti-inflammatory and anti-oxidant properties. In 2015, Chios mastic was recognized as an herbal medicinal product by the European Medicines Agency (EMA), with two therapeutic indications: mild dyspeptic disorders and skin inflammation/healing of minor wounds (EMA/HMPC/46758/2015).

Over the last years, Chios mastic has been widely used in medicinal products and food supplements, and has become the object of intense study in the fields of Nutrition and Pharmacotechnology with the aim of investigating its beneficial effects on pathological conditions mainly located in the gastrointestinal system. The few available randomized controlled clinical trials in the field have mainly investigated the effect of supplemental administration of Chios mastic in patients with inflammatory bowel diseases (Crohn's disease), irritable bowel syndrome and functional dyspepsia, highlighting its benefits in reducing the severity of gastrointestinal symptoms and improving quality of life. However, no study to date has focused on the integration of a food/beverage enriched with Chios mastic into the usual diet of individuals with gastrointestinal disorders and on investigating its potential beneficial effects on gastrointestinal health, symptoms and health-related quality of life.

Given the beneficial effect of Chios mastic on gastrointestinal health, the aim of the present study is to investigate the effect of beverages, without added sugars or artificial sweeteners and enriched with natural aqueous extract of Chios mastic (mastic water), in individuals with dyspepsia. The research hypothesis is that the incorporation of beverages enriched with mastic water into the diet of individuals with dyspepsia will lead to an improvement in the severity of gastrointestinal symptoms and associated quality of life, highlighting them as functional substitutes for conventional beverages.

The study will be a 3-month parallel, randomized (allocation ratio 1:1), controlled, double-blind clinical trial in a sample of 60 adult patients with dyspepsia. Participants will be excluded on the basis of the presence of other chronic gastrointestinal diseases, the presence of other serious comorbidities, or recent significant changes in lifestyle habits. Participants will be randomized to an intervention group (IG) or a control group (CG). The IG will be provided with 600 mL of a sparkling beverage (Mastiqua lemon lime) containing the natural mastic aqueous extract (0.2%) to be consumed daily (3 bottles of 200 mL each). The CG will be provided with the same quantity of a placebo sparkling beverage, which will be identical in appearance and organoleptic characteristics, including the characteristic Chios mastic aroma. Randomization will be performed by an investigator with no clinical involvement, while all patients and study team members will be blinded to patient allocation in study groups. All enrolled patients will be asked to maintain their usual dietary and physical activity practices and keep their standard medical treatment stable throughout the study. The study physician will systematically record potential side-effects and will be in charge of terminating the intervention if needed.

At baseline and at the end of the 3-month study, participants will be evaluated in terms of anthropometric indices (body weight, height and waist circumference), body composition, lifestyle (diet and physical activity) habits, the presence and severity of dyspepsia-related gastrointestinal symptoms and quality of life. In addition, 12-h fasting blood samples will be collected and various biochemical markers (e.g., glucose metabolism indices, lipidemic profile, liver enzymes and inflammatory markers) will be measured in serum/plasma samples both pre- and post-intervention.

Inclusion Criteria:

• Age 30-60 years old.
• Body mass index of 20-35 kg/m2.
• Presence of dyspepsia.

Exclusion Criteria:

• Presence of chronic diseases (e.g. diabetes mellitus, cancer, cardiovascular, hepatic, renal, respiratory, chronic inflammatory and psychiatric diseases).
• Presence of other chronic gastrointestinal diseases (e.g. gastroesophageal reflux, inflammatory bowel disease and celiac disease).
• Use of immunosuppressants, anti-inflammatories, antibiotics and corticosteroids.
• Use of dietary supplements or other products with Chios mastic.
• Excessive alcohol consumption (>210 g and >140 g of ethanol per week for men and women, respectively).
• Currently on a weight-loss diet or recent (within 6 months) significant change in lifestyle habits.
• Pregnancy or breast feeding (for women)

Deidentified individual participant data will be shared to investigators for the purpose of data meta-analysis, provided that the proposed use of the data has been approved by the Study Principal Investigator. Proposals should be directed to garn@hua.gr.