The article discusses the mechanistic properties and biological effects of vitamins C and E, two dietary antioxidants essential for human health. Vitamin C (ascorbic acid) is crucial for collagen synthesis and acts as a cofactor for α-ketoglutarate-dependent dioxygenases, such as prolyl hydroxylases, which play a role in collagen biosynthesis and down-regulation of hypoxia-inducible factor (HIF)-1α. Vitamin C-dependent inhibition of the HIF pathway may provide alternative approaches for controlling tumor progression, infections, and inflammation. Vitamin E (α-tocopherol) functions as a lipid-soluble antioxidant, scavenging hydroperoxy radicals in lipid membranes. Its antioxidant properties are essential for protecting erythrocyte membranes and nervous tissues. Vitamin C provides protection against oxidative stress-induced cellular damage by scavenging reactive oxygen species, while vitamin E-dependent neutralization of lipid hydroperoxyl radicals. These activities are relevant to inflammatory disorders. Vitamin C also plays a role in the function of endothelial nitric oxide synthase (eNOS) by recycling its cofactor, tetrahydrobiopterin, which is relevant to arterial elasticity and blood pressure regulation. The review emphasizes the mechanism-based effects of vitamin C and E supplementation on biomarkers and clinical outcomes from randomized, placebo-controlled trials.The article discusses the mechanistic properties and biological effects of vitamins C and E, two dietary antioxidants essential for human health. Vitamin C (ascorbic acid) is crucial for collagen synthesis and acts as a cofactor for α-ketoglutarate-dependent dioxygenases, such as prolyl hydroxylases, which play a role in collagen biosynthesis and down-regulation of hypoxia-inducible factor (HIF)-1α. Vitamin C-dependent inhibition of the HIF pathway may provide alternative approaches for controlling tumor progression, infections, and inflammation. Vitamin E (α-tocopherol) functions as a lipid-soluble antioxidant, scavenging hydroperoxy radicals in lipid membranes. Its antioxidant properties are essential for protecting erythrocyte membranes and nervous tissues. Vitamin C provides protection against oxidative stress-induced cellular damage by scavenging reactive oxygen species, while vitamin E-dependent neutralization of lipid hydroperoxyl radicals. These activities are relevant to inflammatory disorders. Vitamin C also plays a role in the function of endothelial nitric oxide synthase (eNOS) by recycling its cofactor, tetrahydrobiopterin, which is relevant to arterial elasticity and blood pressure regulation. The review emphasizes the mechanism-based effects of vitamin C and E supplementation on biomarkers and clinical outcomes from randomized, placebo-controlled trials.