Randomization, blinding, and intervention
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ADVERSE EFFECTS
Following a 2-week run-in period, the participants were randomly allocated to the “L-carnitine + synbiotic” or “L-carnitine + placebo” groups via block randomization in a 1:1 ratio, in blocks of two, stratified by age, using the Random Allocation Software (RAS). Intervention allocation was blinded for the participants and researchers; to assure concealment, participants’ allocation was performed via consecutively numbered, opaque, sealed envelopes, by an investigator not involved in the study. The L-carnitine + synbiotic intervention group received two L-carnitine tablets/day (500 mg of L-carnitine tartrate/tablet, Karen Company, Iran) after the main meals, plus multistrain/multispecies synbiotic [Probiotics International Ltd. (ProtexinParticipants received the supplements/placebo in monthly visits. Placebo and synbiotic capsules were identical in color, shape, and size. To ensure adherence and discuss possible adverse effects, subjects received twice weekly phone calls and were asked to mention the side effects and to return the unused tablets/capsules. Compliance, described as taking at least 90% of the supplements, was assessed by the returned pill count (