Is there clinical evidence that antioxidants improve health?

LargelyNo, Marketing: Every cell on the planet is designed to deal with oxygen; combining it with carbon (CO2) &/or hydrogen (H2O), (along with other atoms) to release chemical energy used to facilitate/drive cellular actions. Oxidation (combining with oxygen/atoms on right side of periodic table) can also damage cellular structure, thus the concept, but with little accurate understanding of most of the complexities.