Dose-Dependent Vitamin C Uptake and Radical Scavenging Activity in Human Skin Measured with in vivo Electron Paramagnetic Resonance Spectroscopy

Abstract

Vitamin C is a potent radical scavenger and a physiological part of the antioxidant system in human skin. The aim of this study was to measure changes in the radical-scavenging activity of human skin in vivo due to supplementation with different doses of vitamin C and at different time points. Therefore, 33 volunteers were supplemented with vitamin C or placebo for 4 weeks. The skin radical-scavenging activity was measured with electron paramagnetic resonance spectroscopy. After 4 weeks, the intake of 100 mg vitamin C/day resulted in a significant increase in the radical-scavenging activity by 22%. Intake of 180 mg/day even resulted in a significant increase of 37%. No changes were found in the placebo group. A part of the study population was additionally measured after 2 weeks: in this group radical scavenging had already reached maximal activity after 2 weeks. In conclusion, orally administered vitamin C increases the radical-scavenging activity of the skin. The effect occurs fast and is enhanced with higher doses of vitamin C.

Determination of the Antioxidant Status of the Skin by In Vivo-Electron Paramagnetic Resonance (EPR) Spectroscopy

“…The amount of supplementation corresponded to 125 mg of calcium ascorbate per day or 800 mg of Aronia melanocarpa combined with 40 mg of calcium ascorbate. The administered vitamin C doses that were ingested by the volunteers in addition to their usual diet were consistent with the standards of the US Food and Nutrition Board and the German Nutrition Society [53]. An oral supplementation for four weeks with vitamin C and Aronia melanocarpa significantly increased the radical scavenging capacity of the skin by 22% and 23%, respectively ( Figure 2).…”

“…The second vitamin C dose showed a 1.8 times higher RPF [55]. A dose-dependence of the rate constant was clearly demonstrated, and, after two weeks, the rate constant reached its maximum [53]. The EPR technology gives an insight into the reaction towards radicals.…”

“…Therefore, it can be used as a positive control in studies on the reduction of radical formation in the skin. In one of the recent studies, the radical scavenging capacity of the human skin on the inner right forearm was examined on the baseline and four weeks after supplementation in response to supplementation with moderate vitamin C doses [53][54][55]. A total number of 33 healthy volunteers were given either supplements with vitamin C, a chokeberry peel extract (Aronia melanocarpa), or a placebo for four weeks [54].…”

“…The placebo group showed no alteration in their rate constant during the entire study [54]. In addition to these results, different vitamin C doses (dose 1: 100 mg/day; dose 2: 180 mg/day) were compared for their efficiency [53]. In this context, the radical scavenging properties of the antioxidant vitamin C were examined using EPR technology after two and four weeks, respectively.…”

“…No significant increase in the carotenoid concentration was detected subsequent to supplementation with pure vitamin C and the mixed preparations after four weeks using resonance Raman spectroscopy. Long-term effects were not assessed as the period of study was too short [53][54][55].…”