1. Study design of the eleven included trials.

Study	Number/design/clinical Setting	Mean age (years)	% Female	Magnesium dose and route of administration	Frequency of administration	Treatment and assessment periods (days)	Washout period (days)	Comparator
Cohen‐Hagai 2018	N = 29 Parallel Liver cirrhosis	62.0	41.4%	520 mg magnesium oxide tablets (315 mg elemental Mg)	Once daily	Treatment 56 Assessment 56	Not applicable	Matched placebo tablet
Dahle 1995	N = 73 Parallel Pregnancy	Not given (child‐ bearing years)	100%	5 mmol combination Mg lactate + Mg citrate (122 mg elemental Mg) taken orally	Once each morning and twice each evening	Treatment 21 Assessment 21	Not applicable	Matched placebo tablet
Frusso 1999	N = 45 Cross‐over Idiopathic	61.6	73.3%	Mg citrate 900 mg tablet (100 mg elemental Mg) taken orally	Twice daily	Treatment 28 Assessment 28	28	Matched placebo tablet
Garrison 2011a	N = 46 Parallel Idiopathic	69.3	69.6%	20 mmol Mg sulphate (486 mg elemental Mg) given intravenously	Once daily over 4 hrs on 5 consecutive days	Treatment 5 Assessment 90	Not applicable	Matched placebo solution
Nygaard 2008	N = 45 Parallel Pregnancy	30.9	100%	Mg lactate and Mg citrate chewable tablets containing 122 mg elemental Mg taken orally	Once each morning and twice each evening	Treatment 14 Assessment 14	Not applicable	Matched placebo tablet
Roffe 2002	N = 73 Cross‐over Idiopathic	62.9	54.3%	1830 mg of tri‐magnesium dicitrate powder (300 mg elemental Mg) poured from a sachet into a glass of water taken orally	Once each evening	Treatment 42 Assessment during last 28 days of treatment	First 14 days of second treatment period considered as washout	Matched placebo powder
NCT00963638	N = 40 Parallel Idiopathic	66.6	57.5%	Slow release tablet of Mg lactate containing 84 mg of elemental Mg taken orally	2 tablets twice daily	Treatment 30 Assessment 30	Not applicable	Matched placebo tablet
Sohrabvand 2006	N = 84 Parallel Pregnancy	Not given (child‐ bearing years)	100%	7.5 mmol magnesium aspartate (182 mg elemental Mg) taken orally. Unclear if tablet or powder / solution	Twice daily	Treatment 14 Assessment 28	Not applicable	3 different comparators 1) No treatment 2) 500 mg calcium carbonate tablet once daily 3)100 mg of thiamine (vit B₁) plus 40 mg of pyridoxine (vit B₆) once daily
Shahraki 2006	N = 120 Parallel Pregnancy	29.2	100%	8 cc of an 8% milk of magnesium suspension (267.2 mg of elemental magnesium)	3 times a day	Treatment 45 Assessment 90	Not applicable	2 different comparators 1) 100 mg of vitamin E once daily 2) 500 mg of calcium carbonate once daily
Supakatisant 2015	N = 86 Parallel Pregnancy	28.7	100%	Mg bisglycinate tablets containing 100 mg of elemental mg taken orally	3 times a day	Treatment 28 Assessment 28	Not applicable	Matched placebo tablets
Roguin Maor 2017	N = 94 Parallel Idiopathic	64.9	63%	865 mg magnesium oxide capsules (520 mg elemental Mg)	Once daily at bedtime	Treatment 28 Assessment 28	Not applicable	Matched placebo capsules

vit B₁: vitamin B₁