(See also Overview of Medicinal Herbs and Nutraceuticals.)
Coenzyme Q10 (ubiquinone) is an enzyme that is naturally produced in the body. It participates in the energy-managing processes of cells and has an antioxidant effect. Antioxidants protect cells against damage by free radicals, which are highly chemically active by-products of normal cell activity. The levels of coenzyme Q10 seem to be lower in older people and in people with chronic diseases, such as heart problems, cancer, Parkinson disease, diabetes, human immunodeficiency virus (HIV) infection or AIDS, and muscular dystrophies. However, it is not known whether these low levels contribute to these disorders.
Rich dietary sources of coenzyme Q10 are meat, fish, and vegetable oils.
Coenzyme Q10 is being studied for use in people with heart failure and degenerative neurologic disorders, such as Parkinson disease, Huntington disease, and amyotrophic lateral sclerosis (ALS). Coenzyme Q10 may also help protect the heart from the toxic effects of certain cancer chemotherapy drugs (such as doxorubicin and daunorubicin). Although some preliminary studies suggest coenzyme Q10 may possess protective properties, more testing is needed.
Side effects are uncommon, but some people have digestive symptoms, such as abdominal pain, nausea, heartburn, diarrhea, and vomiting, and central nervous system symptoms, such as dizziness, light sensitivity, irritability, and headache. Other side effects include skin itching, rash, loss of appetite, fatigue, and flu-like symptoms. Coenzyme Q10 is not recommended for people who exercise vigorously.