Coenzyme Q ₁₀ is a compound that is made naturally in the body. The Q and the 10 in coenzyme Q₁₀ refer to the groups of chemicals that make up the coenzyme. Coenzyme Q₁₀ is also known by these other names:

A coenzyme helps an enzyme do its job. An enzyme is a protein that speeds up the rate at which natural chemical reactions take place in cells of the body. The body's cells use coenzyme Q₁₀ to make energy needed for the cells to grow and stay healthy. The body also uses coenzyme Q₁₀ as an antioxidant. An antioxidant is a substance that protects cells from chemicals called free radicals. Free radicals can damage DNA (deoxyribonucleic acid). Genes, which are pieces of DNA, tell the cells how to work in the body and when to grow and divide. Damage to DNA has been linked to some kinds of cancer. By protecting cells against free radicals, antioxidants help protect the body against cancer.

Coenzyme Q₁₀ is found in most body tissues. The highest amounts are found in the heart, liver, kidneys, and pancreas. The lowest amounts are found in the lungs. The amount of coenzyme Q₁₀ in tissues decreases as people get older.

Coenzyme Q₁₀ was first identified in 1957. Its chemical structure was determined in 1958. Interest in coenzyme Q₁₀ as a possible treatment for cancer began in 1961, when it was found that some cancer patients had a lower than normal amount of it in their blood. Low blood levels of coenzyme Q₁₀ have been found in patients with myeloma, lymphoma, and cancers of the breast, lung, prostate, pancreas, colon, kidney, and head and neck.

Studies suggest that coenzyme Q₁₀ may help the immune system work better. Partly because of this, coenzyme Q₁₀ is used as adjuvant therapy for cancer. Adjuvant therapy is treatment given following the primary treatment to increase the chances of a cure.

Coenzyme Q₁₀ may be useful in treating cancer because it boosts the immune system. Also, studies suggest that CoQ₁₀ analogs (drugs that are similar to CoQ₁₀) may prevent the growth of cancer cells directly. As an antioxidant, coenzyme Q₁₀ may help prevent cancer from developing.

Refer to the PDQ health professional summary on Coenzyme Q10 for more information on the theory behind the study of coenzyme Q₁₀ in the treatment of cancer.