Vitamin C supplementation: a comparison of delivery methods and the ability to attenuate oxidative stress induced by ischemia-reperfusion

Abstract

Intravenous delivery of vitamin C to adult humans decreases indices of oxidative stress and in some instances improves physiological function. Oral delivery of vitamin C is more practical than intravenous but typically results in lower circulating vitamin C concentrations. The hypotheses for this study were, oral consumption of vitamin C encapsulated in liposomes would: 1) result in higher circulating vitamin C concentrations than a traditional oral supplement, and 2) better attenuate oxidative stress induced by ischemia-reperfusion. Eleven overweight/obese adults [age: 52±7 years; body mass index: 34.1±1.0 kg/m²; mean±SE] were administered a 4 g supplement of placebo, or vitamin C via different delivery methods, on four separate occasions, in a random order. The four treatments were: placebo, oral vitamin C, liposomal vitamin C, and intravenous (IV) administration of vitamin C. Concentrations of ascorbic acid, thiobarbituric acid reactive substances (TBARS), and oxidized low-density lipoproteins (Ox-LDL) were measured in venous blood at baseline, and over four hours following supplement administration. At three hours a blood pressure cuff was placed around the upper arm and inflated to 200 mmHg for 20 minutes to evoke an ischemia-reperfusion injury. Plasma ascorbic acid concentrations were significantly greater after IV vitamin C compared with all other treatments at all time points (P<0.01). At two hours, all subsequent ascorbic acid concentrations were greater after liposomal vitamin C treatment compared with oral vitamin C and placebo treatments. Plasma ascorbic acid concentrations were greater after oral vitamin C compared with placebo (P<0.01). Neither vitamin C nor ischemia-reperfusion influenced Ox-LDL. In the placebo condition, ischemia-reperfusion increased plasma TBARS concentration; all of the vitamin C treatments prevented this increase. These data suggest that liposomal encapsulation of vitamin C increases bioavailability of oral vitamin C. Additionally, the antioxidant protection provided by liposomal vitamin C is not inferior to intravenously administered vitamin C.