The present invention aims to provide a component having not only an ability to reduce oxidized coenzyme Q10 and an ability to stabilize reduced coenzyme Q10, but also nutrient, flavor, broad utility and the like, and a utilization method thereof. The present invention relates to a safe and convenient method of producing reduced coenzyme Q10, including reducing oxidized coenzyme Q10 by using, as a component derived from a naturally-occurring substance, which is safe for the body, any one or more components selected from the group consisting of an acerola extract, a tea extract, a rosemary extract, a pine bark extract and a Vaccinium vitis-idaea extract. In addition, the present invention also relates to a method of stabilizing reduced coenzyme Q10 in the co-presence of a component derived from a naturally-occurring substance, and a stabilized composition. Since the above-mentioned components derived from a naturally-occurring substance can also be expected to function as nutrients, the composition of the present invention is particularly useful as a pharmaceutical product, a supplement, a food with nutrient function claims, a food for specified health use, a nutritional supplement, a nutritional product, an animal drug, a cosmetic, a therapeutic drug and the like, which are required to show various effects.
