Q: My blood pressure runs a bit high. I am trying to lower it without medication. I have decreased my salt intake, but what about potassium?
A: When it comes to fighting high blood pressure, the average American diet delivers too much sodium and too little potassium. Eating to reverse this imbalance could prevent or control high blood pressure and translate into fewer heart attacks, strokes, and deaths from heart disease.
Normal body levels of potassium are important for muscle function. Potassium relaxes the walls of the blood vessels, lowering blood pressure and protecting against muscle cramping. A number of studies have shown an association between low potassium intake and increased blood pressure and higher risk of stroke. On the flip side, people who already have high blood pressure can significantly lower their systolic (top number) blood pressure by increasing their potassium intake when they choose to eat healthy foods.
Most Americans get barely half of the recommended amount of potassium -- 4,700 milligrams (mg) a day. Fruits, vegetables, beans, and some seeds offer good ways to get more of it. Bananas (about 425 mg of potassium in a medium-sized one) are often held up as the poster child for potassium, but there are better sources.
Since people with high blood pressure may also be trying to lose weight, consider potassium rich foods that are low in calories and carbohydrates. Good examples include broccoli, water chestnuts, spinach, and other leafy greens. Also good -- although slightly higher in carbs and calories -- are butternut squash and sweet potatoes, and fruits such as cantaloupe, kiwi, and nectarines.
Normally the kidneys do a great job of getting rid of any extra potassium we ingest. However, people with advanced kidney disease have impaired ability to excrete potassium. So, eating a potassium-rich diet could lead to dangerously high blood levels of the chemical. Your doctor or dietician will give you specific instructions about foods you should limit.
Although potassium rich diets are generally healthy, the same doesn't always go for supplements. It's safest to only take a potassium supplement if it your doctor recommends it. That's especially true if you take certain medications that interfere with the potassium regulation by the kidneys. Examples include spironolactone (Aldactone), amiloride, eplerenone (Inspra) or triamterene. Drugs used for hypertension like angiotensin converting enzyme (ACE) inhibitors and angiotensin blockers (ARBs) and high dose NSAIDs such as ibuprofen and naproxen also can increase blood potassium levels when combined with supplements.
(Howard LeWine, M.D., is an internist at Brigham and Women's Hospital in Boston and assistant professor at Harvard Medical School. For additional consumer health information, please visit www.health.harvard.edu.)