In New Zealand, at least 10 brands of coenzyme Q10 (CoQ10) supplement are available over the counter from health food shops, pharmacies, and the Internet. These products claim that supplementation with coenzyme Q10 increases energy, wellbeing, stamina and muscle performance, strengthens the heart, and scavenges free radicals. The evidence for these effects is equivocal and well-controlled studies are needed. It is also necessary to confirm the bioavailability of the available CoQ10 supplements.

Coenzyme Q10 is an essential cofactor in the mitochondrial electron transport chain and also acts as an antioxidant, sparing, the α-tocopheroxyl radical.1 In mammals, CoQ10 is synthesised in all cells—and the diet is also a source, with meat being the biggest contributor.2

It is unlikely that many healthy New Zealand adults are frankly deficient in CoQ10, but CoQ10 deficiency has been associated with various diseases including Alzheimer’s disease and Parkinson’s disease. It is also possible that diseases producing oxidative stress may result in CoQ10 depletion. HMG-CoA reductase inhibitor (statin) therapy also decreases CoQ10 synthesis3 and causes a potential CoQ10 deficiency, due to inhibition of the common biosynthetic pathway for cholesterol and CoQ10. Thus, CoQ10 is relevant to at least 100,000 New Zealand patients currently on statin therapy.

The available CoQ10 supplements have different formulations, which may affect absorption.4–6 In particular, supplements in which CoQ10 is dispersed in oil generally have higher bioavailability than those formulated as dry powder tablets.4,6

Therefore we have compared the bioavailability of seven different coenzyme Q10 supplement brands, and provide a basis for selecting brand(s) for clinical use.

Ten healthy adult male volunteers were enrolled in a study approved by the Canterbury Ethics Committee. Participants were excluded if they had taken CoQ10, any vitamin supplements, or medications within the previous 4 weeks. The mean age was 24.2 years (range 21–28 years), the mean height was 179.8 cm (range 173–187 cm), and the mean weight was 71.8 kg (range 60–100 kg). The study was completed between November 2003 and January 2004.

Baseline blood samples were obtained after a 10-hour overnight fast, and CoQ10 supplements were administered as a single nominal dose of 150 mg, with supplement brands given in a different randomised order for each participant and a 1-week washout period between trial days. After administration of the supplement, a standardised vegetarian breakfast and lunch were provided, containing approximately 3 μg of coenzyme Q10.2 Lunch was provided as a takeaway package, and participants were permitted to leave the study centre after breakfast. A second blood sample was collected after 6 hours.

The brands investigated were selected because they are ‘popular’ brands that contain differing excipients and are outlined in Table 1, which also shows the measured CoQ10 content (n=6 capsules or tablets).

(Click here to view Table 1 and Table 2)

Blood specimens were collected and lithium heparin plasma was stored at -80°C until analysis. CoQ10 was analysed using a method similar to that used by Tang et al.7 The within- and between-run coefficients of variation (CV) for the CoQ10 assay are approximately 3.3%. Plasma lipids were determined by routine clinical methods. The differences between CoQ10 supplements were tested using either the non-parametric Friedman test or Wilcoxon signed-rank test (as appropriate), with statistical significance inferred when p<0.05. All CoQ10 supplement brands tested contained at least the claimed CoQ10 (Table 2).

Mean baseline lipids (±SD) for all participants were 4.81±1.04, 2.78±0.75, 1.18±0.30, and 1.28±0.44 mmol/L for total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides respectively. Mean baseline CoQ10 (±SD) was 0.85±0.25 μmol/L. During the trial there was no significant change in baseline levels of CoQ10, direct LDL cholesterol, HDL cholesterol, triglycerides, or total cholesterol, thus confirming that the wash-out period was sufficient.

There was no significant effect of CoQ10 supplementation on total cholesterol (p=0.539), triglycerides (p=0.128), or direct LDL and HDL cholesterol (p=0.910 and 0.587 respectively).

There was a significant difference (p=0.003) in CoQ10 absorption between the 10 participants (Figure 1). Some participants efficiently absorbed CoQ10 from most brands of the supplements, while others showed inefficient absorption. There was no correlation (p=0.56) between baseline CoQ10 levels and absorption of CoQ10.

There was a significant difference in bioavailability between the seven CoQ10 brands (p<0.001), with Q-Gel being significantly better than any other supplement (p=0.013). This is summarised in Table 2.

There was a significant difference in the delta CoQ10 to direct LDL cholesterol and CoQ10 to total cholesterol ratios between the supplement brands (p=0.001 for both), thus mirroring the differences in total CoQ10 (Table 2).

There was a significant correlation between baseline LDL concentrations and change in CoQ10 (p=0.004; R=+0.343), between total cholesterol levels and change in CoQ10 (p=0.004; R=+0.338), and also between baseline triglycerides and change in CoQ10 (p=0.035; R=+0.253). Therefore, higher LDL cholesterol or triglyceride concentrations may aid absorption of CoQ10. There was no correlation between HDL cholesterol, weight, or body mass index and mean CoQ10 absorption.

Although there are many different CoQ10 supplements available, there are little data on the prevalence and effect(s) of CoQ10 deficiency, or the benefits of CoQ10 supplementation. It is also necessary to confirm that the available CoQ10 supplements do in fact increase CoQ10 levels before advocating clinical use or attempting clinical trials.

There is also controversy about whether plasma (and hence dietary) CoQ10 is delivered to the mitochondria, but it is much easier to measure plasma levels than tissue level, and it is often assumed that tissue levels mirror those of plasma. However, Niklowitz et al8 found a positive correlation between CoQ10 in plasma and platelets, which contain mitochondria, implying that raising plasma levels of CoQ10 by diet and supplementation also raises tissue levels.

CoQ10 supplementation is well tolerated and dosages as high as 1200 mg/day have been administered with minimal side effects.9

We found important differences in the bioavailability of these supplements. However, the mean increase in plasma total CoQ10 of 0.41 µmol/L equates to about 0.7 mg of CoQ10 being absorbed into the blood from the 150 mg supplied. This can be compared to the normal diet in which CoQ10 is limited to about 3 to 5 mg per day, mainly via the consumption of meats rather than fruits and vegetables.2

Because CoQ10 is lipid soluble, it is likely that administration as a dispersion (or solubilised) in oil will aid absorption, as found in our study. The high bioavailability of Q-Gel compared to other coenzyme Q10 supplement brands supports the findings of Chopra et al5 who found the absorption of Q-Gel to be 319% better than that from a standard softgel capsule containing Q10 in oil, after 3 weeks of a daily 120 mg dose. Chopra et al5 also found the absorption from powder-filled hardshell capsules and powder-based tablets to be higher (125% and 128% respectively) than that from a standard softgel capsule.

Miles et al4 found the increase of plasma total CoQ10 by ‘solubilised’ supplemental CoQ10 to be 858%–1058% higher than that from a dry powder formulation. Furthermore, Wahlqvist et al6 found that the bioavailability of CoQ10 in a complex micelle emulsion (in a soft gelatine capsule) was 927% higher than a crystalline CoQ10 supplement with magnesium stearate (as an excipient and a hard gelatine capsule).

Thus it is clear that there are important differences. There is at least a four-fold variation in the increase in plasma CoQ10 achieved by different supplements, and some people get no increase when they take the less effective supplements at typical doses.

The high bioavailability of Q-Gel may be due to the presence of both non-ionic surfactants and the natural surfactant lecithin. The Radiance and Blackmores brands showed the next highest bioavailability, and these brands also contain lecithin.

Significant between subject differences in absorption have been previously reported,10–12 and highlight a need for monitoring of CoQ10 levels during supplementation. There was no correlation between weight, body mass index or baseline CoQ10 and CoQ10 absorption—hence there are no simple clinical indicators that accurately predict response to different supplement formulations. Therefore, monitoring of plasma CoQ10 concentration appears to be the only method to estimate CoQ10 absorption.

There are important differences in bioavailability between the available CoQ10 supplements and also significant inter-individual differences. We therefore recommend monitoring of plasma CoQ10 levels during supplementation, and that differences in bioavailability are considered when selecting a supplement. In this study, the Q-gel brand showed significantly better bioavailability than the six other CoQ10 supplements tested.