How Does Potassium Affect High Blood Pressure?

Potassium's ability to lower blood pressure is often ignored

Bananas
melecis/iStock

Hypertension, (or abnormally high blood pressure) is one of the most commonly prevalent chronic diseases. It is therefore also a public-health problem. As per the Centers for Disease Control (CDC), prevalence of hypertension among U.S. adults aged 18 and over was as high as 29.1 percent in 2011–2012. Globally, the overall prevalence of raised blood pressure in adults aged 25 and over was around 40 percent in 2008.

Persistently high blood pressure has grave consequences, leading to an increased risk of stroke, heart attack, kidney failure, etc. Treatment of high blood pressure is an ever-evolving field, an endeavor that started about a century ago.

A Brief History of Hypertension

It is hard to imagine that the modern technique of measuring blood pressure has only been around for a little over 100 years (when Dr. Kortokoff, a Russian surgeon, described the method in a single paragraph). While we could then measure blood pressure, no one really knew what a "normal" human blood pressure should be. Later, population-based studies were conducted to answer that question. With that knowledge came the realization that higher blood pressure could increase risk of heart and vascular disease.

Unfortunately, in the early 20th century, no good treatment existed for hypertension. Whatever little treatment strategies existed sound almost medieval and barbaric by today's standards.

These included bloodletting by phlebotomy, or even cutting out someone's kidneys to bring blood pressure down. In fact, severely elevated blood pressure was even referred to as malignant hypertension, the word malignant suggesting a prognosis as bad as cancer.

Modern Treatments for High Blood Pressure

Today, physicians no longer need to play vampire to treat their patients' high blood pressure.

This is partly due to our improved understanding of the physiology of human blood pressure and the impact of external factors like diet (which includes electrolytes like sodium, potassium, etc). Like many problems though, the more we learn, the more questions crop up.

So, the average person might make the mistake of thinking that the modern doctor has perfected the art and science of treating high blood pressure. Yet, even today, treatment of hypertension and how to approach the problem still remains a matter of intense research and debate. One only needs to look at multiple guidelines published by organizations around the world telling the average physician when and how to treat high blood pressure. Each claims to be the last word on the subject; that is, until the next guideline comes out. One of the common guidelines used in the U.S. by physicians for treating hypertension is something called the Joint National Committee (JNC) guidelines.

How Is Blood Pressure Regulated?

Before we understand the role of potassium in regulating blood pressure, it is important to have an overview of exactly how our body's "thermostat" for blood pressure works. This thermostat involves a complex coordination of mechanisms regulated by our nervous system, the kidneys, the endocrine system which makes hormones, the heart, our blood vessels, the amount of fluid running in the blood vessels, our electrolyte levels, and more.

For something that seems as trivial (as when you say, "my blood pressure runs 120/80"), it is fascinating to realize how this ultra-complex mechanism needs to be working in perfect coordination every second of our lives to keep our blood pressure running just where it should be.

Electrolytes and Hypertension: Potassium

When it comes to electrolytes and blood pressure, most physicians and even the average person usually understands the role of sodium. Patients are bombarded with messages about cutting their sodium intake, and rightfully so. Unfortunately, not enough emphasis is given during the course of a clinical discussion about the beneficial role of potassium on blood pressure.

As described here, potassium has an essential role in human physiology, and is an element necessary for life. Its levels are largely maintained by the kidneys. There are data that suggest that not eating enough potassium in our diet could lead to an increase in blood pressure, and even increase risk of kidney disease and stroke. There are also data from a meta-analysis which showed that a 1.6 gram increase in potassium intake per day could lower risk of stroke by as much as 21 percent. And if you worsen the situation by consuming a high amount of sodium as well, then effect on your blood pressure is even more exaggerated. It therefore seems that when it comes to our blood pressure, potassium is clearly the good guy.

Why Does Potassium Lower Blood Pressure?

We are not sure yet. However, this again is a subject of active research. One of the hypotheses that is being studied is potassium's impact on the kidneys' ability to get rid of sodium from the body. We do know that low blood levels of potassium from a low potassium diet could increase reabsorption of sodium in the kidney, and cause consequent hypertension.

Could Eating a High Potassium Diet Lower Blood Pressure?

While multiple trials were conducted to answer this question, a larger meta-analysis of 16 randomized trials has made it easier to interpret the data by crunching the numbers for us. We therefore have evidence to state that an increase in potassium intake could possibly lower blood pressure in patients who do suffer from hypertension. However, normal people with no high blood pressure issues might not see a similar reduction. There also seems to be a correlation between dose and effect, wherein people with the highest increase in potassium intake (of 90-120 mEq per day) could see a larger reduction in blood pressure.

High Potassium Diet Is Not for Everyone

Before you start gorging on bananas and tomatoes, please take a few minutes to discuss with your physician whether or not a high potassium diet might be right for you. There would be people for whom a high potassium diet might hurt more than it helps. These include people with advanced kidney disease, or people on certain kinds of blood pressure medications like angiotensin converting enzyme (ACE) inhibitors or spironolactone, where a high potassium diet could increase risk of dangerously high blood potassium levels/hyperkalemia. For the right patient though, a potassium rich diet might come with cardiovascular benefits, as the data above suggest.

Sources

Aburto NJ, Hanson S, Gutierrez H, et al. Effect of increased potassium intake on cardiovascular risk factors and disease: systematic review and meta-analyses. BMJ. 2013 Apr 3;346:f1378. doi: 10.1136/bmj.f1378.

Araki S, Haneda M, Koya D, et al. Urinary Potassium Excretion and Renal and Cardiovascular Complications in Patients with Type 2 Diabetes and Normal Renal Function. Clin J Am Soc Nephrol. 2015 Dec 7;10(12):2152-8. doi: 10.2215/CJN.00980115. Epub 2015 Nov 12.

D'Elia L, Barba G, Cappuccio FP, et al. Potassium intake, stroke, and cardiovascular disease a meta-analysis of prospective studies. J Am Coll Cardiol. 2011 Mar 8;57(10):1210-9. doi: 10.1016/j.jacc.2010.09.070.

James PA, Oparil S, Carter BL, et al. 2014 Evidence-Based Guideline for the Management of High Blood Pressure in Adults. Report From the Panel Members Appointed to the Eighth Joint National Committee (JNC 8). JAMA. 2014;311(5):507-520. doi:10.1001/jama.2013.284427

Yang Q, Liu T, Kuklina EV, et al. Sodium and potassium intake and mortality among US adults: prospective data from the Third National Health and Nutrition Examination Survey. Arch Intern Med. 2011 Jul 11;171(13):1183-91. doi: 10.1001/archinternmed.2011.257.

Continue Reading