Hilary Green 2000

Methods	Double‐blind, randomised, controlled cross‐over study The trial was conducted in New Zealand
Participants	38 healthy volunteers. Age: over 40 years
Interventions	Intervention: high‐calcium skim powder milk. Control: replacement of usual liquid milk with 2 servings a day of skim non‐fortified powder milk. Trial duration: 4 weeks, with a minimum of 4 weeks of wash‐out between interventions.
Outcomes	Systolic blood pressure and ambulatory blood pressure
Notes	"For many people in the trial, the control skim milk provided additional calcium to the diet. This may explain the small reduction in office".. standing systolic blood pressure observed in the control group. Calcium intake was calculated using 24 hour food recalls. This study was supported by The New Zealand Dairy Board.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not described
Allocation concealment (selection bias)	Unclear risk	Not described
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Stated "Randomized double‐blind controlled trial'. Double‐blind, randomised, controlled cross‐over study. "Each volunteer consumed each of the milks in randomised order." "The milk was provided to the volunteers as a dry powder."
Blinding of outcome assessment (detection bias) All outcomes	Low risk	"Ambulatory blood pressure monitor. Automated oscillometric blood pressure monitor (A&D, Model UA‐751; A&D Medical Division, Milpitas, California, USA)."
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Dropouts not reported
Selective reporting (reporting bias)	Low risk	All primary outcomes were reported.
Other bias	High risk	There were small differences (in different directions) between intervention and placebo participants in baseline office and ambulatory blood pressure, except for baseline systolic blood pressure: Skim milk 121 ± 14 and high‐calcium skim milk 125 ± 19. Controls may have accidentally received a calcium boost from the placebo milk that should be treated as a potential bias.