Coenzyme Q10 is an oil-soluble, vitamin-like substance present in most eukaryotic cells, primarily in the mitochondria. Enzymes are protein molecules which work as catalysts (accelerating chemical reactions); coenzymes are are non-protein compounds bound to an enzyme.

They are sometimes referred to as ‘helper molecules.’ CoQ10 aids in cellular respiration (the conversion of sugar into usable energy). It is a component of the electron transport chain and participates in aerobic respiration, generating energy in the form of ATP. Ninety-five percent of the human body’s energy is generated this way. Therefore, those organs with the highest energy requirements—such as the heart, liver and kidney—have the highest CoQ10 concentrations.

CoQ10 was first discovered by Professor Fredrick L. Crane in 1957. In 1958, its chemical structure was reported by Dr. Karl Folkers and coworkers at Merck. In 1961 Peter Mitchell proposed the electron transport chain (which includes the vital role of CoQ10) and he received a Nobel prize for the same in 1978. In 1972, Gian Paolo Littarru and Karl Folkers separately demonstrated a deficiency of CoQ10 in human heart disease. The 1980s witnessed a steep rise in the number of clinical trials due to the availability of large quantities of pure CoQ10 and methods to measure plasma and blood CoQ10 concentrations. The antioxidant role of the molecule as a free radical scavenger was widely studied by Lars Ernster. Antioxidants are molecules that can slow or stop the oxidation, or loss of electrons, of other molecules; by, for example, donating electrons to free radicals (molecules with an unpaired electron), which left unpaired can cause cellular damage.

The antioxidant nature of CoQ10 derives from its energy carrier function. As an energy carrier, the CoQ10 molecule is continually going through an oxidation-reduction cycle. As it accepts electrons, it becomes reduced. As it gives up electrons, it becomes oxidized. In its reduced form, the CoQ10 molecule holds electrons rather loosely, so this CoQ molecule will quite easily give up one or both electrons and, thus, act as an antioxidant. A daily dosage up to 3600 mg was found to be tolerated by healthy as well as unhealthy persons. However, some adverse effects, largely gastrointestinal, are reported with very high intakes. Coenzyme Q10 shares a biosynthetic pathway with cholesterol. The synthesis of an intermediary precursor of coenzyme Q10, mevalonate, is inhibited by some beta blockers, blood pressure-lowering medication, and statins, a class of cholesterol-lowering drugs.

According to the Mayo Clinic, ‘CoQ10 has been used, recommended, or studied for numerous conditions, but remains controversial as a treatment in many areas.’ Coenzyme Q10, in its reduced form as solubilized ubiquinol, is approved for use as an orphan drug (a pharmaceutical agent that has been developed specifically to treat a rare medical condition) in the treatment of Huntington’s disease and pediatric congestive heart failure; other uses are still unproven, including in the treatment of high triglycerides levels and athletic performance.

Coenzyme Q10 helps to maintain a healthy cardiovascular system. There is evidence of CoQ10 deficiency in heart failure. Recently, CoQ10 plasma concentrations have been demonstrated as an independent predictor of mortality in chronic heart failure, CoQ10 deficiency being detrimental to the long-term prognosis of chronic heart failure. CoQ10 is available as medicine in several European countries, but is in these countries also available as a food supplement. Oxidation of the circulating LDL (Low-density lipoprotein, or ‘bad cholesterol’) is thought to play a key role in the pathogenesis of atherosclerosis, which is the underlying disorder leading to heart attack and ischemic strokes. Studies in the last decade have demonstrated that the content of ubiquinol in human LDL affords protection against the oxidative modifications of LDL themselves, thus lowering their atherogenic potency.

Meat and fish are the richest source of dietary CoQ10 and levels over 50 mg/kg can be found in beef, pork and chicken heart, and chicken liver. Dairy products are much poorer sources of CoQ10 compared to animal tissues. Vegetable oils are also quite rich in CoQ10. Within vegetables, parsley, and perilla are the richest CoQ10 sources, but significant differences in their CoQ10 levels can be found in the literature. Broccoli, grape, and cauliflower are modest sources of CoQ10. Most fruit and berries represent a poor to very poor source of CoQ10, with the exception of avocado, with a relatively high CoQ10 content. Cooking by frying reduces CoQ10 content by 14–32%.

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