Last reviewed & updated: March 13, 2023
Coenzyme Q10, also called CoQ10 for short, is a popular nutritional supplement with multiple potential health benefits, including male and female reproductive health. You can purchase two different types of CoQ10: Ubiquinol and ubiquinone. What’s the difference between ubiquinol and ubiquinone? Is ubiquinol better than ubiquinone?
In short, ubiquinone is the oxidized form of CoQ10, while ubiquinol is a fully reduced form that is "ready to do the work." To understand the difference between ubiquinol and ubiquinone, CoQ10’s roles in our bodies provide the important context. CoQ10 is a vitamin-like substance (but not a vitamin) that exists in almost every cell in humans.
CoQ10 has two main functions:
- First, CoQ10 acts as an antioxidant. As an antioxidant, studies have indicated that CoQ10 may help protect our cells and their DNA from damages from free radicals, such as reactive oxygen species (ROS), which are a byproduct of normal metabolic processes. An imbalance between antioxidants like CoQ10 and ROS leads to oxidative stress.
- Second, CoQ10 is involved in the production of energy our cells need for healthy growth and maintenance. Cellular energy is generated by the mitochondria, a tiny organelle inside of our cells. Studies have suggested that CoQ10 may help the mitochondria generate energy in the form of ATP from carbohydrates and fatty acids.
Three forms of CoQ10: Ubiquinone, semiquinone and ubiquinol
In both of these processes, CoQ10 constantly shifts between three states: fully oxidized form, semi-oxidized form and fully reduced form. This movement between the three states is what gives CoQ10 its antioxidant and energy-producing power through the changes in how many electrons it can carry.
The image above shows two of the three forms of CoQ10: the fully oxidized form is called ubiquinone (left), while the fully reduced form is called ubiquinol (right). And you've guessed it: The semi-oxidized form of CoQ10 is called semiquinone.
Introduction of Ubiquinol
Until 2007, the only form of CoQ10 available as a nutritional supplement was ubiquinone, the fully oxidized form. That was when a Japanese company, Kaneka, developed a technology to create the fully reduced form of CoQ10, ubiquinol, and showed its safety and absorption into the blood.
Because ubiquinol is a much newer form of CoQ10 than ubiquinone, there are much fewer research studies on ubiquinol than on ubiquinone - including in the realm of reproductive health.
Conversion from ubiquinone to ubiquinol
When we ingest the ubiquinone form of CoQ10, whether from foods or a supplement, the body must convert ubiquinone to ubiquinol first, in order to utilize it. This is why ubiquinol is sometimes called the “active” form of CoQ10. It’s also why some scientists believe that taking a ubiquinol supplement may be a more efficient way of ensuring that our cells have enough CoQ10 that’s ready to work on ROS defenses and energy production.
Bioavailability of ubiquinol vs. ubiquinone
Another aspect of research on ubiquinol vs. ubiquinone focuses on whether ubiquinol is more bioavailable than ubiquinone. Bioavailability refers to how much of the substance we ingest can enter the blood, which is the first requirement for the substance to have its desired effects in the body.
So, do our bodies absorb ubiquinol better than ubiquinone?
A small 2014 study of 12 people compared the blood levels of CoQ10 after 4 weeks of taking 200 mg/day of ubiquinone and ubiquinol each. It found a larger increase in the serum CoQ10 level after ubiquinol supplementation than ubiquinone (4.3 µg/mL, compared to 2.5 µg/mL, with the same baseline levels).
Shortly thereafter, another group of scientists posited that the greater absorption of ubiquinol may be due to its ability to be incorporated into micelles more efficiently during the digestion process. Micelles are molecules in a water-soluble colloidal solution. Without micelles, CoQ10 is a fat-soluble compound that's difficult for our water-based body to absorb. If ubiquinol is better at forming micelles than ubiquinone, the scientists hypothesized, this could make ubiquinol more bioavailable than ubiquinone. (More on this below.)
However, results from other studies are mixed, and some scientists argue that which form of CoQ10 you take doesn’t make a significant difference in how the body absorbs the CoQ10 into the blood stream. A 2020 review reached the same conclusion, noting that there are at least five enzymatic processes in cells to convert ubiquinone to ubiquinol and vice versa, which may make both forms of CoQ10 just as efficient at raising the blood levels of total CoQ10, once ingested.
Absorption could be person-dependent
A small 2018 study found an interesting effect. While 200 mg/day of ubiquinol supplementation for 2 weeks significantly increased the serum levels of CoQ10 by 1.5-fold and the same amount and duration of ubiquinone supplementation did not result in a significant increase, the effects were variable among study subjects. Of the 10 people in the study, 6 were more responsive to ubiquinol – but 2 were more responsive to ubiquinone, suggesting that there may be a person-to-person variability, in terms of which form of CoQ10 gets absorbed more easily.
The study did not investigate why. However, if these differences are confirmed by other studies, and if genetics and other factors are involved in the different absorptions of ubiquinone and ubiquinol, this may be another area that benefits from personalized supplementation.
Delivery system may also play a role
Whether in the reduced form of ubiquinol or oxidized form of ubiquinone, CoQ10 is known to have poor bioavailability in general, due to its low solubility in water and high molecular weight. For this reason, most high-quality CoQ10 supplements come in the softgel form, where CoQ10 is suspended in oil for more efficient absorption – as opposed to crystalline form in either capsules or tablets. In the last two decades, more advanced delivery systems have been developed, with many utilizing various forms of nanotechnology.
A 2013 review of advanced delivery methods still found a generally poor absorption. In most delivery systems, less than 5% of the CoQ10 ingested was actually absorbed into the blood. Importantly, however, there were significant differences in performance between different delivery systems. While direct comparisons are difficult to make, and more investigations are needed, one delivery system – called self-emulsified drug delivery system (SEDDS) – outperformed all others by a significant margin (as much as 6 times).
What does this mean for my reproductive health?
More and more fertility doctors recommend CoQ10 supplementation to people trying to conceive, so the eggs and sperm receive antioxidant protection and there is sufficient energy to support their healthy development.
When it comes to choosing which form of CoQ10 to take, here are the takeaways:
- Both ubiquinone and ubiquinol are forms of CoQ10 and play the same roles in our body.
- Our body converts ubiquinone into ubiquinol and vice versa, helping generate energy and acting as an antioxidant for eggs and sperm in the process.
- Some studies have suggested that ubiquinol may be more absorbable than ubiquinone. If you take ubiquinol, you may need less of it than if you take ubiquinone.
- Rebecca Fett, best-selling author of "It Starts with the Egg," recommends ubiquinol in her research-driven guide to egg health.
- Whichever form of CoQ10 you take, it may be a good idea to have your levels of total CoQ10, ubiquinone and ubiquinol tested, as some people may absorb one form better than the other. Monitoring the CoQ10 levels in the blood helps you – and your doctor – ensure that your body is absorbing enough of it, and able to convert between the three forms of CoQ10.
- Opt for oil-suspended softgels and avoid tablets or capsules containing powder forms of CoQ10 for better absorption. A small number of studies suggest CoQ10 supplements that use a more advanced SEDDS may help the body absorb more.
As always, consult your healthcare provider if you are unsure which CoQ10 to take or how much you need. They can also advise you about contraindications and interactions of CoQ10. This is especially important if you are on blood thinners and other medications.
Please reach out if you have any questions – we are with you.
