Efficacy of L-arginine and combination with garlic extract for migraine prevention in Australian adults

This study will test whether a nutritional supplement approach can help reduce migraines in adults who experience frequent episodic migraines. Participants will take either L-arginine alone or L-arginine combined with a garlic extract, with neither the participants nor researchers knowing which treatment is given until the study ends. The garlic extract contains a standardised compound thought to improve blood flow and reduce inflammation, and the study will compare migraine frequency, pain severity, and quality of life between the two groups. We hypothesise that the combination of L-arginine and garlic extract will be more effective at preventing migraines than L-arginine alone.The trial will be conducted in two phases over 16 weeks. In the initial 8-week open-label phase, all participants will receive L-arginine. In the subsequent 8-week double-blind phase, participants will have been randomised in a 1:1 ratio to receive either L-arginine with placebo, or L-arginine with GE. Both participants and investigators will remain blinded to group allocation during this second phase. The primary outcome measures will be: 1) a short-form McGill pain questionnaire administered every 2 weeks, which assesses the occurrence and characteristics of migraine episodes, along with a visual analogue scale of average pain intensity; and 2) a migraine-specific quality-of-life questionnaire administered every 4 weeks, which evaluates the extent to which migraines interfere with aspects of daily living. The secondary outcomes will be: 1) blood levels of nitrite as a vasodilation biomarker; and 2) blood levels of asymmetric dimethylarginine (ADMA) and endothelin 1 (ET-1) as biomarkers of vasoconstriction; also, 3) an unexpected-effects questionnaire every 4 weeks, to assess positive, negative and/or neutral unexpected affects the participant would attribute to this treatment.