Does salt dehydrate you? (The truth about sodium and dehydration)

From the desk of
Robb Wolf
ScienceDoes salt dehydrate you? (The truth about sodium and dehydration)

Does salt dehydrate you? The short answer is no. Dehydration is net water loss from the body, and consuming salt does not cause this condition.

Sure, if you demolish a bag of pretzels, you’ll get thirsty. But this doesn’t mean that salt dehydrates you. Rather, you end up thirsty because your body recognizes that your blood sodium levels are rising. Drinking water balances that out.

Most health-conscious people, however, aren’t getting enough sodium. They’ve made the smart move of ditching processed food—most folks’ main source of sodium—but they have simultaneously shunned the salt shaker due to misinformed guidance around sodium.

Exacerbating this problem is the widespread call to drink more water, no matter what, even if you’re not thirsty. In athletics, this practice has led to serious complications and even fatalities.

Even in everyday life, the quest to prevent dehydration can be harmful. People suffer from brain fog, fatigue, weakness, and muscle cramps. Then, to alleviate these symptoms, they might drink more plain water… which, ironically, worsens the issue.

I’ll cover how to prevent hydration-related problems at the end of the article. First, let’s clear up some confusion about dehydration.

The Truth About Dehydration

The truth about dehydration is that healthy adults rarely become dehydrated. Despite what you may have read, it’s not a big problem.

Yes, certain groups (like the elderly) are more susceptible. But that’s usually due to diuretic drugs, thirst regulation problems, and immobility.

The definition of dehydration is net water loss from the body. “Severe” dehydration starts around 5% of body weight losses, but anything over 1% is typically considered dehydration by the medical literature.

Dehydration is often conflated with hypohydration. Hypohydration is the state of depleted body water, dehydration is the process of getting there. Since they’re used interchangeably, I’ll be doing the same.

The causes of dehydration fall into four main categories: (Note: Salt is NOT on this list).

  1. Water loss through the skin. (Sweat).
  2. Water loss through the gut. (Feces, vomiting, diarrhea).
  3. Water loss through urine. (Diuretics, low-carb diets, fasting).
  4. Not drinking enough water. (Immobility, impaired thirst mechanism, etc.).

Of the four, sweat is the biggest cause of dehydration in athletes. Especially in warm or humid climates.

Organizations like the American College of Sports Medicine (ACSM) urge us to prevent dehydration at all costs. They encourage athletes to replace ALL the water lost, even when they’re not thirsty.

A 2019 systematic review examined this prescription. They reviewed the literature on both hydration strategies—drinking to thirst vs drinking to prevent mass loss—and found no performance differences between the two.

This is significant. Dehydrated cyclists and runners performed just fine!

We’re meant to get a bit dehydrated from exercise. It’s healthy. What isn’t healthy is over-hydrating with plain water.

The Danger of Hydrating Without Salt

You lose both water and sodium through sweat. Both need to be replaced to feel and perform your best.

This seems obvious, but it’s not common knowledge. Most people just replace the water.

Over-watering is rampant in the world of endurance sports. The typical marathon course has watering stations every couple of miles, encouraging runners to drink beyond the dictates of thirst.

Over-watering has visible consequences at the finish line. Athletes stumble around in a state of delirium, often needing immediate medical care.

Why? Hyponatremiathe medical term for low blood sodium levels. All that water has diluted their blood.

Exercise-associated hyponatremia affects around 15% of elite endurance athletes, and many have perished from the condition. Believe it or not, no deaths related to dehydration have been reported in the literature.

Unless you’re an elite athlete, you probably won’t develop hyponatremia this way. But if you’re active, eat a Paleo or keto diet, sweat profusely, or play “hide the salt shaker”, you’re probably not getting enough sodium.

Sodium and Hydration

Sodium doesn’t dehydrate you. It hydrates you.

Consuming sodium replaces what’s lost through sweat, urine, and other bodily fluids. It keeps your bodily fluids properly balanced.

This isn’t how most people think of hydration, but if you look in a medical textbook, you’ll find that hydration status is all about proper fluid balance.

Proper fluid balance means proper blood flow, proper blood pressure, proper thermoregulation (sweat), proper detoxification (sweat, urine, and feces), and much more. After all, we’re mostly water. Getting that water to the right places is essential.

Your body doesn’t leave fluid balance up to chance. The main organs governing fluid balance are the brain and the kidneys, and they’re aided by hormones. This system is constantly scanning and optimizing the levels of sodium, potassium, and water in the blood.

Sodium, for instance, is the primary mineral that regulates blood volume. That’s why humans evolved a taste for salty things. We need it.

And if we don’t get enough sodium, blood volume can fall, causing a variety of symptoms. This is most obvious in POTS (Postural Orthostatic Tachycardia Syndrome), a condition of low blood volume that causes dizziness and rapid heartbeat upon standing. Salt supplementation improves these symptoms by increasing blood volume.

How much we drink also affects fluid balance. That’s where thirst comes in.

Drink To Thirst

“Drink to thirst” is one of my hydration mantras. That’s because thirst is a finely-tuned system. Our bodies generally do a great job of telling us when we need water.

There are a few exceptions where this system becomes a little less reliable, though. High altitudes, conditions like SIADH, and certain medications can throw off the thirst mechanism. But most of the time it’s on point.

How does thirst work? It begins in the brain, where osmoreceptors perpetually scan the sodium concentration (osmolality) of your blood. If the osmolality is too high, it indicates more fluids are needed, and you get thirsty.

Antidiuretic hormone (ADH) also influences hydration. When blood volume is low (indicating low fluids), your brain’s pituitary gland secretes ADH to:

  1. Slow urinary fluid losses
  2. Make you thirsty so you’ll and drink something

Drinking to thirst won’t always prevent dehydration. (We covered this research earlier). But some level of dehydration during sweaty activities is normal. And eventually, thirst will bring you back to homeostasis.

When You Need More Sodium For Hydration

“Stay salty” is another hydration mantra of mine. It’s why LMNT has 1000 mg of sodium per stick.

We’re drinking to thirst AND we’re staying salty because hydration = water + electrolytes. Taking sodium along with water replaces what’s lost through sweat, urine, and other excretions.

At a baseline, most people need more sodium. Based on the literature, the sweet spot looks to be around 4–6 grams of sodium per day (2.5 teaspoons of salt) for heart health.

But 4–6 grams is just a starting point. Many factors increase sodium needs beyond baseline. These fall into three main buckets:

  1. Lifestyle factors
  2. Dietary factors
  3. Other factors

#1: Lifestyle factors

The more you sweat, the more sodium you’ll need. Factors that increase sweat loss include:

  • Exercise volume, intensity, and frequency
  • Temperature and humidity
  • Airflow (breeze)
  • Clothing
  • Genetics

Combine a few of these factors and your sodium losses can be quite sizable. For instance, athletes exercising in warm climates have been shown to lose up to 7 grams of sodium daily.

When I’m rolling in the heat, I’ll often take more than one stick of LMNT to rehydrate. If I don’t replace that salt, my energy for the rest of the day will fall somewhere between mediocre and Paul Blart after a rough day.

#2: Dietary factors

There isn’t much sodium in a whole foods diet. You rely almost solely on the salt shaker, and most of us don’t shake it enough.

And when you combine a whole foods diet with a keto or fasting template, that’s a recipe for sodium deficiency. Why? Because both keto and fasting keep the hormone insulin low, which in turn increases urinary sodium loss.

It’s a quirk of physiology that demands a salty adjustment. An added gram or two of sodium per day does wonders for preventing keto flu. But keep in mind, one can experience these symptoms on any whole-food diet that is lacking adequate sodium.

#3: Other factors

Here are some other situations that affect sodium needs:

  • Pregnancy or nursing
  • Conditions like POTS
  • Heart or kidney issues
  • Illnesses that cause sweating, diarrhea, or vomiting
  • Taking certain medications

Talk to your medical professional about sodium needs and fluid needs when it comes to these sorts of medications and conditions.

A Final Hydration Mantra

I’m glad we could clear up the confusion on sodium today. I’ll leave you with my final hydration mantra. It covers what you need to know in a single sentence:

Drink electrolyte water to thirst.

If you drink electrolyte water to thirst, you’ll replace what’s lost through sweat and maintain proper fluid balance. Sodium is probably the most crucial electrolyte for hydration, but potassium and magnesium have their benefits too.

LMNT is convenient in that it has 1000 mg sodium, 200 mg potassium, and 60 mg magnesium in each grab-and-go stick pack. But I like to remind folks that my coaches and I made electrolyte homebrews for years before we co-founded LMNT. And in that time, we came up with some pretty tasty homemade electrolyte drink recipes.

Try them out and let me know what you think!

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