Should I take a potassium supplement?

DEAR DOCTOR K:

I have high blood pressure. Should I take a potassium supplement?

DEAR READER:

This is a great question, but before I answer, let me take a step back to explain the connection between potassium and blood pressure.

Tens of thousands of years ago, our ancestors survived on wild animals and a variety of plant foods. This diet delivered plenty of potassium but scant sodium. Today, the average American diet contains about twice as much sodium as potassium, as a result of the high levels of salt in processed foods. This sodium-potassium imbalance is thought to be a major contributor to high blood pressure.

Now, back to your question. The short answer is no, you should not take potassium supplements unless your doctor prescribes them. People on blood pressure medications, in particular, need to be careful about potassium supplements.

Many blood pressure medications can lower your potassium level. Very low potassium can lead to dangerous heart rhythms. Many commonly prescribed diuretics lower potassium levels. If you are taking potassium-lowering diuretics, your doctor will check the level of potassium in your blood. If it is low, the doctor may prescribe potassium supplements.

But other types of diuretics, and other commonly prescribed blood pressure medicines, can raise potassium levels. Examples of such drugs are the diuretic called spironolactone, the drugs called ACE inhibitors, and drugs called angiotensin receptor blockers (ARBs). Common painkillers such as ibuprofen (Advil, Motrin) or naproxen (Aleve) can raise potassium levels. Abnormally high potassium levels also can cause dangerous heart rhythms.

If you are taking any medicines known to either raise or lower your potassium to dangerous levels, your doctor should periodically check your blood potassium level. Keeping that level in the correct range is important. This mineral also plays a key role in the function of nerves and muscles, including heart muscle.

Your kidneys help regulate potassium levels in your blood. They tend to keep your potassium level from going abnormally high or low. But age and medical conditions may impair kidney function. As a result, the kidneys are not as good at protecting you against abnormal potassium levels.

The FDA limits over-the-counter potassium supplements to less than 100 milligrams (mg). However, grocery stores carry salt substitutes that may contain much higher amounts of potassium. People trying to curb their sodium intake may use salt substitutes. That’s a bad idea if you take a blood pressure medicine that tends to raise potassium levels.

Your best bet is to get your potassium from foods instead of pills. Many fruits and vegetables are rich in potassium. Spinach, sweet potatoes, cantaloupe, bananas and avocado are all good sources. Potassium-rich diets help control blood pressure and also lower your risk of stroke.

Another connection between potassium and high blood pressure is a rare condition of the adrenal glands that can cause both high blood pressure and very low blood potassium levels.

So if you have high blood pressure, ask your doctor what your potassium level is. If the doctor hasn’t checked your potassium, gently suggest that it might be a good idea.