Coenzyme Q10 (CoQ10) plays a central role in mitochondrial oxidative phosphorylation. Several studies have shown the beneficial effects of dietary CoQ10 supplementation, particularly in relation to cardiovascular health. CoQ10 biosynthesis decreases in the elderly, and consequently, the beneficial effects of dietary supplementation in this population are of greater significance. However, most pharmacokinetic studies have been conducted on younger populations. The aim of this study was to investigate the single-dose bioavailability of different formulations of CoQ10 in a healthy geriatric population. A randomized, three-period, crossover bioavailability study was conducted on 21 healthy older adults (aged 65–74). The treatment was a single dose with a one-week washout period. Three different formulations containing the equivalent of 100 mg of CoQ10 were used: Q10Vital® water-soluble CoQ10 syrup (the investigational product—IP); ubiquinol capsules (the comparative product—CP); and ubiquinone capsules (the standard product—SP). Ubiquinone/ubiquinol was followed in the plasma for 48 h. An analysis of the ratio of the area under the baseline-corrected concentration curve (ΔAUC48) for total CoQ10 and a comparison to SP yielded the following: The bioavailability of CoQ10 in the IP was 2.4-fold higher (95% CI: 1.3–4.5; p = 0.002), while the bioavailability of ubiquinol (CP) was not significantly increased (1.7-fold; 95% CI: 0.9–3.1, p = 0.129). No differences in the redox status of the absorbed coenzyme Q10 were observed between formulations, showing that CoQ10 appeared in the blood mostly as ubiquinol, even if consumed as ubiquinone.

Coenzyme Q10 (CoQ10) deficiency is a rare disease characterized by a decreased accumulation of CoQ10 in cell membranes. Considering that CoQ10 synthesis and most of its functions are carried out in mitochondria, CoQ10 deficiency cases are usually considered a mitochondrial disease. A relevant feature of CoQ10 deficiency is that it is the only mitochondrial disease with a successful therapy available, the CoQ10 supplementation. Defects in components of the synthesis machinery caused by mutations in COQ genes generate the primary deficiency of CoQ10. Mutations in genes that are not directly related to the synthesis machinery cause secondary deficiency. Cases of CoQ10 deficiency without genetic origin are also considered a secondary deficiency. Both types of deficiency can lead to similar clinical manifestations, but the knowledge about primary deficiency is deeper than secondary. However, secondary deficiency cases may be underestimated since many of their clinical manifestations are shared with other pathologies. This review shows the current state of secondary CoQ10 deficiency, which could be even more relevant than primary deficiency for clinical activity. The analysis covers the fundamental features of CoQ10 deficiency, which are necessary to understand the biological and clinical differences between primary and secondary CoQ10 deficiencies. Further, a more in‐depth analysis of CoQ10 secondary deficiency was undertaken to consider its origins, introduce a new way of classification, and include aging as a form of secondary deficiency.