In recent years, it has been suggested that nutritional deficiencies may be of causal relevance in individuals with ME/CFS. These include deficiencies of vitamins and trace elements. It is likely that the observed nutritional deficiencies contribute to the core symptoms of the disease. Coenzyme Q10 (CoQ10) has been studied as an alternative and complementary therapy in ME/CFS for fatigue, pain, tiredness, neurocognitive impairment, and sleep problems. This demonstrates how alterations in energy metabolism, mitochondrial dysfunction, oxidative stress, imbalance of the immune-inflammatory response, and activation of the NLRP3 inflammasome are likely consequences of low levels of CoQ10 and selenium, which are related to the main symptoms in ME/CFS. Hypothesis: CoQ10 and selenium levels are decreased in ME/CFS patients. A natural therapeutic alternative in the treatment of common symptoms in ME/CFS could be the oral CoQ10 (Ubiquinone) plus selenium supplementation to module redox status and inflammation response in ME/CFS. Aims: To evaluate the efficacy of oral Ubiquinone + selenium supplementation on clinical outcome and circulating biomarkers in ME/CFS. We enrolled 42 ME/CFS patients diagnosed according to the 1994 CDC/Fukuda criteria who have received oral treatment of 400 mg Ubiquinone + 200 microgram selenium daily for 8 weeks. Demographic, clinical characteristics and laboratory variables, and validated outcome measures to perceived fatigue, sleep disturbances, and quality of life will be also evaluated. In addition, plasma biomarkers related to oxidative stress status (total antioxidant capacity and lipoperoxide levels), inflammatory response (pro-and anti-inflammatory cytokines), and cardiovascular dysfunction (FGF-21 and NT-proBNP) will be assayed.

Inclusion Criteria:

• Patients were potentially eligible if they were female, aged 18 years or older, and had a confirmed diagnosis of ME/CFS by a specialist according to the 1994 CDC/Fukuda criteria

Exclusion Criteria:

• Exclusion criteria were those with any significant active fatiguing medical disorder (thyroid-related disorders, sleep apnea, narcolepsy, medication side-effects, heart diseases, iron deficiency anemia), previous diagnosis not unequivocally resolved (chronic hepatitis, malignancy), autoimmune disorders, history of past/current neuropsychiatric disorders (major depressive disorder, psychotic or melancholic features, bipolar disorder, schizophrenia, delusional disorder, dementias, anorexia nervosa, and bulimia nervosa), and participation in another clinical trial of the same or different nature within 30 days prior to study inclusion; inability (in the opinion of the investigator) to follow the instructions or to complete the treatment satisfactorily; failure to provide signed informed consent; use of certain drugs and supplements that might influence outcome measures in the last 90 days or whose withdrawal might be a relevant problem, anticoagulant treatment, pregnancy or breast-feeding, smoking habits, alcohol intake or substance abuse, strong hormone-related medications, and obesity.