Last updated: Aug 15, 2016

You probably know bananas are loaded with potassium, but you may not realize the vital role this mineral plays in the body. Potassium aids in muscle contraction, fluid regulation, and mineral balance. What's more, potassium blunts the effects of excessive sodium consumption—a problem most Americans have. The average U.S. adult takes in 3,400 milligrams of salt per day, nearly 50% more than the recommended upper limit of 2,300 milligrams. A potassium-rich diet helps the body flush out sodium. It also helps relax blood vessel walls and, in turn, lower blood pressure. Increasing your potassium intake while reducing your sodium intake can slash your stroke risk by 21%, and may also lower your odds of heart disease, according to a 2011 study published in the Journal of the American College of Cardiology.

If you eat lots of foods that come in a bag or box, then you're almost surely low on potassium, says Lauren Blake, RD, a dietitian at The Ohio State University Wexner Medical Center. Upping your intake of whole fruits and vegetables will help you hit the expert-recommended 4,700 milligrams of potassium a day; try these 15 potassium-rich foods. You should also check in with your doctor if you suspect you need more potassium. Here are the biggest signs you're running low:

You're always tired

If you can’t seem to rest enough and your energy levels are low, you may be potassium deficient, says Blake. “Every cell in your body needs the right amount of potassium to function,” she explains. “If you are increasingly exhausted and know you are getting enough sleep, potassium might be the cause.” (That said, other issues with your diet, stress, or sleep deprivation can also leave you feeling chronically sluggish, so you shouldn't assume a potassium deficiency is the culprit.)

RELATED: 14 Reasons You're Always Tired

You have muscle weakness or cramping

Potassium plays a key role in smooth muscle contraction, both in the heart and across the entire body. So when levels are low, you might experience “aches and spasms” throughout the day or while exercising, says Blake.

You feel faint, dizzy, or tingly

Potassium can wax and wane throughout the day, and a large drop can slow your heartbeat, making you feel like you’re going to pass out. “This is not common, and many other factors can be the cause, but it’s important to see your doctor if you experience this,” Blake says. Tingling arms or legs is another signal you shouldn't ignore.

You have high blood pressure or palpitations

Without enough potassium, blood vessel walls can become constricted, which results in hypertension, says Blake. Also watch out for heart palpitations; the heart muscle has more difficulty pumping when the sodium-potassium balance is out of whack.

RELATED: 20 Ways to Lower Your Blood Pressure Naturally

You're bloated all the time

When you're low on potassium, your body struggles to regulate its sodium levels, and can cause salt-induced bloating.