The trillions of microbes that constitute the human gut microbiome play a crucial role in digestive health, immune response regulation, and psychological wellness. Maintaining gut microbiota is essential as metabolic diseases are associated with it. Functional food ingredients potentially improving gut health include prebiotics, probiotics, synbiotics, and postbiotics (PPSPs). While probiotics are living bacteria that provide health advantages when ingested sufficiently, prebiotics are non-digestible carbohydrates that support good gut bacteria. Synbiotics work together to improve immunity and intestinal health by combining probiotics and prebiotics. Postbiotics have also demonstrated numerous health advantages, such as bioactive molecules created during probiotic fermentation. According to a recent study, PPSPs can regulate the synthesis of metabolites, improve the integrity of the intestinal barrier, and change the gut microbiota composition to control metabolic illnesses. Additionally, the use of fecal microbiota transplantation (FMT) highlights the potential for restoring gut health through microbiota modulation, reinforcing the benefits of PPSPs in enhancing overall well-being. Research has shown that PPSPs provide several health benefits, such as improved immunological function, alleviation of symptoms associated with irritable bowel disease (IBD), decreased severity of allergies, and antibacterial and anti-inflammatory effects. Despite encouraging results, many unanswered questions remain about the scope of PPSPs’ health advantages. Extensive research is required to fully realize the potential of these functional food components in enhancing human health and well-being. Effective therapeutic and prophylactic measures require further investigation into the roles of PPSPs, specifically their immune-system-modulating, cholesterol-lowering, antioxidant, and anti-inflammatory characteristics.

Background/Objectives: Currently, Oman lacks a valid culture-specific food frequency questionnaire (FFQ) for adults. This research aimed to develop and validate a reliable (FFQ) specifically for Omani adults. The study was conducted in two phases, employing both qualitative and quantitative methods. Phase 1 was the development of the (FFQ); in this phase the Diet History Questionnaire II (DHQ II) was adapted to develop the Omani Food Frequency Questionnaire (OFFQ), translated to the Arabic language, back-translated to English, pilot tested, and then refined to be used in the reliability study. Phase 2 was the reliability study, in this phase, the OFFQ was administered twice in Arabic with the second being filled one to two weeks after the first questionnaire. Methods: A convenience sample of healthy Omani adults (n = 62) was recruited from Sultan Qaboos University (SQU) employees and students. To assess the reliability of the OFFQ both internal consistency and test–retest reliability were assessed. Internal consistency was assessed by conducting Cronbach’s α test, while test–retest reliability was assessed by comparing the median intake of food groups by calculating weighted kappa (K_W) and intraclass correlation coefficients (ICCs). Results: Weighted kappa (K_W) between the two OFFQ administrations showed fair to moderate agreement with (K_W) values ranging from 0.38 to 0.60 for questions assessing the frequency of intake. While the median (K_W) values between the two OFFQ administrations ranged from 0.26 to 0.58 for questions assessing portion size. The majority of food groups showed moderate to good test–retest reliability with median (ICCs) for food groups ranging from 0.57 to 0.80 for frequency questions and from 0.40 to 0.82 for portion questions. Conclusions: In conclusion, the newly developed OFFQ was deemed valid for the Omani dietary culture and is a reliable tool that can measure habitual dietary intake among Omani adults as evidenced by the reliability coefficients ranging from moderate to good agreement for the most food items and food groups. Future studies are warranted to assess the relative validity of the OFFQ and the inclusion of diverse demographic groups and a larger sample size.