Contrary to Popular Opinion, Sodium Is Essential for Hydration

How Much Sodium and Potassium Should You Consume Each Day?

By Roberta H. Anding, MS, Baylor College of Medicine and Texas Children’s Hospital
Edited by Kate Findley and proofread by Angela Shoemaker, The Great Courses Daily

Sodium and potassium work in conjunction with one another and they are essential to our health. Professor Anding explains the amount we should get each day and why you need to adjust your sodium intake if you sweat a lot.

Close up of woman salting a salad
The dietary intake of these two electrolytes is important because sodium is essential for hydration in order to pump water into your cells and potassium helps to pump waste products out of your cells. Photo By goodbishop / Shutterstock

Roles of Sodium and Potassium

Sodium and potassium play many important roles. First, they are necessary for the regulation of blood and other body fluids. They help nerves talk to one another and stimulate the action of muscular activity, proper gland function, and heart activity. 

Sodium is important for maintaining the “electrochemical gradients” and the “membrane permeability” in the cells of the body. This means that sodium is essential for hydration because it pumps water into your cells. 

Potassium functions in the pumping of byproducts or waste products out of the cell and are eliminated from the body. Thus, potassium and sodium serve as the body’s fluid regulator and waste product regulator—two vital roles.

Dietary Sources

We require 500 milligrams (mg) of sodium per day, while the recommended daily maximum is less than 2,300 mg—the amount contained in a teaspoon of salt. You may be unaware of just how many foods contain ample amounts of sodium, though.

A dill pickle contains about 1,700 mg of sodium, and a cup of canned chicken soup has 850 mg. An ounce of pretzels has 486 mg, which would essentially get you close to your biological requirement. 

That’s why it’s not practical to just shoot for that number. Even an ounce of bread—of all types—ranges between 95 and 210 mg of sodium. 

Keep in mind that sodium does not just come from sodium chloride, or table salt. It also comes from sodium propionate, which is added as a preservative, and sodium bicarbonate, a leavening agent.

For potassium, a medium sweet potato that you would bake has 694 mg of potassium. Eight ounces of plain, nonfat yogurt contains 579 mg. 

Three ounces of yellowfin tuna is 484 mg of potassium. A non-cured pork chop has 382 mg of potassium, and a fourth of a medium cantaloupe has 368 mg. 

What are the daily intake requirements for potassium? For adults and adolescents, it’s about 4,700 mg per day; so, the requirement for potassium is relatively large in comparison to sodium. This is why most Americans do not get enough potassium in their diet but consume an excess of sodium.

Children one to three years of age require about 3,000 mg of potassium, children four to eight require 3,800 mg, and children nine to 13 require 4,500 mg. The reason these requirements increase with age is because body weight increases with age. Potassium is stored inside the muscle and the more muscle mass there is, the more potassium that’s needed to be stored.

Considerations for Sodium

When it comes to sodium intake, the recommended daily maximum of 2,300 mg does not apply to all segments of the population. African Americans, individuals who are middle-aged or older, and individuals with high blood pressure should aim to consume no more than 1,500 mg of sodium per day.

One of the challenges with sodium regulation as we age is that often we lose the ability to taste food. Sodium, particularly in the form of table salt, gives food extra flavor. Reducing sodium alone, for an elderly person, often makes them not in favor of eating the low-sodium food.

The absolute minimum requirement for sodium intake is different for younger age groups. For infants 0 to 5 months, it is 120 mg. At one year of age, it is 225 mg. 

For two- to five-year-olds, it is 300 mg. As you approach adulthood, we’re looking at 500 mg. 

Keep in mind, though, that sodium is often lost throughout the day, particularly in sweat during exercise. For example, endurance athletes who exercise for greater than two hours are going to lose significant amounts of sodium due to the loss of excess sweat. The amount of sodium lost in sweat varies significantly among athletes and depends on whether they are salty sweaters.

How do you know if you’re a salty sweater? If you’re done running and you can wipe the sweat off of your face and feel the grains of salt on your face, you are a salty sweater. 

If you live in a humid climate where sweat doesn’t evaporate off your skin, you never get to wipe anything off, other than water. In this case, another way you can assess if you are a salty sweater is if the sweat gets into your eyes; if. it is caustic or painful, you may be a salty sweater. 

The ultimate test, though, is if you hang up your gym clothes and you see the white salt stains under your armpits, then you are a salty sweater. That means you’re losing more sodium than normal in your sweat. 

Stay tuned for tomorrow’s article, where we’ll discuss sodium deficiency in more detail. 

This article was edited by Kate Findley, Writer for The Great Courses Daily, and proofread by Angela Shoemaker, Proofreader and Copy Editor for The Great Courses Daily.

Professor Roberta H. Anding is a registered dietitian and Director of Sports Nutrition and a clinical dietitian at Baylor College of Medicine and Texas Children’s Hospital. She also teaches and lectures in the Baylor College of Medicine’s Department of Pediatrics, Section of Adolescent Medicine and Sports Medicine, and in the Department of Kinesiology at Rice University.

About Kate Findley 408 Articles
Kate is a writer, novelist, and blogger living in Los Angeles. She has been writing for The Great Courses since 2017. It incorporates her two favorite things: writing and learning.