By Kevin Connolly, Ph.D

Ubiquinol, the reduced form of Coenzyme Q10 (CoQ10), is a recent addition to the supplement offerings of several companies, and one which has generated as much confusion as it has excitement. As a supplement, ubiquinol is fairly new. As a critical part of human metabolism, our knowledge of ubiquinol dates back nearly as far as the discovery of CoQ10. While CoQ10 is often thought of as a “static” nutrient within the context of nutrition, it is actually one which dynamically interconverts between two useful states (the oxidized “ubiquinone”, and the reduced “ubiquinol”). In this article, we will discuss ubiquinol as part of the CoQ10 “cycle”, and how this cycle has important consequences in human metabolism. Additionally, we will discuss how ubiquinol as a supplement may take advantage of this cycle to exhibit increased assimilation into the body.

What is CoQ10? One Role, Two Forms, Many Consequences Health Benefits of CoQ10 Ubiquinol as a Supplement: Additional Benefits? Summary References

What is CoQ10

Coenzyme Q10 or CoQ10 is a member of a family of important biological compounds called ubiquinones. It is a lipophilic, water-insoluble substance which participates in a variety of biochemical oxidation and reduction reactions (redox reactions). First identified in 1957 as an essential component of the energy production system in cells, CoQ10 and other members of the ubiquinone family have since been identified as critical metabolic compounds in a range of aerobic organisms. Indeed, ubiquinones are ubiquitous.

Because of its critical role in metabolism, humans have the ability to synthesize their own CoQ10 (eg. it is nutritionally non-essential), although modest amounts can be obtained through diet or as supplements. In humans, CoQ10 is found in each cell in the body, but is particularly concentrated in tissues which have large energy requirements (like the heart, liver, kidneys, and skeletal muscles), with smaller amounts in the brain, lungs, and intestines. There are also substantial amounts of CoQ10 in circulation, most often associated with lipoprotein (LDL or HDL) particles. The total CoQ10 pool in a normal adult has been estimated to be between 0.5 and 1.5 grams.

Within cells, about half of the cellular CoQ10 is found within the mitochondria (the energy-producing centers of cells), and this is where the final steps of CoQ10 synthesis occur. Extramitochondrial CoQ10 (that is, CoQ10 which is located in areas of the cell which are NOT charged with producing cellular energy) can amount to 50-60% of the total CoQ10 pool. CoQ10 is found throughout cell membranes, as well as in other cellular structures (organelles) such as nucleus, cytoplasm, and endoplasmic reticulum. Experimentation has also revealed that while the final steps of CoQ10 production occur in the mitochondria, it can be exported to other subcellular locations. Similar studies have shown that exogenous (obtained from the diet) CoQ10 incorporates not only into the mitochondria, but into the plasma (outer) membrane of cells as well as other intracellular membranes.

One Role, Two Forms, Many Consequences

In the course of participating in various oxidation and reduction reactions, CoQ10 itself is cycled between two stable states (called a “redox pair”): a fully oxidized form (“ubiquinone”), and a fully reduced form (called “ubiquinol”). CoQ10 cycles through these oxidated/reduced forms in order to achieve its metabolic goals. The CoQ10 cycle is simple: Ubiquinone picks up electrons and becomes ubiquinol. Ubiquinol release its electrons and becomes ubiquinone again. And the cycle repeats.

It would appear, therefore, that CoQ10 has a very simple function

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