Does CoQ10 help your heart or your energy levels?
For people with moderate to severe heart failure, CoQ10 has the most convincing evidence base; for energy in healthy people the evidence is too thin to promise anything, but the compound is safe.
CoQ10 has its strongest evidence base in chronic heart failure. In the Q-SYMBIO trial, 420 patients with moderate to severe heart failure received 300 mg of CoQ10 per day for two years, on top of their usual medication. In the CoQ10 group, 15% experienced serious cardiac events, compared with 26% in the placebo group. Cardiovascular mortality was 9% versus 16%, and total mortality was 10% versus 18%. Those are substantial differences for a supplement. One important caveat: after 16 weeks there was still nothing to see on short-term measures such as walking distance or functional class. The benefit only became visible after two years.
Outside this trial, the evidence for heart failure is patchy. Earlier, smaller studies produced conflicting results and were too small to support firm conclusions. Q-SYMBIO remains the most robust study to date, but large independent replication studies are still lacking. That makes it difficult to place all the weight on a single trial.
For energy and athletic performance in healthy people, the picture is considerably thinner. A systematic review of thirteen studies found that, while CoQ10 is involved in cellular energy production and protects against oxidative damage, a noticeable improvement in energy levels or athletic performance in healthy people has not been demonstrated conclusively. If you are already healthy and taking CoQ10 for more energy, you are doing so without solid evidence.
In people experiencing muscle pain caused by cholesterol-lowering drugs (statins), summaries of multiple studies point to a possible benefit, but the individual studies still contradict each other too much to allow a clear recommendation. In certain rare nerve and muscle diseases of mitochondrial origin, CoQ10 appears most promising of all the non-cardiac conditions: the compound even holds orphan-drug status for this indication, but large randomised trials are also absent here.
On the safety side, the picture is clear: multiple studies confirm that CoQ10 causes few side effects at usual doses and rarely conflicts with other medications. Absorption is worth noting, however: CoQ10 is fat-soluble and has a large molecule, which means it is absorbed slowly and incompletely. Take it preferably with a fat-rich meal, and be aware that newer, solubilised formulations are better absorbed.
This answer draws on one randomised double-blind trial in 420 heart-failure patients (Q-SYMBIO), supplemented by multiple reviews and one systematic review of thirteen studies on energy performance. For heart failure the evidence base is the most concrete, but a single trial without large independent replication means the evidence for heart failure is not yet sufficiently confirmed. For energy in healthy people, statin-related muscle pain, and neurodegeneration, the evidence is thin: the individual studies contradict each other, or large randomised trials are entirely absent. The researchers themselves note that it remains uncertain exactly how CoQ10 works, because within the cell it can act as both a protector and a stressor.
Is coffee good or bad for your heart?
For most healthy adults, three to four filtered cups per day are associated with a beneficial effect on the heart and blood vessels. Pregnant women are an important exception: for them, the maximum is one to two cups per day.
Is the Mediterranean diet really good for your heart, and why?
For people with an elevated cardiovascular risk, the Mediterranean diet is the best-supported dietary choice currently available. Both large trials and dozens of population studies confirm a lower risk of heart attack and stroke.
Do omega-3 (fish oil) supplements benefit my heart?
Fish oil has a modest, proven effect on triglycerides and possibly slightly fewer heart attacks, but does not demonstrably reduce the overall risk of death. If you already have heart problems or are at high risk, it is worth discussing with your doctor.
How harmful is prolonged stress really for my heart?
Long-term stress measurably increases your risk of cardiovascular disease, particularly through work-related stress (10-40% extra risk in large population studies). The effect is real, but smaller than that of smoking or high blood pressure.
What does long-term sleep deprivation do to your heart?
Chronically sleeping too little demonstrably increases your risk of a heart attack and high blood pressure, and genetic research makes it plausible that this is a causal relationship. Seven to eight hours per night is the zone of lowest risk: make sure you consistently stay close to that target.
Is a high homocysteine level bad for my heart?
Elevated homocysteine is associated with a higher risk of cardiovascular disease, but whether you can reduce that risk by lowering homocysteine with folic acid has not been proven on the basis of these studies. Have an elevated value discussed with your general practitioner.