A low intake of selenium has been associated with increased cardiovascular mortality in some epidemiological studies. This could be reduced by supplementation with selenium and coenzyme Q10. D-dimer, a fragment of fibrin mirroring fibrinolysis, is a biomarker of thromboembolism, increased inflammation, endothelial dysfunction and is associated with cardiovascular mortality in ischemic heart disease.
The objective of this trial was to examine the impact of selenium and coenzyme Q10 on the level of D-dimer, and its relationship to cardiovascular mortality. D-dimer was measured in 213 individuals at the start and after 48 months of a randomised double-blind placebo-controlled trial with selenium yeast (200 µg/day) and coenzyme Q10 (200 mg/day) (n = 106) or placebo (n = 107). The follow-up time was 4.9 years.
All included individuals were low in selenium (mean 67 μg/L, SD 16.8). The differences in D-dimer concentration were evaluated by the use of T-tests, repeated measures of variance, and ANCOVA analyses. At the end, a significantly lower D-dimer concentration was observed in the active treatment group in comparison with those on placebo (p = 0.006). Although D-dimer values at baseline were weakly associated with high-sensitive CRP, while being more strongly associated with soluble tumour necrosis factor receptor 1 and sP-selectin, controlling for these in the analysis there was an independent effect on D-dimer.
In participants with a D-dimer level above median at baseline, the supplementation resulted in significantly lower cardiovascular mortality compared to those on placebo (p = 0.014). All results were validated with a persisting significant difference between the two groups.
The authors concluded that supplementation with selenium and coenzyme Q10 in a group of elderly low in selenium and coenzyme Q10 prevented an increase in D-dimer and reduced the risk of cardiovascular mortality in comparison with the placebo group. The obtained results also illustrate important associations between inflammation, endothelial function and cardiovascular risk.
These results are interesting and potentially important. The authors agree that their study is not fully conclusive: “Even if the size of the study population is small, we regard the results as being interesting from a scientific point of view, and for hypothesis-generating. The included participants represented a relatively narrow age stratum, so it is not possible to extrapolate the results to other age groups without uncertainty. Finally, as the evaluated population consisted of Caucasians who were low in selenium and coenzyme Q10, it is not necessarily true that the obtained results could be extrapolated to another population.” It might furthermore be of interest to note that part of the analysis cost was supported by grants from Pharma Nord Aps, Denmark, the County Council of Östergötland, Linköping University.
What is needed next, I think, are independent replications. Also of interest would be to determine whether the effects are due to the selenium, or the Q10, or both. And finally, one must caution consumers to not overdose on selenium which could have a host of negative effects on health.