Current issues of ACP Journal Club are published in Annals of Internal Medicine


Therapeutics

Increased dietary potassium led to stepwise reductions in antihypertensive medication in patients with well-controlled hypertension

ACP J Club. 1992 Mar-April;116:37. doi:10.7326/ACPJC-1992-116-2-037


Source Citation

Siani A, Strazzullo P, Giacco A, et al. Increasing the dietary potassium intake reduces the need for antihypertensive medication. Ann Intern Med. 1991 Nov 15;115:753-9.


Abstract

Objective

To evaluate the feasibility of reducing the need for medication in patients with pharmacologically controlled primary hypertension through increased dietary potassium intake.

Design

Randomized controlled trial of 1 year duration.

Setting

Hypertension outpatient clinic of a university hospital in Naples, Italy.

Patients

Eligibility criteria were age between 30 and 65 years; blood pressure (BP) < 160/95 mm Hg on antihypertensive medication at the last 2 clinic visits; and no secondary hypertension, renal failure, ischemic heart or brain disease, use of contraceptives, poor compliance with the medication regimen, or condition that required a special diet. The 1-year analysis included 47 of 54 randomized patients (87%).

Intervention

After a 1-month run-in period, eligible patients were randomized to high potassium (K) dietary intervention (n = 28) or customary diet (control, n = 26). The K group was asked to consume 3 to 6 portions of fruits or vegetables (each containing 10 to 12 mmol potassium) per day. These patients and the control group had monthly examinations and dietary monitoring. BP medication was reduced progressively in a standardized order. If BP increased, then medication was increased in the same steps as it had been reduced.

Main outcome measure

Reduction of antihypertensive medication at the end of 1 year.

Main results

The K group increased dietary potassium consumption by 68% and urinary potassium excretion by 45%. There were no significant changes in these measures for the control group. The groups did not differ in other dietary or biochemical findings. At the end of 1 year fewer pills were prescribed per day (P = 0.02), and a lower percentage of baseline medications was consumed by the K group than by the control group (24% vs 60%, P < 0.001). 38% of the K group compared with 9% of the control group needed no antihypertensive medication {95% CI for a difference of 25%, 3% to 47%},* and 81% of the K group compared with 29% of the control group needed less than half of their baseline medication for BP control {CI for a difference of 52%, 28% to 77%}*.

Conclusion

Increased dietary potassium led to stepwise reductions in antihypertensive medication in patients with well-controlled hypertension.

Source of funding: Not stated.

Address for article reprint: Dr. P. Strazzullo, Institute of Internal Medicine and Metabolic Diseases, 2nd Medical School, University of Naples, Via S. Pansini 5-80131, Naples, Italy.

*Numbers calculated from data in article.


Commentary

This study is remarkable for effecting a year-long 45% increase in potassium excretion (a direct measure of intake) in patients assigned to a high potassium diet. Whether increased potassium consumption could be accomplished in a North American population and have similar effects on BP is uncertain. Because fruit and vegetable intakes are higher in the usual Mediterranean diet than in the North American diet, this may make the former more amenable to this change. Hypertension trials using a low sodium/high potassium regimen in the United States have been unable to achieve similar dietary potassium increases.

A recent meta-analysis of potassium supplementation showed a significant mean reduction in systolic pressure of 5.9 mm Hg (1). Although the end points differ, these 2 reports show antihypertensive effects of increased potassium intake through diet or supplementation. Synergism with specific medications may be important in light of the hypokalemic effects of most diuretics.

The 40% reduction in antihypertensive medication requirements of the control group after 1 year (with 9% of patients medication-free) may indicate that study participation improved medication compliance and showed the tendency of initially high BP to regress toward normal over time. In the Hypertension Control Program, after cessation of antihypertensive medication, 50% of patients were normotensive at 1 year, but only 5% remained medication-free after 4 years (2).

It is difficult to change 1 component of a diet without altering the nutrient profile. Although only potassium and fiber intake increased significantly in this small sample, total fat intake decreased and mineral intake increased, which may have had a beneficial effect on BP.

The evidence from this study supports a high-potassium diet as an adjunctive treatment for hypertension.

Cynthia D. Morris, PhD, MPH
Oregon Health Sciences UniversityPortland, Oregon, USA

Cynthia D. Morris, PhD, MPH
Oregon Health Sciences University
Portland, Oregon, USA


References

1. Cappuccio FP, MacGregor GA. Does potassium supplementation lower blood pressure? A meta-analysis of published trials. J Hypertens. 1991;9:465-73.

2. Stamler R, Stamler J, Grimm R, et al. Nutritional therapy for high blood pressure. JAMA. 1987;257:1484-91.