Study methods flawed

EDITOR, - In their paper on the effect of a reduced sodium and increased potassium and magnesium intake on blood pressure J M Geleijnse and colleagues do not adequately deal with several methodological issues which could potentially confound their findings.1

Firstly, the authors reported that, when asked to identify the mineral salt diet after the trial, 72% of the intervention group correctly did so because of the taste. This raises the question of the effectiveness of the blinding process. This is important because it could have influenced the subjects' reaction to the trial and therefore their blood pressure, as it is common knowledge that a low salt diet reduces blood pressure.

Secondly, the study did not have a long lead in period, suggesting that normotensive subjects could have been …