Does a high potassium/low sodium diet reduce hypertension?
WILLIAM IVERSON, MD
11/8/96
CASE SCENARIO:
A 50 year old man presents to your clinic for a routine visit and is found to have a BP of167.90. Upon review of the chart you see that he has had other BPsthat have also been mildly elevated.
CLINICAL BOTTOM LINES:
1. Substituting common table salt (NaCl) with mineral salt high in potassium, magnesium and low in sodium lowered blood pressure in elderly patients with mild hypertension.
2. The diet in the trial and the mineral salt were very palatable and well accepted by the participants.
3.In the initial management of hypertension it may be easier and more effective to get patients to use some type of mineral salt than to get them to restrict salt intake or to use a pure potassium chloride salt substitute.
THE EVIDENCE:
Double-blinded, randomized controlled trial of 100 patients
age 55-75 years old with mild to moderate untreated hypertension
(SBP 140-200 mm Hg or DBP 85-l 10 mm Hg). Patients were
randomized to receive a mineral salt (Na:K:Mg, 8:6:1 ) for use at
the table and in prepared foods or simple table salt (NaCI).
| Week 0 | Week 8 | Week 16 1 | Week 242 | Intervention3 | |
| Systolic blood pressure (mm Hg): | |||||
| Controls | 157.6 (2.0) | 161.0 (2.1) | 160.0 (2.2) | 156.0 (1.9) | 158.5 (1.8) |
| Mineral salt group | 157.9 (2.0) | 151.8 (2.1) | 152.6 (2.2) | 150.9 (1.9) | 151.7 (1.8) |
| Difference (95% confidence interval) 4 | -9.7 (-13.6 to -5.7) P<0.001 | -8.7 (-13.0 to -4.5) P<0.001 | -7.7 (-12.3 to -3.1) P=0.001 | -8.7 (-12.2 to -5.2) P<0.001 | |
| Diastolic blood pressure (mm Hg): | |||||
| Controls | 91.0 (1.3) | 92.7 (1.4) | 92.3 (1.4) | 90.9 (1.2) | 92.1 (1.2) |
| Mineral salt group | 89.7 (1.3) | 87.0 (1.4) | 86.7 (1.4) | 86.8 (1.2) | 86.9 (1.2) |
| Difference (95% confidence interval) | -4.2 (-7.0 to -1.4) P=0.004 | -4.0 (-7.1 to -0.9) P=0.01 | -2.8 (-5.8 to 0.2) P=0.06 | -3.6 (-6.0 to -1.1) P=0.05 | |
1 Values for week 16 were missing for one control
and one subject in mineral salt group.
2 Values for week 24 were missing for two controls and
one subject in mineral salt group.
3 Mean of measurements at weeks 8, 16, and 24.
4. Difference in change from baseline between study
groups.
COMMENTS:
1. Hypertension is common among the elderly and is known risk
factor for heart disease and stroke.
2. Diet effects blood pressure and changes in diet are still first line therapy in reducing hypertension.
3. Several other studies have looked at the individual BP lowering effects of increased magnesium and potassium and decreased sodium in the diet and the BP effect in this study was greater than those estimates. This may be do to the simultaneous alteration of all these minerals, the age of the study population, the unique characteristics of this mined salt or a combination of these factors.
4. Despite the good internal validity of this study it has uncertain or poor generalizability to our patient population.
5. This study suggests that further investigation into dietary effects on BP is still very warranted.
REFERENCE: Geleijnse JM, Witteman JC, Bak AA,
den Breeijen JH, Grobbee DE. Reduction in blood pressure with a
low sodium, high potassium, high magnesium salt in older subjects
with mild to moderate hypertension. BMJ.Aug 13,1994; 309: 436-40