Gotshall 2000.

Methods	Randomised placebo‐controlled cross‐over study.
Participants	8 (1 male and 7 female) participants with objectively diagnosed exercise‐induced asthma (> 10% drop in FEV1 after exercise). Mean age 23 years. All subjects used short‐acting rescue medications and none were on maintenance medications. Control group were 8 (4 male and 4 female) non‐asthmatics. Exclusion criteria: no participants had atopic asthma.
Interventions	All participants entered the study on their normal sodium diet for 1 week. Participants then consumed a low sodium diet (65 mmol of sodium a day by means of a meal plan) and randomly assigned to either high sodium limb or low sodium limb for 2 weeks. Thereafter, a 1‐week wash‐out period on a normal sodium diet followed, then all patients followed alternative diet for 2 weeks (crossover). In the low sodium limb participants consumed a low sodium diet and placebo tablets and participants in the high sodium limb consumed a low sodium diet (174 mmol of sodium/day).
Outcomes	FEV1, FVC, FEV1/FVC and PEFR pre‐exercise test and 1,5,10,15 minutes post‐exercise tests.
Notes	Author reply received (03/02/01) further information provided on allocation (drawing lots)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Allocation of treatment was done by drawing lots.
Allocation concealment (selection bias)	Low risk	Treatments were drawn by lots so both participants and investigators blinded to the randomisation sequence.
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Described as blinded; no other information available.
Incomplete outcome data (attrition bias) All outcomes	Low risk
Selective reporting (reporting bias)	Unclear risk	Not clear from information presented.
Other bias	Unclear risk	Population recruited from an university population only. No calculation of power described.