What is the bioavailability of Coenzyme Q10 (CoQ10) when taken as ubiquinol compared to ubiquinone?

Bioavailability of Ubiquinol vs. Ubiquinone

Ubiquinol and ubiquinone are both absorbed in their original forms in the small intestine, with ubiquinol showing slightly superior bioavailability in older individuals, though individual responses vary significantly. 1, 2, 3

Forms and Conversion

• CoQ10 exists in two forms:
  • Ubiquinone (oxidized form)
  • Ubiquinol (reduced form)
• Both forms reach the small intestine mostly in their original state 2
• However, some conversion may occur during digestion:
  • Studies in dogs show increasing conversion of ubiquinol to ubiquinone as it passes through the GI tract 4
  • After absorption, ubiquinone is typically reduced back to ubiquinol in the body 4

Comparative Bioavailability

• Bioavailability varies significantly between individuals and formulations 5
• In older men, ubiquinol appears more effective at enhancing CoQ10 status:
  • A randomized crossover trial showed ubiquinol significantly increased plasma total CoQ10 1.5-fold after 2 weeks (200 mg/day)
  • Ubiquinone supplementation produced insignificant increases in plasma CoQ10 levels 3
• Individual response patterns were observed:
  • 6 of 10 subjects responded better to ubiquinol
  • 2 of 10 subjects responded better to ubiquinone 3

Factors Affecting Absorption

• The matrix used to dissolve CoQ10 significantly impacts bioavailability 5
• Formulation characteristics matter more than the form (ubiquinol vs. ubiquinone):
  • Soft-gel capsules containing either ubiquinone or ubiquinol showed the best absorption 5
  • Addition of preservatives like vitamin C affects bioavailability 5
• CoQ10 absorption is generally limited due to:
  • Hydrophobicity
  • Large molecular weight
  • Slow absorption process (peak plasma levels occur 5-10 hours after ingestion) 6, 1

Clinical Implications

• For therapeutic use, the standard range is 50-1200 mg/day for adults 6, 1
• For cardiovascular benefits, 100-200 mg/day is recommended 1
• Both forms appear safe with minimal side effects:
  • Single doses up to 300 mg and 4-week administration of 90-300 mg ubiquinol showed no safety concerns 7
  • Doses up to 3000 mg/day for 8 months have been well-tolerated 6

Key Takeaway

While both forms are absorbed, ubiquinol may offer slightly better bioavailability, particularly in older individuals. However, the formulation and carrier lipids may be more important determinants of absorption than whether the supplement is in ubiquinol or ubiquinone form. Individual physiological factors also play a significant role in determining which form will be better absorbed by a particular person.