What is Coenzyme Q10 (CoQ10)?

What is Coenzyme Q10 (CoQ10)?

Coenzyme Q10 (CoQ10) is a fat-soluble, vitamin-like compound synthesized in mitochondria that serves two critical functions: it acts as an essential electron carrier in cellular energy (ATP) production and functions as the only endogenously produced lipid-soluble antioxidant in the body. 1

Chemical Structure and Nomenclature

• CoQ10 is also called "ubiquinone" due to its quinone chemical structure and ubiquitous presence in virtually all human cells, animals, and bacteria 1
• The "Q" refers to the quinone chemical groups and the "10" indicates the number of isoprenyl subunits in its tail 1
• It exists in two forms: ubiquinol (reduced form) and ubiquinone (oxidized form) 1

Primary Biological Functions

Energy Production

• CoQ10 plays a fundamental role in mitochondrial bioenergetics as an electron and proton carrier, specifically mediating electron transport from complex I or II to complex III in the respiratory chain 1
• It is crucial in tissues with high energy requirements including the heart, skeletal muscles, kidneys, liver, and brain 1
• The body naturally produces approximately 500 mg/day of CoQ10 through endogenous biosynthesis 1, 2

Antioxidant Protection

• CoQ10 is present in all cellular membranes, high- and low-density lipoproteins, and mitochondria, protecting them against free radical damage generated during normal cellular metabolism 1
• It helps regenerate vitamin E to its active antioxidant form 1
• These antioxidant properties may enhance NO bioavailability and improve endothelial function 1

Additional Functions

• Gene regulation of overall tissue metabolism 1
• Neuroprotection through inhibition of glutamate release and calcium influx 1
• Possible immunomodulation effects 1

Synthesis and Dietary Sources

Endogenous Production

• CoQ10 is predominantly synthesized de novo in the human body at an estimated rate of 500 mg/day 1
• Endogenous biosynthesis declines with age 1
• Synthesis requires several components including mevalonate, tyrosine, riboflavin, folate, B12, and vitamin C 1

Dietary Intake

• Average daily nutritional intake is only 3-6 mg/day from food sources 1, 2, 3
• The richest nutritional sources are meat (especially beef heart with over 100 mg/kg), fish (sardines contain 5.1-64.3 mg/kg), nuts, and some oils 1, 4
• Much lower levels are found in dairy products, vegetables, fruits, and cereals 4

Absorption and Transport

• Intestinal absorption of CoQ10 is inherently low due to its hydrophobicity and large molecular weight 1, 3
• Peak plasma levels occur 5-10 hours after ingestion due to slow absorption kinetics 1, 3
• CoQ10 is transported in plasma by low-density lipoproteins (LDL), making plasma levels dependent on lipoprotein status 1, 3
• Taking CoQ10 with fat-containing meals significantly enhances absorption given its lipid-soluble nature 3
• A nonlinear absorption process exists, with plasma concentration decreasing as dosage increases 1

Clinical Deficiency Symptoms

Reported symptoms of CoQ10 deficiency include:

• Sore, aching muscles and muscle weakness 1, 2
• Fatigue and mental confusion 1
• Gingivitis 1
• Elevated blood pressure and high cholesterol levels 1
• Seizures, vision and/or hearing loss 1
• Kidney damage 1

Supplementation Dosing

• No DRI (Dietary Reference Intake) or RDA (Recommended Dietary Allowance) has been established for CoQ10 1, 2
• Studies have used doses ranging from 50-1200 mg/day in adults, with up to 3000 mg/day being well-tolerated 1, 2
• For children, doses up to 10 mg/kg/day have been studied 1
• The usual adult dose is 1 tablet by mouth once daily as prescribed 5
• Based on dose-response analysis, 100-200 mg/day appears sufficient to provide beneficial effects in patients with cardiometabolic disorders 1

Safety Profile

• CoQ10 supplementation demonstrates excellent safety with minimal adverse effects even at very high doses 6, 7
• The acceptable daily intake (ADI) is 12 mg/kg/day (720 mg/day for a 60 kg person), and the observed safety level (OSL) is 1200 mg/day 7
• The most common side effects are mild gastrointestinal symptoms including nausea, vomiting, diarrhea, and anorexia 1, 6
• Monitoring liver enzymes is recommended during supplementation, particularly at higher doses or with prolonged use 2, 6

Important Drug Interactions

• CoQ10 may interact with warfarin by increasing its metabolism through cytochrome P450 enzymes, though clinical evidence at 100 mg/day shows no effect on warfarin action 6
• The recommended approach is to avoid CoQ10 or monitor INR more frequently if supplementation is necessary, particularly at doses above 100 mg/day 6

Clinical Applications

CoQ10 supplementation has been studied in various conditions including:

• Cardiovascular diseases (heart failure, hypertension, myocardial infarction) 1, 8
• Neurological conditions (Parkinson's disease, Alzheimer's disease, migraine) 9, 10
• Muscle fatigue and chronic fatigue syndrome 2
• Mitochondrial disorders 2

However, supplementation studies have generally shown little benefit across various conditions, with primary deficiencies and mitochondrial diseases being exceptions 1

Formulation Considerations

• CoQ10 is available commercially as either ubiquinol (reduced form) or ubiquinone (oxidized form) 1
• No IV formulation currently exists, limiting options for patients unable to absorb oral supplements 1, 2, 3
• New preparations with increased water-solubility and structural derivatives like idebenone and MitoQ are being developed to improve absorption and tissue distribution 10