Does salt help with hydration? The science-backed answer

From the desk of
Robb Wolf
ScienceDoes salt help with hydration? The science-backed answer

Most people don’t think of salt when they think of hydration. They think of salt as a condiment to accompany steak, eggs, and possibly tequila shots.

They do think of water though. Lots of water. From a young age, we’re told to drink eight glasses per day. It’s supposed to be healthy.

But there never was any science behind eight glasses per day. The recommendation emerged in 1945 from the bowels of American government, and has since clung to the public consciousness like a hungry squirrel to the last acorn on Earth.

Meanwhile, salt has been wrongfully demonized as the cause of heart disease, high blood pressure, and other maladies. As a result, we’ve created a situation in which people are:

  1. Diligently guzzling water
  2. Diligently avoiding salt

Unfortunately, the more salt-free water you drink, the more your sodium needs go up. And since many people shun salt for “health reasons”, these needs are often not being met.

Salt insufficiency has consequences. It’s the scourge of keto dieters and athletes alike. It causes low energy, weakness, muscle cramps, and headaches. In more than a few cases, low sodium has proven fatal.

But getting enough sodium isn’t astrophysics. With a bit of practical knowledge, it’s easy. I wrote this article to share this knowledge and present an evidence-based case for a salt-inclusive hydration strategy.

What Is Salt?

Salt, or NaCl, is a naturally occurring compound composed of the minerals sodium (Na) and chloride (Cl). Sodium and chloride almost always appear together in nature.

Both sodium and chloride are electrolytes—charged minerals that conduct electricity to power your nervous system. Electrolytes also regulate fluid balance, or the amount of fluids inside and outside your cells. Since humans are about 60% water, maintaining this balance is important.

Sodium comes in through diet and goes out through sweat and urine. Whole foods contain a small amount of salt, but most incoming sodium arrives from the salt shaker or as added salt from packaged foods. Salt intakes vary widely by diet.

Salt excretion also varies widely. At equivalent sodium intakes, a sweaty athlete who eats a low-carb (and diuretic) diet, will lose more sodium than a sedentary person on a high-carb diet. So, the sweaty low-carb person will need to consume more sodium to maintain optimal health.

How Salt Helps With Hydration

Hydration has a few definitions, and some are more useful than others. The less useful definitions speak only of water. The better definitions—the ones you’ll find in physiology textbooks—refer to proper fluid balance.

Proper fluid balance means maintaining the Goldi-locks amount of fluids to keep your blood flowing through your veins, your digestive system running smoothly, and your brain floating in your skull.

Water intake is one essential input to the fluid balancing equation. We need water to live. But water intake is just one of four factors affecting your hydration status.

4 Hydration Factors

  1. How much water you’re drinking
  2. How many electrolytes you’re consuming
  3. How much water you’re losing
  4. How many electrolytes you’re losing

As you can see, water is only half of the picture. The other half is composed of electrolyte considerations.

Of the electrolytes, the most important for fluid balance are sodium and potassium. They’re a power couple, like Beyonce and Jay-Z. (Confession: I Googled “power couples” in order to appear in touch with popular culture when making this analogy).

Inadequate intakes of either sodium and potassium has consequences. For instance, diets low in potassium are uncontroversially linked to higher blood pressure. Even the USDA is on board with getting enough potassium.

But sodium is a different story.

Isn’t Salt Bad For You?

Salt has been the villain since 1980. That was the year the US government started chastising citizens to avoid sodium in the name of heart health.

This position was based on research by Lewis Dahl in the 60s and 70s. Dahl found that rats with certain genes would develop high blood pressure (hypertension)—a major heart disease risk factor—at high salt intakes.

Dahl also found links between dietary salt and hypertension in humans, but the data weren’t consistent. Many people who ate loads of salt didn’t have high blood pressure.

In 1988, researchers revisited this question with the landmark Intersalt Study. They sampled over ten thousand people from fifty two regions of the world. In aggregate, did they find a correlation between sodium intake and hypertension? Nope.

But apparently, that didn’t matter. Today, the government continues to rage against salt, and current guidelines call for capping sodium at 2.3 grams per day.

This is irresponsible advice, and not just because I say so. In one watershed JAMA study, restricting salt per government guidelines led to worse outcomes (more heart attacks and strokes) in heart disease patients. The patients with the best outcomes consumed closer to 4–6 grams sodium per day—more than double the recommended amount!

Sodium also gets blasted for its relationship to refined foods. These high-sugar, high-vegetable oil franken-foods are staples of the American diet, and they also happen to be high in sodium. Guilty by association.

Another association: people who consume more soft drinks tend to consume more sodium. Is sodium driving obesity and high blood pressure? Or is it high fructose corn syrup? My money’s on the sugar.

Let’s get back to hydration though. We’ve seen why salt has been vilified. Now we need to see why avoiding salt is opposed to healthy hydration.

The Problem With Drinking Too Much Water

Your body is an impressive fluid balancing machine. If you mess up your water or electrolyte inputs, your body handles the situation.

For instance, if you drink too much water, your brain stops secreting antidiuretic hormone (ADH) and you pee out the excess. And if you take in too much sodium, the excess sodium goes out through urine. It’s a well-oiled machine.

Problems arise, however, when you introduce variables like sweat, exercise, and excess fluid consumption. Your body can’t keep up, and fluid balance goes haywire.

This is what happens to elite endurance athletes. They lose sodium and water through sweat, but they only replace the water. And they replace it with vigor.

But exercise impairs the fluid balancing system. When we exercise for long periods, we have trouble suppressing ADH. As a result the fluid balance becomes too watery and blood sodium levels plummet.

The medical term for low serum sodium is hyponatremia. The symptoms of hyponatremia include muscle cramps, headache, weakness, fatigue, and confusion. In severe cases, hyponatremia can cause seizures, brain damage, and death.

Conservatively, exercise-associated hyponatremia affects about 15% of endurance athletes. Why is it so common? Because organizations like the American College of Sports Medicine (ACSM) have scared the public into over-hydrating. Per ACSM guidelines, athletes are supposed to drink enough water to cap body water losses at 2% of body mass.

But dehydration (net water loss) and hypohydration (low body water) aren’t the evils they’re made out to be, at least not compared to hyponatremia. For one, losing body water during exercise doesn’t appear to affect athletic performance. And more importantly, sports-related dehydration isn’t killing anybody. Hyponatremia is.

Serious cases aside, even mild sodium deficiency can impair one’s quality of life. And certain groups need to work extra hard to get enough salt.

Who Needs Extra Salt To Stay Hydrated

Most people would do well to consume around 2–3 teaspoons of salt (4–6 grams of sodium) per day. The following groups may need even more.

#1: Low-carb dieters

On a low-carb or ketogenic diet, two factors increase the risk of sodium deficiency:

  1. Whole food keto diets are naturally low in sodium
  2. Low-carb diets are natriuretic (you lose more sodium through urine)

I believe inadequate sodium is a primary cause of the headaches, low energy, and cramps collectively known as “keto flu”. I’ve seen it so many times. Fix the low sodium and you fix the symptoms.

#2: Athletes

Athletes have increased hydration needs. They lose more fluids through sweat and respiration, and these fluids need to be replaced.

But they don’t need to be replaced immediately. If sodium-free fluid replacement is too aggressive, they’ll develop exercise-associated hyponatremia.

Increasing sodium intake can prevent (or reverse) this complication. In one 2014 randomized controlled trial, distance athletes reversed dangerously low sodium levels by simply drinking salt water.

#3: Those living in extreme climates

Obviously, warm climates increase hydration needs. Active people exercising in the heat can lose up to 7 grams of sodium per day.

But did you know cold and altitude also impact hydration status? Cold and altitude:

  • Have a diuretic effect
  • Increase metabolic fluid losses
  • Artificially suppress thirst
  • Cause increased sweating in your warm gear

So, if you’re hitting the slopes, be sure to bring electrolyte water.

Hydrating With Salt and Water

Most of what you need to know about hydration can be reduced to a single sentence:

Drink electrolyte water to thirst.

And if electrolyte water doesn’t sound appetizing, you probably haven’t tried LMNT.

Drink salty water to thirst. That’s it. That’s how you replace the optimal amount of fluids, prevent exercise-associated hyponatremia, and feel and perform your best.

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