The KiSel-10 trial
KiSel-10 is the Swedish trial behind the strongest longevity claim made for coenzyme Q10 (CoQ10): older people given CoQ10 together with selenium had about half the cardiovascular deaths of those on placebo, and the gap was still there twelve years later. It is a real and striking result, but it comes from one modest-sized, single-centre trial, part-funded by a supplement maker, and it cannot tell you whether the CoQ10, the selenium or the pair did the work.
Treat KiSel-10 as a promising lead for older people with low selenium, not as proof that CoQ10 extends life. Its own authors call it hypothesis-generating, and the selenium given alongside makes the CoQ10 share impossible to separate.
What the trial tested
KiSel-10 was a randomized, placebo-controlled trial in 443 community-dwelling Swedes aged 70–88. The active group took 200 mg a day of CoQ10 plus 200 µg a day of selenium yeast for four years; the comparison group took placebo.[1]
CoQ10 is a fat-soluble molecule the body makes itself; it carries electrons in mitochondria, the cell's power plants, and works as an antioxidant in cell membranes. Selenium is a trace mineral the body needs for glutathione peroxidase and thioredoxin reductase, enzymes that keep the cell's balance between oxidized and reduced molecules in check.
One detail is often misreported. Selenium status was measured but was not an entry criterion: the trial did not select selenium-deficient people. The cohort simply turned out to have low average selenium.
The trial used plain ubiquinone, the ordinary oxidized form of CoQ10, not the pricier ubiquinol. See Ubiquinol for why that matters to buyers.
The main result: fewer cardiovascular deaths
Over about five years of follow-up, cardiovascular deaths were roughly halved: 5.9% in the active group against 12.6% on placebo. The active group also had lower levels of NT-proBNP (N-terminal pro-B-type natriuretic peptide), a blood marker of heart strain, and a better heart-function score on ultrasound.[2]
The effect persisted through a twelve-year follow-up, long after the supplements stopped: cardiovascular deaths were 28.1% against 38.7%. The hazard ratio was 0.59, meaning the risk of cardiovascular death at any point was about 0.6 times that on placebo — about 40% lower.[3]
The follow-up analyses
- Inflammation, kidneys and sex. A later re-analysis found less inflammation and oxidative stress and better kidney function in the supplemented group. In this exploratory analysis, the mortality benefit looked larger in women than in men.[4]
- Telomeres. A sub-study found that leukocyte telomere length — the protective caps on the chromosomes of white blood cells, which shorten with age — was preserved in the active group while it shortened in the placebo group. It is a rare human readout linking supplementation to a marker of cellular aging, though it cannot be separated from the selenium co-treatment.[5]
Why to hold it loosely
- One trial, one centre, modest size. The authors themselves call the result hypothesis-generating for exactly these reasons.
- Two supplements at once. Every result belongs to the combination. Nothing in KiSel-10 shows what CoQ10 alone would do, and selenium on its own has narrow uses and a real upper limit.
- Industry support. KiSel-10 was supported by Pharma Nord, which supplied the exact branded products used. Together with the heart-failure trial Q-SYMBIO, it is one of only two trials that moved a hard endpoint for CoQ10, and both carry CoQ10-industry sponsorship.
- A low-selenium population. Whatever worked may depend on the low average selenium of this cohort. It says little about well-nourished adults, and in the general population large observational data show no mortality benefit from CoQ10 use (see Coenzyme Q10).
What to do
- Don't read KiSel-10 as a reason for healthy adults to take CoQ10. The result is in older people with low selenium, from one modest-sized trial.
- If you are over 70 and considering the combination, discuss it with your doctor, including your selenium status and any other selenium you take, since selenium has a real upper limit.
- If you do take it, the trial used plain ubiquinone, 200 mg a day, together with 200 µg of selenium; you do not need a premium form. Take it with a meal containing fat.
Further reading
- Alehagen U et al. 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 (KiSel-10). Int J Cardiol 2013.[6]
- Alehagen U et al. 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. PLoS One 2018.[7]
- Alehagen U et al. Selenium and Coenzyme Q10 Supplementation and Sex Differences in Cardiovascular Mortality Results from a Prospective Randomized Double-Blind Placebo-Controlled Trial in Elderly People Low in Selenium. Antioxidants (Basel) 2025.[8]
- Opstad TB et al. Selenium and Coenzyme Q10 Intervention Prevents Telomere Attrition, with Association to Reduced Cardiovascular Mortality-Sub-Study of a Randomized Clinical Trial. Nutrients 2022.[9]