OBJECTIVE

To provide updated, evidence-based recommendations on the consumption, through diet, and supplementation of the cations potassium, magnesium and calcium for the prevention and treatment of hypertension in otherwise healthy adults (except pregnant women).

OPTIONS

Dietary supplementation with cations has been suggested as an alternative or adjunctive therapy to antihypertensive medications. Other options include other nonpharmacologic treatments for hypertension.

OUTCOMES

The health outcomes considered were changes in blood pressure and in morbidity and mortality rates. Because of insufficient evidence, no economic outcomes were considered.

EVIDENCE

A MEDLINE search was conducted for the period 1966-1996 with the terms hypertension and potassium, magnesium and calcium. Reports of trials, meta-analyses and review articles were obtained. Other relevant evidence was obtained from the reference lists of articles identified, from the personal files of the authors and through contacts with experts. The articles were reviewed, classified according to study design, and graded according to the level of evidence.

VALUES

A high value was placed on the avoidance of cardiovascular morbidity and premature death caused by untreated hypertension.

BENEFITS, HARMS AND COSTS: The weight of the evidence from randomized controlled trials indicates that increasing intake of or supplementing the diet with potassium, magnesium or calcium is not associated with prevention of hypertension, nor is it effective in reducing high blood pressure. Potassium supplementation may be effective in reducing blood pressure in patients with hypokalemia during diuretic therapy.

RECOMMENDATIONS

For the prevention of hypertension, the following recommendations are made: (1) The daily dietary intake of potassium should be 60 mmol or more, because this level of intake has been associated with a reduced risk of stroke-related mortality. (2) For normotensive people obtaining on average 60 mmol of potassium daily through dietary intake, potassium supplementation is not recommended as a means of preventing an increase in blood pressure. (3) For normotensive people, magnesium supplementation is not recommended as a means of preventing an increase in blood pressure. (4) For normotensive people, calcium supplementation above the recommended daily intake is not recommended as a means of preventing an increase in blood pressure. For the treatment of hypertension, the following recommendations are made. (5) Potassium supplementation above the recommended daily dietary intake of 60 mmol is not recommended as a treatment for hypertension. (6) Magnesium supplementation is not recommended as a treatment for hypertension. (7) Calcium supplementation above the recommended daily dietary intake is not recommended as a treatment for hypertension.

VALIDATION

These guidelines are consistent with the results of meta-analyses and recommendations made by other organizations. They have not been clinically tested.

SPONSORS

The Canadian Hypertension Society, the Canadian Coalition for High Blood Pressure Prevention and Control, the Laboratory Centre for Disease Control at Health Canada, and the Heart and Stroke Foundation of Canada.