You’ve heard many times that dairy is a good source of calcium, that bananas are rich in potassium, and that you should watch your sodium intake. You’ve also heard many times that one of the benefits of sports drinks and other nutritional products formulated for use during exercise is that they contain electrolytes, which the body loses through sweat. These electrolytes are the very same minerals—calcium, potassium, sodium, and a few others—found in the food we eat.
What Are Electrolytes?
As their name suggests, electrolytes are minerals that carry an electrical charge, which makes them good at transferring electricity in the body. Like other nutrients, they serve a variety of functions. Among the major electrolyte functions are regulating the balance of fluids in the body, facilitating muscle contractions, and controlling pH balance in tissues.
Also like other nutrients, electrolytes are needed in certain amounts for optimal health. Consuming either too little or too much of them leads to health problems. The most common electrolyte deficiency in the American diet is calcium. Men and women between the ages of 19 and 50 need about 1,000 mg of calcium per day. The average American adult gets only 750 mg per day. Women are especially likely to fall short. The best dietary sources of calcium are dairy products, greens, and tofu.
At the other extreme is sodium, which most people consume too much of. According to the FDA, the safe upper limit for sodium intake is 2,300 milligrams per day. The average American consumes 3,400 of sodium per day. High levels of sodium intake are believed to elevate blood pressure, or at least to exacerbate hypertension in individuals who already suffer from it. Eighty percent of the sodium in the American diet comes from salt added to processed foods such as canned soups, snack chips, and frozen dinners. Eating fewer of these foods is therefore the simplest way to reduce sodium intake.
To get the right amounts of the various electrolyte minerals in your diet, it is not necessary to count milligrams of calcium, sodium, et cetera in foods. If you simply maintain a balanced, high-quality diet, you will get enough but not too much of everything. Unless you have special restrictions, include the full range of natural whole foods types in your diet: vegetables (including legumes), fruit, nuts and seeds, healthy oils, whole grains, dairy, fish, and unprocessed meats. Minimize your consumption of refined grains, sweets, processed meats, and fried foods.
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Electrolytes and Exercise
Before the sports drink was invented in the 1960s, the term “electrolytes” was not widely known. Today, virtually every runner is familiar with the term because electrolytes are touted as key functional ingredients in sports drinks and other ergogenic aids. A typical sports drink contains 160-220 mg of sodium, 45-90 mg of potassium, and perhaps also a small amount of magnesium per 12-oz serving.
What is the function of electrolyte minerals in such products? The one proven benefit of consuming fluids containing electrolytes (particularly sodium) during exercise is that it stimulates thirst and thereby increases the amount of fluid consumed and reduces dehydration. A study recently published in the International Journal of Sports Nutrition & Exercise Metabolism reported that sodium ingestion before exercise has the same effect on drinking and dehydration during exercise.
The other purported benefits of consuming electrolyte-containing fluids during exercise are either exaggerated or mythical. For example, it is widely believed that, in the right amounts, electrolytes increase the rate at which fluid is absorbed through the intestine. But research has shown that, at most, electrolytes have only a small effect on how quickly fluids are taken into the blood stream.
Electrolytes are also believed to reduce the risk of hyponatremia, a potentially lethal dilution of the blood sodium level that occurs when prolonged exercise resulting in large quantities of fluid and sodium loss is combined with very large amounts of fluid intake. It makes sense that a sports drink containing sodium would work better than plain water to prevent blood sodium depletion from getting out of hand. But even sports drinks have much slower concentrations of sodium than sweat does, so drinking too much of them is almost as problematic as drinking too much water.
Experts say that by far the most effective way to prevent hyponatremia is to avoid drinking too much of anything. Taking in sodium provides a little extra insurance, but that’s all. The optimal rate of fluid intake during prolonged exercise is that which is dictated by your thirst.
Another widely held belief that turns out to be untrue is that electrolytes can prevent exercise-induced muscle cramping. There is in fact very little evidence that cramps are caused by electrolyte depletion in the body or by dehydration. Cramps almost always occur in the absence of extreme dehydration and electrolyte depletion during unusually prolonged or intense exercise in individuals who are historically susceptible to the problem, suggesting other causes.
However, there is evidence that consuming fluid and salt during prolonged exercise may at least delay cramping in those who are susceptible. In a study from the University of North Carolina, cramp-susceptible athletes were able to exercise twice as long before experiencing cramps when they consumed a sports drink during activity than they when they did not drink.
Finally, studies looking at the effects of electrolytes on endurance performance have generally found no benefit. Most recently, New Zealand researchers compared the effects of salt ingestion or placebo combined with ad libitum water intake on performance in a 72K time trial in a group of nine well-trained cyclists. There was no difference in the time it took them to complete the test.
All in all, the most up-to-date research suggests that consuming electrolytes during exercise through sports drinks and other ergogenic aids can’t hurt, and it might help a little.