CoQ10, what it is and what the research says

By Dr Conor Kerley, PhD, cardiovascular and nutrition researcher.

A molecule that turns up in almost every cell you own was first pulled out of a cow's heart, and the reason it is sold in a capsule at all is that there is no plate of food that will get you there.

In 1957, at the Enzyme Institute at the University of Wisconsin, a young biochemist named Frederick Crane was working his way through beef hearts. There was a practical reason for that: heart muscle is dense with mitochondria, the compartments inside a cell where energy gets made, so if you need them in quantity you go to a butcher. Out of the extract came a yellow, fat-soluble substance that nobody had a name for, published as a two-page note, Isolation of a quinone from beef heart mitochondria. A year later Karl Folkers and his team at Merck worked out what it was: a quinone ring with a tail of ten isoprene units, which is where both halves of the name come from. British researchers circling the same compound had already called it ubiquinone, because it seemed to be everywhere they looked. They were right: it is in you now, in more or less every cell you have.

The job itself is unglamorous and relentless: cells pull energy out of food by passing electrons down a chain of steps, and CoQ10 is one of the parts that moves them along, picking electrons up at one step, carrying them a short distance and handing them on [1]. That has been settled biochemistry since the decade Crane published, and it is the reason anyone thought the molecule worth testing in people at all.

Three to six milligrams

The number that decides everything else about CoQ10 is the one almost nobody leads with. You make nearly all of your own: your cells build it through a long chain of steps, and that internal supply is where essentially all of it comes from [1]. Food barely participates. The best dietary sources are meat, oily fish, nuts and a few oils, and even eating well the average person takes in somewhere between 3 and 6 mg a day [2], which makes a single 100 mg capsule fifteen to thirty times an entire day's eating.

That is not how nutrients usually work, and the difference is worth being explicit about, because I think it is the whole reason a capsule is a different proposition here. For most things in a formula like this one, food is a genuine route and the supplement a convenience: you can eat your way to the vitamin C or the magnesium if you care to, and the capsule only saves you the trouble. There is no eating your way to CoQ10, because you were never really eating it, you were making it, and the gap between a plate of food and a capsule is not a matter of effort but a difference in order of magnitude that no diet closes. Whether closing it matters is a separate question, and a harder one, from whether it can be done at all.

The gap is the first thing to notice about the trials. KiSel-10 gave 443 older people in Sweden 200 mg of CoQ10 a day alongside selenium for four years, and deaths from heart-related causes came in at about 6% in the supplemented group against about 13% on placebo [3]. Q-SYMBIO used 300 mg a day in 420 patients over two years, and serious heart events reached 15% against 26% on placebo [4]. A 2024 review pooled 33 trials in heart failure and reported lower death rates and fewer admissions [5]. Whatever those numbers prove to be worth, 200 and 300 mg a day are thirty to a hundred times what food supplies, so nothing here is testing a dietary intake. It is all testing something food cannot do.

The premium and the step

Ubiquinol and ubiquinone are the same molecule wearing two different hats. Ubiquinone is the version that has handed its electrons on, ubiquinol the version holding them, and inside you they flip back and forth constantly, because that flipping is the job [1]. Ubiquinol is the more expensive one, and the pitch behind the price is intuitive to the point of being hard to argue with: it is the form your cells use, so surely it is the form to swallow. Then somebody measured it.

Pravst 2020 is the largest of the head-to-head comparisons [6]. Twenty-one healthy adults aged 65 to 74 took single 100 mg doses of several formulations, with blood sampled over the following two days, and two things came out of it. The first settles the argument as far as I am concerned: CoQ10 turned up in the blood mostly as ubiquinol even in the people who swallowed ubiquinone [6]. The gut does the conversion, which means the premium buys a step the body performs for free.

The second finding is more interesting than the first. What separated the products was not the word on the label but what the CoQ10 had been dissolved in, and a water-soluble ubiquinone syrup produced the highest blood levels of anything tested, ubiquinol included [6]. López-Lluch 2019 points the same way: fourteen volunteers took seven different 100 mg products in turn, the differences were large, and the carrier and the solubilisation did the separating [7].

Two smaller trials do put ubiquinol ahead. Langsjoen 2014 gave twelve people each form for four weeks and measured higher blood levels on ubiquinol [8], and Zhang 2018 gave ten older men each form for two weeks, blinded, and reported higher CoQ10 status on ubiquinol [9]. Twelve people and ten, against twenty-one and fourteen pointing the other way, is not a vast literature in either direction. But the shape of it is clear enough, and it is not the shape the shelf suggests: what decides whether a CoQ10 product gets anything into the blood is how it has been formulated and how much is in it [6,7], and neither is a word you can read off the front of a box.

Which is where Crane's beef hearts leave us. Whatever you swallow, what arrives is the same yellow molecule he pulled out of a mitochondrion in 1957, and it arrives mostly as ubiquinol, because the body sorted that out a long time before anyone thought to charge you for it.

References

1. Crane FL. Biochemical functions of coenzyme Q10. J Am Coll Nutr. 2001;20(6):591–598. PMID 11771674.
2. Pravst I, Žmitek K, Žmitek J. Coenzyme Q10 contents in foods and fortification strategies. Crit Rev Food Sci Nutr. 2010;50(4):269–280. PMID 20301015.
3. Alehagen U, Johansson P, Björnstedt M, Rosén A, Dahlström U. Cardiovascular mortality and N-terminal-proBNP reduced after combined selenium and coenzyme Q10 supplementation: a 5-year prospective randomized double-blind placebo-controlled trial among elderly Swedish citizens. Int J Cardiol. 2013;167(5):1860–1866. PMID 22626835.
4. Mortensen SA, Rosenfeldt F, Kumar A, Dolliner P, Filipiak KJ, Pella D, Alehagen U, Steurer G, Littarru GP; Q-SYMBIO Study Investigators. The effect of coenzyme Q10 on morbidity and mortality in chronic heart failure: results from Q-SYMBIO: a randomized double-blind trial. JACC Heart Fail. 2014;2(6):641–649. PMID 25282031.
5. Xu J, Xiang L, Yin X, Song H, Chen C, Yang B, Ye H, Gu Z. Efficacy and safety of coenzyme Q10 in heart failure: a meta-analysis of randomized controlled trials. BMC Cardiovasc Disord. 2024;24(1):592. PMID 39462324.
6. Pravst I, Rodríguez Aguilera JC, Cortes Rodriguez AB, Jazbar J, Locatelli I, Hristov H, Žmitek K. Comparative bioavailability of different coenzyme Q10 formulations in healthy elderly individuals. Nutrients. 2020;12(3):784. PMID 32188111.
7. López-Lluch G, Del Pozo-Cruz J, Sánchez-Cuesta A, Cortés-Rodríguez AB, Navas P. Bioavailability of coenzyme Q10 supplements depends on carrier lipids and solubilization. Nutrition. 2019;57:133–140. PMID 30153575.
8. Langsjoen PH, Langsjoen AM. Comparison study of plasma coenzyme Q10 levels in healthy subjects supplemented with ubiquinol versus ubiquinone. Clin Pharmacol Drug Dev. 2014;3(1):13–17. PMID 27128225.
9. Zhang Y, Liu J, Chen XQ, Oliver Chen CY. Ubiquinol is superior to ubiquinone to enhance coenzyme Q10 status in older men. Food Funct. 2018;9(11):5653–5659. PMID 30302465.

Last reviewed: 10 September 2026. This article is educational and is not medical advice.