Quercetin, a natural flavonoid found in various fruits and vegetables, has gained attention for its potential role in managing hyperuricemia. Emerging evidence suggests that quercetin may reduce plasma uric acid levels by inhibiting xanthine oxidase, an enzyme responsible for uric acid production. Additionally, its anti-inflammatory and antioxidant properties could help mitigate the oxidative stress and inflammation associated with hyperuricemia. As a result, quercetin supplementation offers a promising avenue for therapeutic intervention in conditions like gout and other uric acid-related disorders.

In the present retrospective cross-sectional observational study, the investigators assessed the potential pharmacological effect of supplemental quercetin on the plasma uric acid levels of health adults. These participants visited nutritional clinics in Italy during the Coronavirus disease (COVID-19) pandemic for general health check-up in real-life to enhance their immune system with supplements aimed at providing additional protection against COVID-19 infection. The supplements, either quercetin or probiotic Streptococcus salivarius K12 (BLIS K12), were advised randomly to the participants for 90 days, tailored to individual needs and in the absence of any pre-defined criteria.

Inclusion Criteria:

• Healthy adults
• BMI between 18.5 and 29.9 kg/m²
• Non-smoker
• Consumtion of less than 3 units of alcohol per day

Exclusion Criteria:

• - Plasma uric acid concentrations above 7 mg/dL
• Diagnosis of endocrinological, metabolic, oncological, neurological, or bowel inflammatory disease diseases, gout, kidney stones

Healthy participants visited the nutritional clinics during the COVID-19 pandemic for general health check up to improve their immunological protection against COVID-19 infection.