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Adverse Effects / Side Effects / Safety of CoQ10

Documented side effects associated with the use of CoQ10 in doses ranging anywhere from 30 mg to as high as 1,200 mg day in humans have been minor and are related to gastrointestinal problems.14,20 They include epigastric discomfort (discomfort in the upper / middle region of the abdomen) , appetite suppression, nausea and diarrhea in a very small number of cases. One interesting observation is that ingestion of CoQ10 late in the evening might cause insomnia 15 and this may be due to increased energy levels.

Even though the chance of adverse side effects is slight, there are two things that we suggest when taking Coenzyme Q10. First, take your CoQ10 with a meal. Taking your CoQ10 with food not only helps prevent stomach upset but actually aids in the absorption of CoQ10. Second, “front load” your dosage to the earlier part of the day – for example, if you were taking 400mg per day, you might want to consider taking 200mg with breakfast, 100mg with lunch and 100mg with dinner (early if possible!).

Is the safety of high dose CoQ10 supplementation well-documented?

Yes. The safety of high doses of orally-ingested CoQ10 in the form of ubiquinone over long periods is very well documented in the literature.14,23 The only side effects reported with a small number of subjects are mild gastrointestinal symptoms such as nausea and stomach upset.14,17,23 In a recent study, doses as high as 3000 mg a day were found to be safe and tolerable in patients with Parkinson’s disease.8 According to Hathcock, et al 45 the observed safe level (OSL) of CoQ10 for chronic administration as a dietary supplement is 1200 mg/day. In a recent trial on the safety of CoQ10 in its reduced form as ubiquinol in human subjects, dosages of up to 300 mg daily for two months was found to be safe.43 Higher dosages were not tested in this study.

Safety data on high dose CoQ10 ingestion are also available based upon animal studies. In one study with rats, long term ingestion of CoQ10 at doses up to 1200 mg/kg body weight was found to be safe and well tolerated.46 In another study on the in vivo and in vitro mutagenic potential of CoQ10 based upon mouse bone marrow micronucleus, chromosomal aberration, and bacterial reverse mutation tests, CoQ10 did not exhibit any clastogenic activity when administered orally to mice at doses up to 2000 mg/kg/day. In addition, the CoQ10 did not induce chromosomal aberrations in CHL/IU cells exposed to high concentrations, nor did it induce reverse mutations in S. typhimurium and E. coli.47

8. Shults CW, Flint Beal M, Song D, Fontaine D. Pilot trial of high dosages of coenzyme Q10 in patients with Parkinson's disease. Exp Neurol. 2004;188:491-4.

14. Sinatra ST. In: The Coenzyme Q10 Phenomenon. Keats Publishing, New Canaan, CT, 1998.

15. Pepping J. Coenyzme Q10. American Journal of Health-System Pharmacy 1999;56:519-521.

17. Fuke C, Krikorian SA, Couris RR. Coenzyme Q10: A review of essential functions and clinical trials. US Pharmacist 2000;25:1-12.

20. Greenberg S, Frishman WH. Co-enzyme Q10: a new drug for cardiovascular disease. J Clin Pharmacol 1990;30:596-608.

23. Langsjoen PH, Langsjoen AM. Overview of the use of coenzyme Q10 in cardiovascular disease. Biofactors 1999;9:273-84.

45. Hathcock J. ,Shao A. Risk assessment for coenzyme Q10 (Ubiquinone). Regul Toxicol Pharmacol. 2006;45:282-8.

46. Williams KD, Maneke JD, Abdelhameed M, Hall RL, Palmer TE, Kitano M, Hidaka T. 52-Week oral gavage chronic toxicity study with ubiquinone in rats with a 4-week recovery. J Agric Food Chem. 1999;47:3756-63.

47. Kitano M, Hosoe K, Fukutomi N, Hidaka T, Ohta R, Yamakage K, Hara T. Evaluation of the mutagenic potential of ubidecarenone using three short-term assays. Food Chem Toxicol. 2006;44:364-70.