Vitamin C as an Antioxidant: Evaluation of Its Role in Disease Prevention

Abstract

Vitamin C in humans must be ingested for survival. Vitamin C is an electron donor, and this property accounts for all its known functions. As an electron donor, vitamin C is a potent water-soluble antioxidant in humans. Antioxidant effects of vitamin C have been demonstrated in many experiments in vitro. Human diseases such as atherosclerosis and cancer might occur in part from oxidant damage to tissues. Oxidation of lipids, proteins and DNA results in specific oxidation products that can be measured in the laboratory. While these biomarkers of oxidation have been measured in humans, such assays have not yet been validated or standardized, and the relationship of oxidant markers to human disease conditions is not clear. Epidemiological studies show that diets high in fruits and vegetables are associated with lower risk of cardiovascular disease, stroke and cancer, and with increased longevity. Whether these protective effects are directly attributable to vitamin C is not known. Intervention studies with vitamin C have shown no change in markers of oxidation or clinical benefit. Dose concentration studies of vitamin C in healthy people showed a sigmoidal relationship between oral dose and plasma and tissue vitamin C concentrations. Hence, optimal dosing is critical to intervention studies using vitamin C. Ideally, future studies of antioxidant actions of vitamin C should target selected patient groups. These groups should be known to have increased oxidative damage as assessed by a reliable biomarker or should have high morbidity and mortality due to diseases thought to be caused or exacerbated by oxidant damage.

Alimentação de suínos em terminação com dietas contendo ractopamina e extratos cítricos: desempenho e características de carcaça

“…O ácido ascórbico participa de diversos processos metabólicos, como a formação do colágeno e síntese de epinefrina, corticoesteroides e ácidos biliares (PION et al, 2004). Além de cofator enzimático, o ácido ascórbico participa dos processos de óxido-redução, aumentando a absorção de ferro e a inativação de radicais livres (PADAYATTY et al, 2003). Os benefícios da utilização terapêutica do ácido ascórbico em suínos são observados no desempenho, estresse pré-abate e na qualidade da carne (PION et al, 2004).…”

Antioxidants reveal an inverted U‐shaped dose‐response relationship between reactive oxygen species levels and the rate of aging in Caenorhabditis elegans

“…Vitamin C (VitC) is chemically an antioxidant and is used as such in disease prevention (Padayatty et al ., 2003). Although addition of VitC to the growth medium of C. elegans does not much affect the wild‐type, it does so when included in liposomes (Shibamura et al ., 2009).…”

The efficacy of vitamin C supplementation on reducing total serum cholesterol in human subjects: a review and analysis of 51 experimental trials

“…70 These findings support evidence suggesting that the hypocholesterolemic effects of vitamin C may be due to its antioxidant ability. 71,72 Vitamin C has been shown to significantly reduce lipid peroxide levels 8 and protect LDL cholesterol from oxidation, thus facilitating LDL's normal binding to membrane receptors on the liver and therefore expedite its removal from the blood by LDL-cholesterol catabolic pathways. 73 However, a couple of groups contest this finding as they observed that vitamin C did not protect plasma lipids 74 or LDL 7,75 from oxidation, and one group suggested that this is because …”