Background: There are reports showing that l-carnitine alone or in combination with other micronutrients improve sperm parameters. However, comparative studies are still lacking. This study was carried out to compare the short term effects of a combination of eight micronutrients including l-carnitine vs. a mono-substance (l-carnitine alone) on sperm parameters.

Methods: This was a prospective, open-labelled, nonrandomized study that included male subjects (20 to 60 years) with at least 1 year of subfertility and at least one pathological semen analysis who received 3 months treatment with a mono-substance (500 mg l-carnitine/twice a day, n = 156) or a combined compound (440 mg l-carnitine + 250 mg l-arginine + 40 mg zinc + 120 mg vitamin E + 80 mg glutathione + 60 μg selenium + 15 mg coenzyme Q10 + 800 μg folic acid/once a day, n = 143) for the same time period. Sperm parameters were analyzed before and after treatment and groups comparisons performed.

Results: Baseline characteristics were similar among studied groups (age and body mass indices). Semen parameters (volume, density, overall progressive motility [including slow and fast motility]) and percentage of sperm with normal morphology improved after 3 months in both groups as compared to baseline. However, relative change (expressed as % increase of absolute values) for sperm density and overall progressive motility (including fast motility) was found to be higher for the combined micronutrient treatment group as compared to the mono-treatment using l-carnitine alone.

Conclusion: Both analyzed groups displayed a positive short term effect on all sperm parameters; however effect on density and motility was significantly better for the combined formulation. There is need for more research in this matter that includes long term outcome data.

Trial registration: Retrospectively registered at ISRCTN (7th October 2016). Study ID: ISRCTN48594239.