Keratin and derivatives thereof, preferably S-sulfonated keratin intermediate filament protein, S-sulfonated keratin high sulfur protein, and S-sulfonated peptides provide antioxidant activity, e.g., that equal to 200-2200 .mu.mol TEAC/100 g or 100 ml, and are useful in an oral supplement to cause reduction in oxidative stress and benefits stemming therefrom, e.g., promoting skin health and to provide anti-inflammatory effect.