1. Details of included studies.

Study	Number of Participants	Initial Diet Requirements	Interventions		Intervention period
			Low sodium diet	High sodium diet
Asthma studies
Burney 1989	36	Low sodium diet	Low sodium diet and placebo tablets	Low sodium diet and 80 mmol of sodium a day	Cross‐over  2 weeks each limb
Lieberman 1992	17	Low sodium diet used for hypertension	Low sodium diet	Add sodium to diet and consuming 34 mmol of sodium a day	Cross‐over 2 weeks each limb
Carey 1993	27	Low sodium diet aiming for 80 mmol of sodium a day	Low sodium diet and placebo tablets	Low sodium diet and 200 mmol of sodium a day	Cross‐over 5 weeks each limb
Medici 1993	18	Low sodium diet aiming for 86 to 103 mmol of sodium a day	Low sodium diet and placebo tablets	Low sodium diet and 154 mmol of sodium a day	Cross‐over 3 weeks each limb
Pogson 2008	220	Low sodium diet aiming for 80 mmol of sodium a day	Low sodium diet and placebo tablets	Low sodium diet and 80 mmol of sodium a day	Parallel group 6 weeks intervention period
Exercise‐ induced asthma studies
Mickleborough 2000	15	Meal plan aiming for 65 mmol of sodium a day	Low sodium diet and placebo tablets	Low sodium diet and 174 mmol of sodium a day	Cross‐over 2 weeks each limb
Mickleborough 2001b	16	Meal plan aiming for 65 mmol of sodium a day	Low sodium diet and placebo tablets	Low sodium diet and 174 mmol of sodium a day (sodium bicarbonate)	Cross‐over 2 weeks each limb
Gotshall 2000	8	Meal plan aiming for 65 mmol of sodium a day	Low sodium diet and placebo tablets	Low sodium diet and 174 mmol of sodium a day	Cross‐over 2 weeks each limb
Mickleborough 2005	24	Meal plan aiming for 65 mmol of sodium a day	Low sodium diet and placebo tablets	Low sodium diet and 174 mmol of sodium a day	Cross‐over 2 weeks each limb