• Coenzyme Q ₁₀ is a compound that is made naturally in the body. The body uses it for cell growth and to protect cells from damage that could lead to cancer (see Question 1 ¹).



• Animal studies have shown that coenzyme Q₁₀ helps the immune system work better and makes the body better able to resist certain infections and types of cancer (see Question 5 ²).



• Clinical trials have shown that coenzyme Q₁₀ helps protect the heart from the damaging side effects of doxorubicin, a drug used to treat cancer (see Question 6 ³).



• In 3 small studies of coenzyme Q₁₀ in breast cancer patients, some patients appeared to be helped by the treatment. Weaknesses in study design and reporting, however, made it unclear if benefits were caused by the coenzyme Q₁₀ or by something else (see Question 6 ³).



• Coenzyme Q₁₀ may not mix safely with other treatments. It is important that patients tell their health care providers about all therapies they are currently using or thinking of using (see Question 7 ⁴).



• Coenzyme Q₁₀ has not been carefully tested to see if it is safe and effective. Because coenzyme Q₁₀ is sold as a dietary supplement rather than a drug, it is not regulated by the US Food and Drug Administration (see Question 8 ⁵).

Glossary Terms

A laboratory experiment using animals to study the development and progression of diseases. Animal studies also test how safe and effective new treatments are before they are tested in people.

Cancer that forms in tissues of the breast, usually the ducts (tubes that carry milk to the nipple) and lobules (glands that make milk). It occurs in both men and women, although male breast cancer is rare.

A term for diseases in which abnormal cells divide without control. Cancer cells can invade nearby tissues and can spread to other parts of the body through the blood and lymph systems. There are several main types of cancer. Carcinoma is cancer that begins in the skin or in tissues that line or cover internal organs. Sarcoma is cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue. Leukemia is cancer that starts in blood-forming tissue such as the bone marrow, and causes large numbers of abnormal blood cells to be produced and enter the blood. Lymphoma and multiple myeloma are cancers that begin in the cells of the immune system. Central nervous system cancers are cancers that begin in the tissues of the brain and spinal cord.

The individual unit that makes up the tissues of the body. All living things are made up of one or more cells.

A type of research study that tests how well new medical approaches work in people. These studies test new methods of screening, prevention, diagnosis, or treatment of a disease. Also called a clinical trial.

A type of research study that tests how well new medical approaches work in people. These studies test new methods of screening, prevention, diagnosis, or treatment of a disease. Also called a clinical study.

A substance found in most tissues in the body, and in many foods. It can also be made in the laboratory. It is used by the body to produce energy for cells, and as an antioxidant. It is being studied in the treatment of cancer and in the relief of side effects caused by some cancer treatments. Also called Q10, CoQ10, vitamin Q10, and ubiquinone.

In science, a substance that is made up of more than one ingredient.

A product that is added to the diet. A dietary supplement is taken by mouth, and usually contains one or more dietary ingredient (such as vitamin, mineral, herb, amino acid, and enzyme). Also called nutritional supplement.

A drug that is used to treat many types of cancer and is being studied in the treatment of other types of cancer. Doxorubicin comes from the bacterium Streptomyces peucetius. It damages DNA (the molecules inside cells that carry genetic information) and stops cells from growing. Rapidly growing tumor cells that take up doxorubicin may die. It is a type of anthracycline antitumor antibiotic. Also called doxorubicin hydrochloride, Adriamycin PFS, Adriamycin RDF, and Rubex.

Any substance, other than food, that is used to prevent, diagnose, treat or relieve symptoms of a disease or abnormal condition. Also refers to a substance that alters mood or body function, or that can be habit-forming or addictive, especially a narcotic.

FDA. An agency in the U.S. federal government whose mission is to protect public health by making sure that food, cosmetics, and nutritional supplements are safe to use and truthfully labeled. The Food and Drug Administration also makes sure that drugs, medical devices, and equipment are safe and effective, and that blood for transfusions and transplant tissue are safe. Also called FDA.

The complex group of organs and cells that defends the body against infections and other diseases.

Invasion and multiplication of germs in the body. Infections can occur in any part of the body and can spread throughout the body. The germs may be bacteria, viruses, yeast, or fungi. They can cause a fever and other problems, depending on where the infection occurs. When the body’s natural defense system is strong, it can often fight the germs and prevent infection. Some cancer treatments can weaken the natural defense system.

A problem that occurs when treatment affects healthy tissues or organs. Some common side effects of cancer treatment are fatigue, pain, nausea, vomiting, decreased blood cell counts, hair loss, and mouth sores.

Treatment.