Effect of an Ulva lactuca Extract on Systemic Antioxidant and Inflammatory Biomarkers in Healthy Adults: A Randomized, Double-Blind, Placebo-Controlled Trial

Background: Ulva lactuca (sea lettuce) is a green macroalgae rich in sulfated polysaccharides (ulvans), polyphenols, and pigments with documented antioxidant and anti-inflammatory activity in preclinical models. Translational human data remain limited. Methods: Twenty healthy adults (20–35 years; BMI 18.5–30 kg/m2) were enrolled in a single-center, randomized, double-blind, placebo-controlled, parallel-group trial (CTRI/2025/11/097278) and assigned 1:1 to receive 300 mg of an U. lactuca extract or matched placebo once daily for 28 days. Antioxidant biomarkers (GSH, MDA, catalase, GPx-1, thioredoxin) and inflammatory biomarkers (CRP, IL-6, IL-1β, IL-11, PPAR-γ) were measured at Day 0 and Day 28. Safety was assessed throughout. Results: Eighteen of 20 participants completed the study. Compared with placebo, U. lactuca produced significant within-group improvements at Day 28 in GSH (+4.04 ng/mL), GPx-1 (+67.8 µU/mL), and catalase (+32.4 kU/L) and reductions in MDA (−6.08 nmol/mL) and thioredoxin (−1.48 ng/mL); inflammatory markers CRP (−0.91 mg/L), IL-6 (−2.97 pg/mL), IL-11 (−4.28 ± 1.88 ng/mL) and IL-1β (−8.87 pg/mL) decreased and PPAR-γ increased. Conclusions: In this short-duration pilot trial, daily supplementation with 300 mg of an U. lactuca extract was well tolerated and modulated systemic oxidative-stress and low-grade inflammatory biomarkers in healthy adults. Larger and longer studies in populations with elevated oxidative stress are warranted.