What Role Does Potassium Play in Exercise Performance?

May 12, 2019

by Cathe Friedrich

Potassium deficiency – do you get enough potassium in your diet? If you eat a processed or junk food diet, probably not. Potassium is the yen to sodium’s yang, as these two minerals help to balance one another. Potassium is an electrolyte, a mineral that forms a charged particle when dissolved in water. Along with sodium, bicarbonate, calcium, magnesium, chloride, and phosphate, these aptly named electrolytes play a vital function in maintaining life. In fact, you need electrolytes on a minute-by-minute basis to maintain life. For example, potassium plays a key role in fluid balance, nutrient entry into cells, nerve conduction, and muscle contraction. Since you need potassium for orderly muscle contraction, it helps regulate the heartbeat too.

One of the ways potassium participates in nerve conduction and muscle contraction is by its role in the sodium-potassium pump. This is a pump that helps regulate fluid balance, nutrient intake into cells, and maintain an electrical difference across cells that enables nerve cells to contract. The sodium-potassium pump ensures that more potassium is stored inside the cell and more sodium is stored outside. Sodium-potassium pumps are so active that they account for almost one-third of resting energy expenditure. That’s how important sodium and potassium balance is!

How Much Potassium Do You Need in Your Diet?

You need, at a minimum, 4,700 milligrams of potassium daily and some sources believe we need up to 6,000 milligrams daily, especially since studies link a diet higher in potassium with a lower risk of stroke. Potassium also plays a key role in regulating blood pressure. It does this by controlling how arteries, vessels that carry blood away from the heart to tissues, relax or dilate. Some studies show that consuming more potassium can lower blood pressure by as much as 5 mmHg. The downside is research suggests that about half of Americans don’t get enough dietary potassium.

Severe potassium deficiency is life-threatening. Being significantly low in potassium can cause an irregular heartbeat that leads to death. Low potassium can also lead to heart failure, where the heart muscle weakens and fluid builds up in the lungs or in the tissue of the body. But this is an extreme case of potassium deficiency that typically happens when people are taking diuretics that lower potassium or have a condition like bulimia where they lose potassium from frequent vomiting. Persistent diarrhea can also deplete potassium enough to cause health issues. Lesser, but less catastrophic degrees of potassium deficiency are more common.

Are You More at Risk of Potassium Deficiency When You Exercise?

If you go out and do a long, tough work, especially if it’s hot outside, you lose sodium, potassium, and chloride through sweating. That’s why experts recommend drinking an electrolyte-rich beverage to replace electrolytes if your workout will be longer than 60 to 90 minutes. Studies also show that after an intense exercise session, more potassium ends up outside cells than inside. During rapid muscle contractions, muscle cells also release more calcium to the outside of the cell. Such an imbalance may be enough to trigger leg cramps.

The theory as to why leg cramps happen is that disruption of the sodium-potassium pump makes it harder for calcium to enter cells. This, in turn, may trigger leg cramps. However, this is only a theory about what causes exercise-induced leg cramps. Another theory is that either dehydration or loss of electrolytes, including potassium, sensitizes nerve endings, and causes them to misfire. It is possible that there are multiple causes of exercise-associated leg cramps.

Potassium Deficiency: How to Get Enough Potassium in Your Diet

The Western diet is low in potassium but contains substantial amounts of sodium. The reason? Highly processed foods are naturally low in potassium but contain added sodium to enhance their flavor. One of the best sources of potassium is fruits and vegetables. But unless you’re getting 5 + servings of fruits and vegetables daily, which most people are, you’re at risk of a potassium shortfall. One of the best ways to ensure you are getting enough potassium is to eat more fruits and vegetables. Also, add a slice of avocado to your salad. It’s one of the highest potassium fruits and the healthy fats will help you absorb more of the fat-soluble nutrients, like beta-carotene, from the salad.

Also, make sure you’re replenishing electrolytes when you exercise. You already know that hydration is important, but for long periods of exercise, you also need to replace lost electrolytes, especially if you’re exercising in a hot environment.

Why You Shouldn’t Use Supplemental Potassium

You should be able to get sufficient potassium in your diet by eating whole foods, including lots of plant-based foods. Normally, your kidneys flush out any excess potassium from your body, but if your kidneys aren’t functioning normally, it can build up. For example, diabetics often have modestly reduced kidney function and may not be aware of it. Too much potassium is just as problematic as too little.

Also, some diuretics used to treat blood pressure have a potassium-sparing component to help prevent loss of potassium. If you take supplemental potassium with a potassium-sparing diuretic, your level could rise too high. Only take a potassium supplement if your physician recommends it. Because of the dangers of too much potassium, the amount of potassium legally allowed in potassium supplements is low. If you take a high-dose potassium supplement, you could get a spike in potassium that could be dangerous. Such a spike could cause an irregularity in heartbeat. However, when you get potassium from food, the fiber in the food slows absorption and prevents dangerous spikes.

The Bottom Line

Make sure you’re meeting your body’s potassium needs. If you’re not, you’re at higher risk of leg cramps and, potentially, changes in blood pressure and heart rate. The best way to avoid potassium deficiency is to eat fruits and vegetables. So add another serving of colorful vegetables to your plate and enjoy a fresh, piece of fruit!

References:

· J Physiol. 1990 Feb; 421: 105–122.

· J Mol Cell Cardiol. 1995 Apr;27(4):941-9.

· U.S. Department of Agriculture. “Potassium Intake of the U.S. Population”

· Sports Health. 2010 Jul; 2(4): 279–283.