Electrolytes and fasting: benefits and best sources

Intermittent fasting is a big deal these days, I wrote my first article on IF back in 2005. Although we’ve learned an enormous amount in that time, there is still far more that we do not know than we do. The main benefits ascribed to fasting (intermittent or more prolonged) generally focus on weight loss, a shift towards a more fat-centric metabolism (including a ketogenic state), the potential of enhanced longevity, and the much talked about topic of autophagy where damaged cells and tissues may be removed and effectively recycled. One thing that seems fairly certain: We tend to eat too much and too often, at least in our cushy, Westernized lives. From my perspective, it is unclear if there is a significant benefit to fasting above and beyond “simply” eating a species-appropriate diet. I was arguably one of the first popular authors on the scene talking about fasting, and although I think it’s a great tool, it is not the only tool, it needs to be done correctly (with a specific goal in mind) and it must be understood that fasting is not the beez kneez for everyone.

Currently, the optimal fasting protocol remains unknown, and I’ll wager that “optimal” fasting will depend entirely on both the individual and the goals of that individual. In other words, I suspect there will not be a one-size-fits-all approach. Some of the questions hanging out there about fasting include: How long should it be? Does the intake of any calories, or even noncaloric substances like coffee or electrolytes alter the benefits of fasting? If one uses an intermittent eating schedule, should the bulk of calories be consumed early, or late? That’s a shortlist of the questions that need to be looked at in a more rigorous scientific way but for the sake of this article, let’s assume that fasting IS generally beneficial, particularly if one is more comfortable while in the fasting state. With that perspective in place, one of the most important features of the fasting process will end up being proper electrolyte supplementation.

This may seem an odd angle to take when considering fasting, but when we understand the metabolic process called “the natriuresis of fasting” (significant loss of both water and sodium due to the low insulin state of fasting) this may make a bit more sense. Similar to ketogenic diets, when fasting is implemented for medical purposes, significant attention is given to providing adequate electrolytes, particularly sodium, to make the process both safe and effective. 

Take a moment and re-read that last section. I don’t want to do a big appeal to authority, but if the medical establishment recognizes that fasting/ketosis requires significant electrolyte/sodium supplementation, it might behoove us to give that idea some airplay and experimentation.

My inbox is literally overflowing with questions on this topic. Folks want to know which electrolytes to take, in what forms, which brands, how much, how often, and what benefits they can expect. Perhaps one of the most common questions I’ve even been asked is if electrolytes will break a fast. Let me answer the last question first. No, electrolytes shouldn’t interfere with a fast. They don’t have calories, so they don’t stimulate pro-growth pathways like mTOR (which is activated by carbs/insulin, and branched-chain amino acids). With mTOR suppressed, a pathway called AMPK stays active. AMPK drives many fasting-related benefits: fat-burning, autophagy, and more. Some folks are even concerned about things like stevia causing an “insulin response” which might boot one out of the beneficial window that fasting provides. Although we have no research on this topic, I find this to be a BIG reach. IF one were to release any appreciable insulin while fasting, blood glucose will decrease and one could argue that perhaps 20 min later, one might be in an even deeper state of ketosis. Again, this is all fairly speculative, but I’ll make the case in a moment that proper electrolyte supplementation can make or break a fast... it’s more important to navigate the time IN fasting than the minutia of if stevia may kick one out of ketosis. All that said, if one is concerned about the potential problems of stevia, using something like the LMNT Raw Unflavored solves that issue.

Far from interfering, electrolytes can enhance your fast, at least in the sense of reducing side effects. If you’re cramping up, feeling sluggish, or performing poorly while fasting, there’s a good chance you’re low on sodium, and if you are experiencing all those symptoms, it’s more likely that you will bail on your fast. 

As I alluded above, folks (especially low-carb and active folks) need more sodium, and I haven’t been shy to say it. Well, guess what? You really need more sodium during a fast.

Today I’ll cover this topic from a theoretical and practical perspective. You’ll learn why you should take electrolytes during a fast, which ones to take, and recommended amounts. Keep reading.

Electrolytes Primer

Throughout your body, a handful of electrically-charged minerals help your heart beat, your muscles contract, and your brain cells communicate. These minerals are called electrolytes.

The main electrolytes are sodium, potassium, magnesium, calcium, phosphate, chloride, and bicarbonate. They’re all important, but after carefully reviewing food logs, I’ve found that people are most likely to be deficient in these three:

  • Sodium maintains fluid balance (blood flow) and helps nerve impulses fire. Along with chloride, it’s found in salt (NaCl).  
  • Potassium works together with sodium to regulate blood pressure and fluid balance. It’s found in fruits and vegetables. 
  • Magnesium supports muscle function, mood, and bone health. It’s found in leafy greens. 

If your electrolyte levels become unbalanced, you may experience muscle cramps, low energy, headaches, irritability, and neurological symptoms. These side effects can easily occur during a fast.

Why Fasting Depletes Electrolytes

Many things can deplete your electrolyte levels: sweating, overwatering, vomiting, diarrhea, low-carb diets, and—yes—fasting. Losing electrolytes through sweat or feces is easy to grok (out they go!), but losing them through a low-carb or fasting regimen isn’t so straight forward.

Strap in for the next few paragraphs. We need to geek out on some science. 

The first thing to understand is that fasting and the ketogenic diet provoke similar metabolic responses. (Keto is, in fact, a “fasting-mimicking diet”). Both regimens, because they minimize carbs, also minimize spikes in blood sugar. And when blood sugar is minimized, insulin is minimized too.

Insulin is best known as an energy storage hormone—a chemical messenger that commands blood sugar out of your blood and into your cells. But bossing around blood sugar isn’t enough for insulin. It also needs to boss around your kidneys. 

Hold onto that sodium, says insulin to your kidneys. Don’t pee it out.

And your kidneys listen. This is why folks with perpetually high insulin levels (like type 2 diabetics) tend to be salt sensitive. Since they can’t pee out sodium, they can’t effectively regulate blood pressure.

The opposite is true when insulin levels are low. You pee out more sodium. And no dietary strategy (not even keto) lowers insulin more than fasting. 

In some people, insulin levels are immeasurable during a fast. Great for burning fat, but awful for retaining sodium. Let’s look at some published examples now. 

Research On Electrolytes While Fasting

In the limited research that exists, we find that sodium, potassium, and body water are energetically peed out during extended fasts. As far as electrolytes go, you see significant sodium excretion (called natriuresis) that peaks around day four of the fast, with a similar but less pronounced pattern of excretion for potassium.

In one 1970s experiment, a morbidly obese man was fasted for 382 days—an intervention that more than halved his body weight. According to the authors, there were no complications worth mentioning.

It’s interesting to note, however, that his sodium and potassium levels dropped significantly during the first 100 days of the fast. They later stabilized, but one wonders if these stabilizing electrolytes were leached from his bones. When you’re low on electrolytes, your body goes digging for them.

Another study took a different approach, giving 46 obese individuals a daily electrolyte supplement over the course of a six week fast. The group lost on average 56 pounds “without producing severe electrolyte disturbances seen with other modalities.” In other words, their electrolyte levels remained largely normal. 

Benefits of Electrolytes While Fasting 

Any fast over 12 hours increases the likelihood of electrolyte deficiency. There are two main reasons for this:

  1. Food (especially plant matter) is the main source of every electrolyte except sodium. When you fast, you cut off your supply.
  2. Fasting precipitously lowers insulin levels. As a result, your kidneys start expelling sodium, potassium, and water with great gusto.

Taking electrolytes during a fast can prevent deficiency. This has the following benefits.   

#1: More energy, less keto flu

You’ve probably heard of the keto flu. It’s a term for the low energy, headaches, fatigue, and malaise often experienced during the transition to a low-carb diet. 

Keto flu, though, is often just a case of low sodium. The remedy isn’t to “wait it out”. The remedy is to increase salt intake.

The same holds true for fasting. Like keto, fasting lowers insulin and causes considerable sodium loss. That sodium needs to be replaced. Specific recommendations are coming in the next section.  

#2: Less weight rebound

If you step on the scale a few days into a fast, you’ll likely see a lower number than expected. Sorry folks, this isn’t fat loss. It’s water loss.   

Right. When you fast, your body breaks apart glycogen (stored sugar) to meet your brain’s ravenous glucose needs. This process, called glycogenolysis, releases torrents of water which you subsequently pee out. Water is heavy, and your body weight decreases accordingly.

When you start eating again, glycogen reforms and the weight comes roaring back. Sodium supplementation dampens this effect, reducing the post-fasting weight gain to only 39% of the original amount lost.

#3: Exercise performance 

During exercise, you lose sodium through sweat. Combine this with fasting-induced sodium loss and you have a strong case for supplementation. 

For me, this one hits close to home. Just a couple years ago, I supercharged my Jiu-Jitsu performance by taking more electrolytes (especially sodium) in close proximity to training. Before fixing my sodium, I was struggling out there. I feared it was age-related. I’m glad I was wrong.

Another quick example. A good friend of mine recently took silver at the Pan Ams—the largest Brazilian Jiu-Jitsu tournament in North America. He reported that increasing his electrolyte intake gave him a gas tank like he’d never seen before.

Super anecdotal, I know, but worth chewing on. That said, let’s shift to a more scientific note.

#4: Prevent hyponatremia

Low sodium, or hyponatremia, is a dangerous and sometimes fatal condition that afflicts—according to one source—around 15% of endurance athletes. The root cause is bad hydration advice. Heeding the battle cry of “drink more water”, athletes pound fluids beyond the dictates of thirst and end up diluting blood sodium levels.

Hyponatremia can be reversed, it’s been shown, by drinking a saline (salt water) solution. And so if you’re only drinking water—but not consuming electrolytes—during a fast, you may end up with low sodium symptoms. 

How To Take Electrolytes While Fasting 

Next I’d like to offer practical advice on electrolyte supplementation. I designed my protocol to provide a bit more sodium, potassium, and magnesium than the average person needs. It may not hit your needs exactly, but it should get close. 

I generally suggest people take 5,000 mg of sodium, 1,000 mg potassium (potassium chloride or citrate), and 300 mg magnesium malate each day in addition to food. I believe these are reasonable dosages for fasting days too.

You might be thinking that five grams of sodium sounds high. Isn’t salt bad for your heart? Not according to a 2011 paper published in the Journal of the American Medical Association (JAMA). In this large cohort study, folks excreting (consuming) 5 grams sodium per day had fewer heart attacks and strokes than those consuming the government-recommended limit of 2.3 grams. Five grams sodium was the sweet spot. 

Moving on, a gram of daily potassium is only about ⅕ of the RDI, but should stabilize potassium levels during a fast. Just be sure to eat a potassium-rich diet during feeding periods.

Finally, 300 mg magnesium will meet basic requirements and can also help you relax during a fast. This comes in handy when you go to bed hungry, which is never easy.

To hit your electrolyte targets, you have a couple options: buy supplements separately or take a preformulated mix. For reasons of convenience, I prefer option B. That’s why I created LMNT Recharge, my no-nonsense electrolyte blend.

Whichever route you go, I hope you’ll incorporate electrolytes into your fasting regimen. Electrolytes can prevent discomfort and even boost your energy. We like it when that happens.