Abstract
BACKGROUND/OBJECTIVES: Vitamin C plays a vital role in human health, functioning as a powerful antioxidant and enzymatic cofactor. Although vitamin C bioavailability from food versus supplements has been debated, few studies have examined how intake form affects absorption and physiological markers. METHODS: This randomized, controlled, crossover trial aimed to compare the bioavailability of vitamin C consumed as a supplement, through raw fruits and vegetables, or through fruit and vegetable juice. Twelve healthy adults underwent three 1-day crossover trials, each separated by a 2-week washout. Participants consumed 101.7 mg of vitamin C via powder, raw fruits and vegetables (186.8 g), or juice (200 mL). Plasma and urinary vitamin C concentrations, urinary metabolites ((1)H NMR), and antioxidant activity (ORAC and TRAP) were assessed over 24 h. RESULTS: All interventions elevated plasma vitamin C levels, with juice yielding the highest AUC (25.3 ± 3.2 mg/dL·h). Urinary vitamin C increased in all groups. Metabolomics revealed increased urinary excretion of mannitol, glycine, taurine, dimethylglycine (DMG), and asparagine, and decreased choline and dimethylamine (DMA). Notably, urinary mannitol increased only in the morning. Choline significantly decreased after powder intake (p = 0.001), with similar trends observed in the other groups. DMG and glycine increased following raw and juiced vegetable intake. Antioxidant activity showed transient ORAC elevation post-powder but no sustained improvements. CONCLUSIONS: Vitamin C is bioavailable from all intake forms, with juice providing the most efficient absorption. Urinary metabolite changes suggest microbiota-related modulation, while antioxidant activity improvements were limited.