Potassium and Hypertension
Many epidemiologic and intervention studies have shown that potassium intake is associated with a blood pressure lowering effect.1,2 In fact, in October 2000, the U.S. Food and Drug Administration (FDA) acknowledged this effect when it authorized a new health claim that, "Diets containing foods that are good sources of potassium and low in sodium may reduce the risk of high blood pressure and stroke."
Recent meta-analyses of the results of over 30 trials have provided evidence for an inverse relationship between oral potassium supplementation and hypertension.2 The reduction in blood pressure is generally greater in hypertensive individuals than in normal individuals and affects both diastolic and systolic blood pressure. Subjects with the highest sodium intake are most likely to experience a drop in blood pressure when potassium intake is increased.
Hypertension is a risk factor for several chronic diseases including coronary artery disease, stroke and congestive heart failure. Almost half of individuals over the age of 55 in most industrialized countries have high blood pressure.1
Experts have suggested that increased potassium intake should be considered as part of the treatment of hypertension.4 The majority of studies showing a beneficial effect of potassium involved administering potassium in a pill form as a chloride salt (rather than potassium-rich foods). However, there is no reason to suggest that the beneficial effects observed with potassium supplements would be any different if dietary sources provided the potassium. In fact, it has been proposed that it would be unfavorable to recommend potassium supplements to hypertensive subjects and the population at large because of potential adverse effects.4 Thus, it has been recommended that potassium from dietary sources be encouraged rather than potassium supplementation.
The recently published Dietary Approaches to Stop Hypertension (DASH) trial showed that a diet high in fruits and vegetables, and consequently potassium, was associated with reduced blood pressure.5 The DASH study design included other dietary changes; potassium intake may not have been the only dietary variable responsible for the positive outcome, but was likely an important factor.
The average daily intake of potassium in the United States varies between 1200 and 4000 milligrams per day.6 The current recommended intake for potassium is 2000 milligrams per day. However, based on the results of recent research it has been proposed that an average daily intake of 3000 milligrams per day might be a more appropriate minimum (based on a recommended 40 milligrams per kilogram of body weight).1
Many fruits and vegetables, bananas in particular, are excellent food sources of potassium and a diet rich in these foods can provide a significant amount of potassium each day. An average sized banana (120 grams) contains 475 milligrams of potassium, providing almost 24% of the current recommended intake and 16% of the proposed recommendation of 3000 milligrams.
In summary, several lines of evidence suggest that potassium intake is associated with reduced hypertension. The mechanism(s) accounting for the beneficial effect is unknown but is thought to be multifactorial. There have been no human trials in which dietary potassium was the sole intervention but dietary approaches that include a high potassium intake are associated with reduced blood pressure. Bananas are significant sources of potassium and would be expected to have a beneficial affect on blood pressure.
REFERENCES
1Luft F. Potassium and its regulation. In: Ziegler E, Filer L, eds. Present Knowledge in Nutrition. Seventh Edition ed. Washinton, DC: ILSI Press; 1996:272-276
2Whelton P, He J, Cutler J. Effects of oral potassium on blood pressure: meta-analysis of randomized controlled clinical trials. JAMA. 1997;277:1624-1632
3Fang J, Madhavan S, Alderman M. Dietary potassium and stroke mortality. Stroke 2000;2000(7):1532-1537
4Suter P. Potassium and hypertension. Nutr Rev. 1998;56(5 Pt 1):151-153
5Appel L, Moore T, Obarzanek E. A clinical trial of the effects of dietary patterns on blood pressure. New Eng J Med. 1997;336:117-1124.
6Young D, Lin H, McCabe R. Potassium's cardiovascular protective mechanism Am J Physiol. 1995;37:R825-R827
