Healthy eating

To stay as young as we can as late in life as possible, we need to eat right, exercise, and get a good night’s sleep. Then, a well-tested and well-documented Coenzyme Q10 supplement should be right at the top of the list of nutritional supplements that we take. As we get older, our bodies produce less and less Coenzyme Q10, and we cannot make up the difference through food alone.

Coenzyme Q10 supplements are so safe that I have not spent much time writing about their safety.  It would not be much of an exaggeration to say that Coenzyme Q10 supplements are as safe as water.  In fact, in study after study, there is no difference in side effects between the Coenzyme Q10 active treatment group and the placebo control group. 

We need a good Coenzyme Q10 status.  There are two primary reasons why Coenzyme Q10 supplementation provides heart health benefits:

  • Coenzyme Q10 is essential to the process of cellular energy production.
  • Coenzyme Q10 works as an antioxidant to protect the cells against the damage caused by harmful free radicals.

Let’s look at some of the studies.

Safety of Coenzyme Q10 in the Q-Symbio study
In 2014, Dr. Svend Aage Mortensen and a team of researchers published the results of the multi-center Q-Symbio study of the effect of Coenzyme Q10 supplementation on the morbidity and mortality of chronic heart failure patients.

Summary: The researchers randomly assigned 420 patients to an active treatment group receiving 300 milligrams of Coenzyme Q10 daily (100 milligrams with each meal) or to a control group receiving matching placebo capsules.  The study lasted two years.  It was a double-blind study; neither the researchers nor the patients knew who was getting the real Coenzyme Q10 until the study ended.

The Q-Symbio study results showed that taking 300 milligrams of Coenzyme Q10 a day for two years was just as safe as taking the placebo capsules.  The adjunctive treatment with Coenzyme Q10 improved the heart failure patients’ symptoms and reduced the incidence of major adverse cardiovascular events including death [Mortensen].

Safety of Coenzyme Q10 supplements in the KiSel-10 study
In the period 2013-2015, Professor Urban Alehagen and a team of researchers published the results of the KiSel-10 study.

Summary: The researchers randomly assigned 443 healthy senior citizens to a treatment group receiving 200 milligrams of organic high-selenium yeast daily or to a control group receiving matching placebos.  The study lasted four years.  It was also a double-blind study.

A 10-year follow-up of the study participants showed that the treatment with Coenzyme Q10 and selenium for four years was significantly associated with better heart function and with reduced cardiovascular mortality.  Not only were the patients who received the Coenzyme Q10 and selenium better protected during the study, they were also better protected in the years that followed the cessation of the treatment [Alehagen 2015].

In the KiSel-10 study as in the Q-Symbio study, the incidence of adverse effects from the treatment was very small and essentially the same in the active treatment group and in the control group.  Actually, the only adverse effects reported were some slight symptoms of diarrhea in both groups.  Those symptoms were most likely caused by the vegetable oil in the capsules, not by the Coenzyme Q10 itself [Alehagen 2013].

Safety in a well-documented Coenzyme Q10 supplement
Coenzyme Q10 supplements are safe to use.  The reason for choosing a well-documented Coenzyme Q10 supplement like the one used in the Q-Symbio study and in the KiSel-10 study is that the randomized controlled studies provide evidence of heart health benefits as well as evidence of safety.

Absorption of the Coenzyme Q10 supplements on the market in the United States varies much more than the safety of the supplements does.  Some, perhaps many of the Coenzyme Q10 supplements, may not give any significant health benefits because they have not been formulated properly for good absorption.  They are safe enough; they just don’t give any significant health benefit.

Formulation of the Coenzyme Q10 supplement most important
Spending good money for Coenzyme Q10 supplements is a gamble.  There may or may not be good absorption and good health benefits, again, depending on the formulation.  The best thing to do is to purchase a Coenzyme Q10 supplement that has been tested in a rigorous randomized controlled trial.

Safe daily intakes of Coenzyme Q10
The Micronutrient Information Center of the Linus Pauling Institute at Oregon State University summarizes the safety of Coenzyme Q10 supplements as follows:

  • no significant adverse side effects reported for Coenzyme Q10 supplements at daily doses as high as 1200 milligrams for 16 months [Shults]
  • no significant adverse side effects reported for Coenzyme Q10 supplements at daily doses as high as 600 mg/day for up to 30 months [Huntington Study Group]

Dr. Ikematsu and a group of researchers at Haradoi Hospital, Japan, tested the safety of various daily doses of Coenzyme Q10 in healthy adults.  Their results showed that Coenzyme Q10 intakes up to 900 milligrams per day were well-tolerated and safe [Ikematsu].

Hathcock and Shao have proposed that 1200 milligrams per day of Coenzyme Q10 should be regarded as the observed daily safe level for Coenzyme Q10 [Hathcock].

Coenzyme Q10 safe at levels above the effective levels
As we have seen, 900 and 1200 milligrams are far above the 200 – 300 milligrams per day that have been associated with heart protection benefits in both heart failure patients and in senior citizens.

  • The important thing is the formulation of the Coenzyme Q10 supplement.
  • Good formulation is difficult to achieve.
  • Good formulation leads to good absorption.
  • Good absorption leads to significant heart health benefits.


Read our key article about CoQ10 and cardiovascular health in elderly people



Alehagen, U., Johansson, P., Björnstedt, M., Rosén, A., & Dahlström, U. (2013). 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. International Journal of Cardiology, 167(5), 1860-1866.

Alehagen, U., Aaseth, J., & Johansson, P. (2015). Less increase of copeptin and MR-proADM due to intervention with selenium and coenzyme Q10 combined: Results from a 4-year prospective randomized double-blind placebo-controlled trial among elderly Swedish citizens. Biofactors (Oxford, England), 41(6), 443-452.

Alehagen, U., Aaseth, J., & Johansson, P. (2015). Reduced Cardiovascular Mortality 10 Years after Supplementation with Selenium and Coenzyme Q10 for Four Years: Follow-Up Results of a Prospective Randomized Double-Blind Placebo-Controlled Trial in Elderly Citizens. Plos One, 10(12), e0141641.
Hathcock, J.N. & Shao, A. (2006). Risk assessment for Coenzyme Q10 (Ubiquinone). Regul Toxicol Pharmacol., 45(3):282-288.

Huntington Study Group. (2001). A randomized, placebo-controlled trial of Coenzyme Q10 and remacemide in Huntington’s disease. Neurology, 57(3):397-404.

Ikematsu, H., Nakamura, K., Harashima, S., Fujii, K., & Fukutomi, N. (2006). Safety assessment of Coenzyme Q10 (Kaneka Q10) in healthy subjects: a double-blind, randomized, placebo-controlled trial. Regulatory Toxicology and Pharmacology: RTP, 44(3), 212-218.

Mortensen, S. A., Rosenfeldt, F., Kumar, A., Dolliner, P., Filipiak, K. J., Pella, D., & Littarru, G. P. (2014). The effect of coenzyme Q10 on morbidity and mortality in chronic heart failure: results from Q-SYMBIO: a randomized double-blind trial. JACC. Heart Failure, 2(6), 641-649.

Shults, C. W., Oakes, D., Kieburtz, K., Beal, M. F., Haas, R., Plumb, S., & … Lew, M. (2002). Effects of Coenzyme Q10 in early Parkinson disease: evidence of slowing of the functional decline. Archives of Neurology, 59(10), 1541-1550.

Disclaimer: The information presented in this article is not intended for use as medical advice and should not be construed as such.