Definition
Coenzyme Q10(CoQ10) also known as ubiquinone, is a powerful antioxidant discovered by researchers at the University of Wisconsin in 1957. The name of this supplement comes from the word ubiquitous, which means found everywhere. Indeed, CoQ10 is found in every cell in the body. It plays a fundamental role in the mitochondria, the parts of the cell that produce energy from food.
Japanese scientists first discovered the therapeutic properties of CoQ10 in the 1960s. Today, it is widely prescribed for heart conditions in Europe and Israel, as well as in Japan. CoQ10 appears to assist the heart during times of stress on the heart muscle, perhaps by helping it use energy more efficiently. CoQ10s best-established use is for congestive heart failure, but the evidence that it works is not entirely consistent. Ongoing research suggests that it may also be useful for other types of heart problems and for a wide variety of additional illnesses.
CoQ10 supplementation might also be of value while using certain prescription medications.
Sources
Every cell in your body needs CoQ10, but no U.S. Dietary Reference Intake (formerly known as the Recommended Dietary Allowance) has been established for this important substance because the body can manufacture CoQ10 from scratch.
Because CoQ10 is found in all animal and plant cells, we obtain small amounts of this nutrient from our diet. However, it would be hard to get a therapeutic dosage from food.
Dosages
The typical recommended dosage of CoQ10 is 30 to 300 mg daily, often divided into 2 or 3 doses. CoQ10 is fat soluble and is better absorbed when taken in an oil-based soft gel form rather than in a dry form such as tablets and capsules.
Uses
Although not all studies have been positive, the best-documented use of CoQ10 is for treating congestive heart failure. Keep in mind that it is taken along with conventional medications, not instead of them.
Weaker evidence suggests that it may be useful for cardiomyopathy and other forms of heart disease.CoQ10 may also be helpful for hypertension and for preventing the heart damage caused by certain types of cancer chemotherapy. In addition, one double-blind trial suggests that CoQ10 might be helpful for individuals with kidney failure.
Note: Individuals with severe illnesses such as heart disease, cancer and kidney failure should not use CoQ10 except under physician supervision.
CoQ10 is sometimes claimed to be an effective treatment for periodontal disease. However, the studies on which this idea is based are too flawed to be taken as meaningful.
Highly preliminary studies suggest CoQ10 might be helpful for treating amyotrophic lateral sclerosis.
CoQ10 has been tried but not found effective for the treatment of Huntington's disease.
Some evidence indicates that CoQ10 supplements may offer benefit for individuals taking medications that interfere with the body's production of CoQ10, or partially block its action. It has been suggested (but not proven) that these effects on CoQ10 may play a role in the known side effects of these treatments, and that taking CoQ10 supplements might help. The best evidence is for the cholesterol-lowering drugs in the statin family, such as lovastatin (Mevacor), simvastatin (Zocor), and pravastatin (Pravachol). For several other categories of drugs, the evidence that they interfere with CoQ10 is provocative but less than solid. These include oral diabetes drugs (especially glyburide, phenformin, and tolazamide), beta-blockers (specifically propranolol, metoprolol, and alprenolol), antipsychotic drugs in the phenothiazine family, tricyclic antidepressants, methyldopa, hydrochlorothiazide, clonidine, and hydralazine.
CoQ10 has additionally been proposed as a treatment for a wide variety of other conditions, including AIDS, angina, cancer, diabetes, male infertility, muscular dystrophy, obesity, and Parkinsons disease, but there is no solid evidence as yet that it is effective. It has also been used as a performance enhancer for athletes.
Although one double-blind study of 25 highly trained cross-country skiers found some benefit most studies evaluating this use have returned negative rather than positive results.
Scientific Evidence
Congestive Heart Failure
Most, but not all, studies tell us that CoQ10 can be helpful for people with congestive heart failure (CHF). In this serious condition, the heart muscles become weakened, resulting in poor circulation and shortness of breath.
People with CHF have significantly lower levels of CoQ10 in heart muscle cells than healthy people. This fact alone does not prove that CoQ10 supplements will help CHF; however, it prompted medical researchers to try using CoQ10 as a treatment for heart failure.
In the largest study, 641 individuals with moderate to severecongestive heart failure were monitored for 1 year. Half were given 2 mg per kilogram body weight of CoQ10 daily; the rest were given placebo. Standard therapy was continued in both groups. The participants treated with CoQ10 experienced a significant reduction in the severity of their symptoms. No such improvement was seen in the placebo group. The people who took CoQ10 also had significantly fewer hospitalizations for heart failure.
Similarly positive results were also seen in other double-blind studies involving a total of over 250 participants.
However, two recent and very well-designed double-blind studies enrolling a total of about 85 individuals with congestive heart failure failed to find any evidence of benefit The reason for this discrepancy is not clear.
Cardiomyopathy
Cardiomyopathy is the general name given to conditions in which the heart muscle gradually becomes diseased. Several small studies suggest that CoQ10 supplements are helpful for some forms of cardiomyopathy.
Hypertension
An 8-week, double-blind, placebo-controlled study of 59 men already taking medications for high blood pressure found that 120 mg daily of CoQ10 reduced blood pressure by about 9% as compared to placebo.
A 12 week, double-blind, placebo-controlled study of 83 individuals with isolated systolic hypertension (a type of high blood pressure in which only the top number is high) found that use of CoQ10 at a dose of 60mg daily improved blood pressure measurements to a similar extent.
Similar results were seen in smaller trials, most of which were not double-blind.
Safety Issues
CoQ10 appears to be extremely safe. No significant side effects have been found, even in studies that lasted a year. However, individuals with severe heart disease should not take CoQ10 (or any other supplement) except under a doctors supervision.
One study suggests that CoQ10 might reduce blood sugar levels in people with diabetes. While this could potentially be helpful for treatment of diabetes, it might present a risk as well: Diabetics using CoQ10 might inadvertently push their blood sugar levels dangerously low. However, another trial in people with diabetes found no effect on blood sugar control. The bottom line: If you have diabetes, make sure to track your blood sugar closely if you start taking CoQ10 (or, indeed, any herb or supplement).
CoQ10 chemically resembles vitamin K. Since vitamin K counters the anticoagulant effects of warfarin (Coumadin), it has been suggested that CoQ10 may have the same effect. However, a small, double-blind study found no interaction between CoQ10 and warfarin. Nonetheless, in view of warfarin’s low margin of safety, prudence indicates physician supervision before combining CoQ10 with warfarin.
The maximum safe dosages of CoQ10 for young children, pregnant or nursing women, or those with severe liver or kidney disease have not been determined.