Electrolyte intake and blood pressure: a study in contradictions and controversy

The widely accepted recommendation that hypertensive subjects benefit from a reduction of sodium intake has lately been challenged by a number of publications. From one analysis of the First National Health and Nutrition Examination Survey (NHANES) in the USA, the conclusion was reached that hypertension was associated more frequently with low nutritional sodium intake and low calcium intake. Other authors analysing the same data but using different criteria and statistical methods did not confirm such conclusions. The criticisms of epidemiological data concerning the relationship between salt intake and hypertension include frequently inconsistent definition of hypertension, failure to consider methodological uncertainties in the measurement of salt intake and excretion and inadequate control of confounding variables such as age, race, sex, body mass index and lifestyle. The claimed link between nutritional calcium and blood pressure is completely unclear and needs careful investigation. A reduction of sodium intake from the present day excessive amounts to moderate intakes of 3-6 g per day is still recommended in order to prevent the establishment of high blood pressure, to reduce hypertensive blood pressure levels or to reduce the doses of antihypertensive drugs. With mild hypertension being the main problem of high blood pressure management, further research is necessary to place dietary intervention in the non-pharmacological treatment of hypertension on a firmer, more rational footing.