Supplement
Coenzyme Q10
CoQ10 is a mitochondrial electron-transport cofactor whose levels fall with age and with statin therapy, making it a perennial of the longevity aisle. Unusually for that aisle, it has randomised trials with hard endpoints — in specific populations that look nothing like the typical healthy buyer.
Quick verdict
In chronic heart failure, the Q-SYMBIO trial found fewer major cardiac events on CoQ10 as adjunct therapy. In elderly Swedes with low selenium status, combined selenium and CoQ10 reduced cardiovascular mortality with effects persisting years later. Both are specific clinical contexts; evidence for healthy adults taking CoQ10 for ageing is absent.
The assessment
Claim by claim
Each claim is graded on its own evidence. A grade for one claim says nothing about the others.
| Claim | What was measured | Evidence |
|---|---|---|
| Improves outcomes as an adjunct treatment in chronic heart failure | Disease outcome | Early |
| Combined with selenium, reduces cardiovascular mortality in elderly people with low selenium status | Disease outcome | Early |
| Slows ageing in healthy adults | Lifespan | Insufficient |
Improves outcomes as an adjunct treatment in chronic heart failure
Early human evidenceOutcome measured: Disease outcome — A diagnosed condition or clinical event was measured.
Q-SYMBIO randomised 420 heart-failure patients to CoQ10 or placebo alongside standard therapy for two years and reported fewer major adverse cardiovascular events and lower cardiovascular mortality. A positive hard-endpoint trial — modest in size, awaiting modern replication, and about treating disease, not preventing ageing.
Why this grade — the appraisal in full
One or a small number of small, short or preliminary human studies. Directionally interesting, not yet dependable.
- Strongest study design. Randomised controlled trial with 420 participants.
- Human research volume. 1 human study, 420 participants in total.
- What was measured. 1 human study measured a clinical or functional outcome rather than a laboratory marker alone.
- Replication. The supporting result has not been independently replicated in humans.
- Study duration. Longest human study ran 104 weeks.
- Funding and conflicts. 1 of 1 human studies were funded by, or authored by, a party with a commercial interest in the result.
Limitations. Single trial of 420 patients recruited across many small sites; heart-failure background therapy has changed since.
| Study | Design | Population | Finding |
|---|---|---|---|
| [1]The effect of coenzyme Q10 on morbidity and mortality in chronic heart failure: …JACC. Heart failure · 2014 · PMID 25282031 | Randomised controlled trialHuman | 420 participantsParticipants with a diagnosed condition | Supports the claimQ-SYMBIO: fewer major adverse cardiovascular events with CoQ10 as adjunct heart-failure therapy. |
Combined with selenium, reduces cardiovascular mortality in elderly people with low selenium status
Early human evidenceOutcome measured: Disease outcome — A diagnosed condition or clinical event was measured.
The Swedish KiSel-10 trial gave community-dwelling elderly people selenium plus CoQ10 or placebo for four years; cardiovascular mortality was lower in the treated group, with the difference still visible twelve years on. The catch for supplement buyers: it was a combined intervention in a low-selenium population — Sweden's soils are selenium-poor — so it cannot tell you what CoQ10 alone does, or what happens in selenium-replete people.
Why this grade — the appraisal in full
One or a small number of small, short or preliminary human studies. Directionally interesting, not yet dependable.
- Strongest study design. Randomised controlled trial with 443 participants.
- Human research volume. 1 human study, 443 participants in total.
- What was measured. 1 human study measured a clinical or functional outcome rather than a laboratory marker alone.
- Replication. The supporting result has not been independently replicated in humans.
- Study duration. Longest human study ran 208 weeks.
Limitations. Combined intervention; low-selenium population; single trial from one group.
| Study | Design | Population | Finding |
|---|---|---|---|
| [2]Still reduced cardiovascular mortality 12 years after supplementation with selen…PloS one · 2018 · PMID 29641571 | Randomised controlled trialHuman | 443 participantsMixed population | Supports the claimKiSel-10 12-year follow-up: reduced cardiovascular mortality after 4 years of combined selenium + CoQ10. |
Slows ageing in healthy adults
Insufficient evidenceOutcome measured: Lifespan — Death from any cause was measured.
The claim on the label has no trial behind it: no study has tested CoQ10 against ageing-relevant endpoints in healthy adults.
Why this grade — the appraisal in full
Too little credible research exists to judge the claim either way.
- Available research. No usable studies are linked to this claim.
Limitations. Untested in the population that buys most of it.
Human evidence
2 studies in people.
- [1]Randomised controlled trial · 420 participants
- [2]Randomised controlled trial · 443 participants
Animal and laboratory evidence
Shown separately, and never used to support a human claim.
No preclinical study is currently linked on this page.
Before anything else
Safety and interactions
Well tolerated in trials. Interacts with warfarin (reduces its effect) — a genuinely important interaction for exactly the older population most likely to buy it.
The ledger
Grade history
22 August 2026
First published appraisal of this claim. Study links added: PMID 25282031.
22 August 2026
First published appraisal of this claim. Study links added: PMID 29641571.
22 August 2026
First published appraisal of this claim.
Falsifiability
What would change our view
Replication of Q-SYMBIO in modern heart-failure care, or any randomised evidence in healthy adults on ageing-relevant endpoints.
Check everything
Sources
Every citation links to its PubMed record. Bibliographic details are retrieved from PubMed, not written by us.
- [1]The effect of coenzyme Q10 on morbidity and mortality in chronic heart failure: results from Q-SYMBIO: a randomized double-blind trial Mortensen SA et al.. JACC. Heart failure. 2014. PMID 25282031 · doi:10.1016/j.jchf.2014.06.008
- [2]Still reduced cardiovascular mortality 12 years after supplementation with selenium and coenzyme Q10 for four years: A validation of previous 10-year follow-up results of a prospective randomized double-blind placebo-controlled trial in elderly Alehagen U et al.. PloS one. 2018. PMID 29641571 · doi:10.1371/journal.pone.0193120