Any dietary or drug treatment with high doses of micronutrients may override the body's own control mechanisms; therefore, micronutrient therapies may be associated with potential side effects and toxicities. High-dosed micronutrients should not be used without medical supervision.
Coenzyme Q10 supplementation has resulted in clinical improvement in some patients with various types of genetic mitochondrial disorders (‘mitochondrial encephalomyopathies’), inherited abnormalities in the function of mitochondrial energy generation (12). In those rare individuals with genetic defects in coenzyme Q10 synthesis, coenzyme Q10 supplementation has resulted in substantial improvement (13).
Congestive heart failure
In coronary artery disease, accumulation of atherosclerotic plaque in the heart (‘coronary’) arteries may prevent parts of the heart muscle from getting adequate blood supply, ultimately resulting in cardiac damage and impaired pumping ability (‘congestive heart failure’). A heart attack (‘myocardial infarction’) may also damage the heart muscle, leading to heart failure.
The finding that myocardial coenzyme Q10 levels were lower in patients with more severe versus milder heart failure led to several clinical trials of coenzyme Q10 supplementation in heart failure patients (14).
A number of small intervention trials that administered supplemental coenzyme Q10 (100–200 mg/day coenzyme Q10 for one to three months) to congestive heart failure patients, in conjunction with conventional medical therapy, have demonstrated improvements in some cardiac function measures (15, 16, 17).
However, other researchers have found that supplementing the diet with 100–200 mg/day coenzyme Q10, along with conventional medical therapy, did not significantly improve cardiac function measures or exercise performance in heart failure patients (18, 19).
A meta-analysis concluded that coenzyme Q10 improves measures of heart function in chronic heart failure (20). A randomised, double-blind, multicentre (European, Asian and Australian centres) study found in people with chronic heart failure that adjuvant treatment with coenzyme Q10 in addition to standard therapy was safe, well tolerated, and associated with a reduction in symptoms and major adverse cardiovascular events (66). Central to the loss of contractile function in heart failure is the inability of mitochondria to adequately supply the heart muscle with energy, resulting in energy deprivation in the cells and potentially cell death. Coenzyme Q10 may act in a beneficial way at multiple sites in the cascade of advancing heart failure, involving both its antioxidant activity and its role in electron transport in the mitochondrion. Coenzyme Q10 also consistently improves heart (cardiac) parameters, exercise tolerance and frequency of angina pectoris attacks.
There is promising evidence of a beneficial effect of coenzyme Q10 when given alone or in addition to standard therapies in heart failure (21, 67, 68).
Myocardial infarction and cardiac surgery
As a result of a heart attack (‘myocardial infarction’) or during cardiac surgery, the heart muscle may become oxygen-deprived (‘ischemic’). Increased generation of free oxygen radicals when the heart muscle's oxygen supply is restored (‘reperfusion’) is thought to be an important contributor to myocardial damage occurring during ‘ischemia-reperfusion’.
Another potential source of ischemia-reperfusion injury is aortic clamping during some types of cardiac surgery, such as ‘coronary artery bypass graft’ (CABG) surgery, creating new routes around obstructions in coronary arteries.
Four randomized controlled trials found that coenzyme Q10 pretreatment (60–300 mg/day for 7–14 days prior to surgery) provided some benefit in short-term outcome measures after CABG surgery (24, 25). It has been suggested that preoperative coenzyme Q10 treatment may need to commence at least one week prior to CABG surgery in order to realize any benefit (26).
The results are promising, but trials to date have included relatively few people and have only examined outcomes shortly after CABG surgery.
Insufficient blood flow to heart tissue (‘myocardial ischemia’) may also lead to chest pain (‘angina pectoris’), often experienced during exercise.
Small randomized controlled trials have examined the effects of oral coenzyme Q10 supplementation (60–600 mg/day) in addition to conventional medical therapy in patients with chronic stable angina (16). In most of the studies, coenzyme Q10 supplementation improved exercise tolerance and reduced or delayed cardiac function changes associated with myocardial ischemia compared to placebo. However, only two of the studies found significant decreases in symptom frequency.
Presently, there is only limited evidence suggesting that coenzyme Q10 supplementation would be a useful adjunct to conventional angina therapy.
The results of several small, uncontrolled studies in humans suggest that coenzyme Q10 supplementation could be beneficial in the treatment of high blood pressure (‘hypertension’) (25).
Two short-term randomized controlled trials found that the addition of 120 mg/day coenzyme Q10 to conventional medical therapy for eight weeks resulted in moderate blood pressure decreases in hypertensive individuals (27). In addition, supplementation with both coenzyme Q10 (120 mg/day) and vitamin E (300 IU/day) for 12 weeks in patients with hypertension resulted in a decrease in blood pressure (28).
A meta-analysis concluded that coenzyme Q10 is potentially of interest for hypertensive patients(29). Coenzyme Q10 reduced systolic blood pressure by up to 17 mm Hg and diastolic blood pressure by up to 10 mm Hg.
The primary action of coenzyme Q10 in clinical hypertension is the widening of blood vessels (‘vasodilation’), resulting in decreased peripheral resistance and hence lower blood pressure. Coenzyme Q10 acts most likely via its antioxidant activity, which preserves nitric oxide (NO) availability, thereby reducing the narrowing of the blood vessels (‘vasoconstriction’) (29).
A review concluded that there is promising evidence of a beneficial effect of coenzyme Q10 when given alone or in addition to standard therapies for hypertension (21).
Blood vessel dilation
Atherosclerosis is associated with impairment of the inner lining of blood vessels (‘vascular endothelium’), thereby compromising the ability of blood vessels to relax (30). Endothelium-dependent blood vessel relaxation (‘vasodilation’) is impaired in individuals with elevated blood cholesterol levels as well as in patients with heart (‘coronary’) artery disease or diabetes.
One randomized controlled trial found that coenzyme Q10 supplementation (200 mg/day) for 12 weeks improved endothelium-dependent vasodilation in diabetic patients with abnormal blood lipid profiles, although it did not restore vasodilation to levels seen in non-diabetic individuals (31).
However, in a study of 12 individuals with high blood cholesterol levels and endothelial dysfunction who were otherwise healthy, supplementation with 150 mg/day did not affect endothelium-dependent vasodilation (32).
A prospective cross-over study in 25 men with endothelial dysfunction found that coenzyme Q10 supplementation (150 mg/day) significantly improved endothelial function, similar to that of a lipid-lowering medication (33).
Large-scale studies are needed to determine whether coenzyme Q10 has therapeutic benefit in endothelium-related dysfunction of blood vessel dilation and its clinical implications.
Although blood levels of coenzyme Q10 have been found to be lower in diabetic patients than healthy controls(34), supplementation with 100 mg/day coenzyme Q10 for three months neither improved blood glucose (‘glycemic’) control nor decreased insulin requirements in type 1 diabetics compared to placebo (35). Similarly, a supplementation of 200 mg/day for six months did not improve glycemic control or blood lipid profiles in type 2 diabetics (36).
Because coenzyme Q10 supplementation did not interfere with blood glucose it has been concluded that coenzyme Q10 supplements could be used safely in diabetic patients as adjunct therapy for cardiovascular diseases.
In Parkinson's disease, decreased activity of the mitochondrial electron transport chain and increased oxidative stress in a special part of the brain (‘substantia nigra’) are thought to play a role. As part of the electron transport chain and an antioxidant, coenzyme Q10 might be beneficial in the treatment of Parkinson’s disease (37, 38).
A 16-month randomized placebo-controlled trial in 80 people with early Parkinson's disease showed that supplementation with 1200 mg/day coenzyme Q10 was associated with slower deterioration of brain function compared to placebo (39). More recently, a small placebo-controlled trial showed that oral administration of 360 mg/day coenzyme Q10 for four weeks moderately benefited Parkinson's disease patients (40).
These preliminary findings are promising, but need to be confirmed in larger clinical trials before recommending the use of coenzyme Q10 in early Parkinson's disease.
A 30-month randomized placebo-controlled trial in 347 patients with early Huntington's disease supplemented with coenzyme Q10 (600 mg/day) found that coenzyme Q10 resulted only in a non-significant (13%) decrease in the decline of behavioral and neurological symptoms (45).
Currently, there is insufficient evidence to recommend coenzyme Q10 supplements to Huntington's disease patients.
Although a few case reports and an uncontrolled trial suggest that coenzyme Q10 supplementation may be beneficial as an additional treatment to conventional therapy for breast cancer (47), the lack of controlled clinical trials makes it impossible to determine the potential effects of coenzyme Q10 supplementation in cancer patients.
Periodontal disease is an infection of the tissues (gums) that support the teeth. The widespread disease is associated with swelling, bleeding, pain, and redness of the gums. Clinical studies have reported that people with gum disease tend to have low levels of coenzyme Q10 in their gums.
In a few clinical studies involving small numbers of subjects, coenzyme Q10 supplements caused faster healing and tissue repair (48). Coenzyme Q10 is used in mouth rinse products for this condition.
Additional studies in humans are needed to evaluate the effectiveness of coenzyme Q10 when used together with traditional therapy for periodontal disease.
The role of coenzyme Q10 in mitochondrial bioenergetics suggest a possible improvement in cellular bioenergetics (69). Several randomized controlled trials examined the effects of 100–300 mg/day of coenzyme Q10 supplementation for three to eight weeks on physical performance in trained and untrained men, found inconsistent effects in exercise tolerance (e.g., increased exercise time to exhaustion) (49, 50, 51) (69, 70). Two studies actually found significantly greater improvement in measures of exercise performance after supplementation with a placebo compared to coenzyme Q10 (52, 53). In cross-country skiers CoQ10 supplementation (90 mg/day) significantly improved multiple measures of physical performance (71) Moreover, coenzyme Q10 supplementation (300 mg/day) was found to improve subjective fatigue sensation and physical performance during fatigue-inducing workload trials (72). Finally, in Japanese kendo athletes CoQ10 supplementation (300 mg/day) decreased exercise-induced muscle injury (73).
Further research should clarify the potential of coenzyme Q10 as a dietary supplement to improve exercise capacity, reduce fatigue and exercise induced damage.
Preliminary clinical studies also suggest that coenzyme Q10 may improve immune function in individuals with immune deficiencies such as AIDS (54), improve symptoms of tinnitus (55), and may be beneficial in cosmetics for healthy skin (56).
Authored by Dr Peter Engel in 2010, reviewed and revised by Dr. D. Raederstorff on 18.04.2017