• Coenzyme Q10 (commonly known as CoQ10) 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).
• Animal studies have shown that CoQ10 helps the immune systemwork better and makes the body better able to resist certain infections and types of cancer (see Question 5).
• Clinical trials have shown that CoQ10 helps protect the heart from the damaging side effects of doxorubicin, a drug used to treat cancer (see Question 6).
• In 3 small studies of CoQ10 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 CoQ10 or by something else (see Question 6).
• CoQ10 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).
• CoQ10 has not been carefully tested in combination with chemotherapy to see if it is safe and effective. Because CoQ10 is sold as a dietary supplement rather than a drug, it is not regulated by the US Food and Drug Administration (see Question 8).

Questions and Answers About Coenzyme Q10 (CoQ10)

1. What is CoQ10?

   CoQ10 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. CoQ10 is also known by these other names:

   • Q₁₀.
   • Vitamin Q₁₀.
   • Ubiquinone.
   • Ubidecarenone.

   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 CoQ10 to make energy needed for the cells to grow and stay healthy. The body also uses CoQ10 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.

   CoQ10 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 CoQ10 in tissues decreases as people get older.

2. What is the history of the discovery and use of CoQ10 as a complementary or alternative treatment for cancer?

   CoQ10 was first identified in 1957. Its chemical structure was determined in 1958. Interest in CoQ10 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 CoQ10 have been found in patients with myeloma, lymphoma, and cancers of the breast, lung, prostate, pancreas, colon, kidney, and head and neck.

   Research about how CoQ10 plays a key role in the way cells make energy was awarded the Nobel Prize in Chemistry in 1978.

   Studies suggest that CoQ10 may help the immune system work better. Partly because of this, CoQ10 is used as adjuvant therapy for cancer. Adjuvant therapy is treatment given following the primary treatment to lower the risk that the cancer will come back.

3. What is the theory behind the claim that CoQ10 is useful in treating cancer?

   CoQ10 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, CoQ10 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 CoQ10 in the treatment of cancer.

4. How is CoQ10 administered?

   CoQ10 is usually taken by mouth as a pill (tablet or capsule). It may also be given by injection into a vein (IV). In animal studies, CoQ10 is given by injection.

5. Have any preclinical (laboratory or animal) studies been conducted using CoQ10?

   A number of preclinical studies have been done with CoQ10. Research in a laboratory or using animals is done to find out if a drug, procedure, or treatment is likely to be useful in humans. These preclinical studies are done before any testing in humans is begun. Most laboratory studies of CoQ10 have looked at its chemical structure and how it works in the body. The following has been reported from preclinical studies of CoQ10 and cancer:

   • Animal studies found that CoQ10 boosts the immune system and helps the body fight certain infections and types of cancer.
   • CoQ10 helped to protect the hearts of study animals that were given the anticancer drug doxorubicin, an anthracycline that can cause damage to the heart muscle.
   • Laboratory and animal studies have shown that analogs (drugs that are similar to CoQ10) may stop cancer cells from growing.

6. Have any clinical trials (research studies with humans) of CoQ10 been conducted?

   There have been no well-designed clinical trials involving large numbers of patients to study the use of CoQ10 in cancer treatment. There have been some clinical trials with small numbers of people, but the way the studies were done and the amount of information reported made it unclear if benefits were caused by the CoQ10 or by something else. Most of the trials were not randomized or controlled. Randomized controlled trials give the highest level of evidence:

   • In randomized trials, volunteers are assigned randomly (by chance) to one of 2 or more groups that compare different factors related to the treatment.
   • In controlled trials, one group (called the control group) does not receive the new treatment being studied. The control group is then compared to the groups that receive the new treatment, to see if the new treatment makes a difference.

   Some research studies are published in scientific journals. Most scientific journals have experts who review research reports before they are published, to make sure that the evidence and conclusions are sound. This is called peer review. Studies published in peer-reviewed scientific journals are considered better evidence. No randomized clinical trials of CoQ10 as a treatment for cancer have been published in a peer-reviewed scientific journal.

   The following has been reported from studies of CoQ10 in humans:

   Randomized trials of CoQ10 and doxorubicin

   • A randomized trial of 20 children treated for acute lymphoblastic leukemia or non-Hodgkin lymphoma looked at whether CoQ10 would protect the heart from the damage caused by the anthracycline drug doxorubicin. The results of this trial and others have shown that CoQ10 decreases the harmful effects of doxorubicin on the heart.
   • In a larger trial, 236 patients treated for breast cancer were randomized to receive oral supplements of either 300 mg CoQ10 or placebo, each combined with 300 IU vitamin E, for 24 weeks. The study found that levels of fatigue and quality of life were not improved in patients who received CoQ10 plus vitamin E compared to patients who received the placebo.

   Studies of CoQ10 as an adjuvant therapy for breast cancer

   Small studies have been done on the use of CoQ10 after standard treatment in patients with breast cancer:

   • In a study of CoQ10 in 32 breast cancer patients, it was reported that some signs and symptoms of cancer went away in 6 patients. Details were given for only 3 of the 6 patients. The researchers also reported that all the patients in the study used less pain medicine, had improved quality of life, and did not lose weight during treatment.
   • In another study led by the same researchers, 3 breast cancer patients were given high-dose CoQ10 and followed for 3 to 5 years. The study reported that one patient had complete remission of cancer that had spread to the liver, another had remission of cancer that had spread to the chest wall, and the third had no breast cancer found after surgery.

   It is not clear, however, if the benefits reported in these studies were caused by CoQ10 therapy or something else. The studies had the following weaknesses:

   • The studies were not randomized or controlled.
   • The patients used other supplements in addition to CoQ10.
   • The patients received standard treatments before or during the CoQ10 therapy.
   • Details were not reported for all patients in the studies.

   Anecdotal reports of CoQ10

   Anecdotal reports are incomplete descriptions of the medical and treatment history of one or more patients. There have been anecdotal reports that CoQ10 has helped some cancer patients live longer, including patients with cancers of the pancreas, lung, colon, rectum, and prostate. The patients described in these reports, however, also received treatments other than CoQ10, including chemotherapy, radiation therapy, and surgery.

   In a follow-up study, two patients who had breast cancer remaining after surgery were treated with CoQ10 for 3 to 4 months. It was reported that after treatment with CoQ10, the cancer was completely gone in both patients.

7. Have any side effects or risks been reported from CoQ10?

   No serious side effects have been reported from the use of CoQ10. The most common side effects include the following:

   • Insomnia (being unable to fall sleep or stay asleep).
   • Higher than normal levels of liver enzymes.
   • Rashes.
   • Nausea.
   • Pain in the upper part of the abdomen.
   • Dizziness.
   • Feeling sensitive to light.
   • Feeling irritable.
   • Headache.
   • Heartburn.
   • Feeling very tired.

   It is important to check with health care providers to find out if CoQ10 can be safely used along with other drugs. Certain drugs, such as those that are used to lower cholesterol, blood pressure, or blood sugar levels, may decrease the effects of CoQ10. CoQ10 may change way the body uses warfarin (a drug that prevents the blood from clotting) and insulin.

   As noted in Question 1, the body uses CoQ10 as an antioxidant. Antioxidants protect cells from free radicals. Some conventional cancer therapies, such as anticancer drugs and radiation treatment, kill cancer cells in part by causing free radicals to form. Researchers are studying whether using CoQ10 along with conventional therapies has any effect, good or bad, on the way these conventional therapies work in the body.

8. Is CoQ10 approved by the US Food and Drug Administration (FDA) for use as a cancer treatment in the United States?

   CoQ10 is sold as a dietary supplement and is not approved by the FDA for use as a cancer treatment. Dietary supplements are products meant to be added to the diet. They are not drugs and are not meant to treat, prevent, or cure diseases. The manufacturer is responsible for ensuring that the product is safe and that the label claims are truthful and not misleading. The FDA does not approve dietary supplements as safe or effective before they are sold. Also, the way companies make CoQ10 is not regulated. Different batches and brands of CoQ10 supplements may be different from each other.