What is CoQ10 and why does it matter?

Coenzyme Q10 (CoQ10) is a fat-soluble compound found in virtually every cell in the body. Its primary role is in the mitochondrial electron transport chain, where it shuttles electrons between complexes I/II and complex III during oxidative phosphorylation — the process that generates approximately 95% of cellular ATP.

Beyond energy production, CoQ10 functions as a lipid-soluble antioxidant, protecting cell membranes from oxidative damage. It is one of the few endogenously produced antioxidants that operates within the lipid bilayer, where it regenerates other antioxidants including vitamin E.

CoQ10 does not carry any EU-authorised health claims under EU Regulation 432/2012 (retained in UK law). What follows is based on clinical trial evidence, not regulatory-approved wording.

What are ubiquinone and ubiquinol?

CoQ10 exists in two interconvertible forms:

The distinction is a single chemical reaction: ubiquinone gains two electrons and two protons to become ubiquinol, and ubiquinol loses them to become ubiquinone. Your body continuously cycles between the two forms via the enzyme NADH-cytochrome b5 reductase and through the electron transport chain itself.

In healthy individuals, approximately 90–98% of circulating CoQ10 in plasma is in the ubiquinol form, regardless of which form is ingested. This is a critical point that much of the marketing material fails to mention. As reviewed by Crane (2001), the rapid interconversion between forms is fundamental to CoQ10's biological function.

Is ubiquinol really "8x more absorbable"?

This claim — or variants of it — appears frequently in supplement marketing. The reality is considerably more nuanced.

The absorption challenge for both forms of CoQ10 is the same: CoQ10 is a large, lipophilic molecule with inherently low oral bioavailability. Only a small fraction of any oral dose reaches the bloodstream, regardless of form.

Several studies have directly compared the two forms:

Langsjoen & Langsjoen (2014) published data suggesting that ubiquinol supplementation achieved higher plasma CoQ10 levels than ubiquinone in patients with advanced heart failure. However, these were patients with severely impaired redox capacity — their ability to convert ubiquinone to ubiquinol was compromised. Extrapolating these results to healthy individuals is not straightforward.

López-Lluch et al. (2019) reviewed the bioavailability evidence across multiple trials and concluded that formulation technology — how the CoQ10 is solubilised and delivered — has a greater impact on absorption than whether the starting material is ubiquinone or ubiquinol. Much of the observed difference in earlier studies was attributable to the carrier formulation (oil-based vs crystalline powder) rather than the CoQ10 form itself.

The "8x" figure, where it appears, typically compares an optimised ubiquinol softgel against a basic crystalline ubiquinone powder — not a like-for-like comparison.

Does the form you swallow determine the form your body uses?

No. This is perhaps the most important point in the entire debate.

After oral ingestion, CoQ10 — regardless of whether you take ubiquinone or ubiquinol — is absorbed through the intestinal epithelium, incorporated into chylomicrons, and transported via the lymphatic system to the liver. During intestinal absorption, a significant proportion of ubiquinol is oxidised back to ubiquinone. In the liver, ubiquinone is reduced back to ubiquinol before being packaged into lipoproteins for systemic distribution.

Mohr et al. (1992) demonstrated that ubiquinol in the blood is maintained by continuous enzymatic reduction, not by the form of the supplement taken. The body's redox machinery determines the ratio of ubiquinone to ubiquinol in circulation, not the form listed on the bottle.

This means that for healthy individuals with normal redox function, supplementing with ubiquinone results in the same circulating ubiquinol levels as supplementing with ubiquinol directly.

Does stability matter?

Yes, and this is where the practical differences become relevant.

Ubiquinone is inherently more chemically stable than ubiquinol. The reduced form (ubiquinol) is susceptible to oxidation when exposed to heat, light, and oxygen — the very conditions encountered during manufacturing, storage, and transit. Once ubiquinol oxidises, it becomes ubiquinone anyway, meaning a consumer paying a premium for a ubiquinol supplement may end up with a partially oxidised product that is functionally equivalent to a ubiquinone supplement.

Kettawan et al. (2007) examined the stability of CoQ10 formulations and found that ubiquinone maintained its integrity across a wider range of conditions. Ubiquinol formulations require additional stabilisation technologies — typically nitrogen-flushed capsules and antioxidant co-factors — to prevent degradation.

For delivery systems like microgranules, where precise dosing and long-term stability are essential, ubiquinone offers a clear practical advantage. The enteric coating protects the compound through the stomach, while the stable oxidised form ensures consistent potency throughout the shelf life of the product.

What does the clinical evidence say about efficacy?

The majority of landmark clinical trials for CoQ10 have used ubiquinone, not ubiquinol. This is partly historical — ubiquinol supplements only became commercially available in 2006 — but it means the evidence base for ubiquinone is substantially larger.

The Q-SYMBIO trial (Mortensen et al., 2014) — one of the most significant CoQ10 studies to date — used ubiquinone at 300 mg/day in patients with chronic heart failure over two years. Research from this trial indicated a significant reduction in major adverse cardiovascular events. This trial used ubiquinone, not ubiquinol.

Rosenfeldt et al. (2007) conducted a meta-analysis of CoQ10 supplementation trials and found that ubiquinone at doses of 100–300 mg/day consistently raised plasma CoQ10 levels and showed clinical benefits across multiple endpoints.

Research indicates that ubiquinone is effective at raising both plasma CoQ10 and plasma ubiquinol levels, because the body converts the ingested ubiquinone to ubiquinol as needed.

Why does PARTICULAR use ubiquinone?

PARTICULAR's CoQ10 uses ubiquinone (code PAR05) at doses of 50–100 mg, determined by your questionnaire responses. The decision was based on three factors:

Stability in the microgranule format. PARTICULAR delivers supplements as individually enteric-coated microgranules — not softgel capsules. Ubiquinone's superior chemical stability makes it the more reliable choice for this delivery system, maintaining consistent potency without requiring the additional stabilisation technologies that ubiquinol demands.

Depth of clinical evidence. The majority of clinical trials demonstrating CoQ10 efficacy have used ubiquinone. The evidence base for ubiquinol, while growing, remains smaller and often conducted by or funded by ubiquinol manufacturers.

Bioequivalence in healthy individuals. For people with normal redox function — which describes the majority of supplement consumers — the body efficiently converts ubiquinone to ubiquinol after absorption. The end result in the bloodstream is the same regardless of starting form.

CoQ10 does not carry EU-authorised health claims, so PARTICULAR does not make specific health claims for this ingredient. Its inclusion is based on the clinical trial evidence for CoQ10's role in mitochondrial function and cellular energy production.

When might ubiquinol be worth considering?

There are specific populations where the evidence tilts toward ubiquinol:

For the general population, the evidence does not support paying a premium for ubiquinol over ubiquinone.

How does CoQ10 relate to other energy-relevant nutrients?

CoQ10 works within the mitochondrial electron transport chain alongside several nutrients that carry EU-authorised claims for energy metabolism. Magnesium, iron, B vitamins, and vitamin C all contribute to normal energy-yielding metabolism under EU Regulation 432/2012.

CoQ10's role is distinct — it is the electron carrier, not a cofactor or substrate in the same sense as these vitamins and minerals. But mitochondrial function depends on all of these components working together, which is why a personalised approach to supplementation considers the full picture rather than isolated ingredients.

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Key takeaways

  1. CoQ10 exists in two interconvertible forms: ubiquinone (oxidised) and ubiquinol (reduced). Your body continuously cycles between them.
  2. In healthy individuals, 90–98% of circulating CoQ10 is already in the ubiquinol form, regardless of which form is supplemented.
  3. Bioavailability differences between the two forms are largely attributable to formulation technology, not the CoQ10 form itself.
  4. Ubiquinone is more chemically stable than ubiquinol, making it better suited to microgranule delivery and long-term storage.
  5. The majority of landmark CoQ10 clinical trials — including Q-SYMBIO — used ubiquinone, not ubiquinol.
  6. CoQ10 does not carry EU-authorised health claims. All efficacy statements are based on clinical trial evidence.
  7. PARTICULAR uses ubiquinone (50–100 mg) for its stability, evidence base, and bioequivalence in healthy individuals.
  8. Ubiquinol may offer advantages for older adults or those with impaired redox capacity, but for most people, the premium price is not justified by the evidence.

Sources cited in this article: