PQQ is a redox cofactor that exists in various foods, including fermented soybeans, green peppers, and kiwi fruit. Unlike many vitamins and nutrients, PQQ is not as widely known, yet its potential therapeutic benefits are becoming increasingly appreciated. Research has suggested that PQQ possesses antioxidant properties, which allow it to neutralize free radicals and reduce oxidative stress—an imbalance that can damage cells and lead to various health issues, including mitochondrial dysfunction.