Seventeen subjects were randomly assigned in a double-blind fashion to receive a broad-based antioxidants supplement containing beta-carotene , ascorbic acid , d-alpha-tocopherol-succinate , N-acetylcysteine , riboflavin , zinc , and selenium ( antioxidant capsule group [ AO group ] ) , or a combination of alpha-ketoglutaric acid ( - KG ) and 5-hydroxymethylfurfural ( 5-HMF ; CYL concentrate supplementation group [ CS group ] ) , or placebo ( PL group ) .