If there’s one piece of advice you’ve probably heard over and over again for fasting it’s this: take magnesium. But if you’re like most people, you probably have no idea what the magnesium’s doing in your body or why it’s important.
Magnesium is one of several essential minerals called electrolytes, which again… we all know to be important, but we don’t all know why they’re important.
You may know that electrolytes have something to do with the way water behaves in your body, but what exactly is an electrolyte? Simply put, it’s a mineral that, when dissolved in a solution, is electrically charged—electrolytes are “electric.” They’re critical for a bunch of essential functions. Yes, they help maintain fluid balance, but they also aid in muscle contractions, keep your heart beating normally, and help your body send signals from your nervous system to cells throughout your body.
Since you aren’t eating during a fast, you aren’t getting electrolytes through food. Even if you’re time-restricted-feeding (doing a 16:8 for example), there are 16 hours of the day when you aren’t getting a consistent stream of electrolytes into your body. Even non-fasters are at risk for electrolyte deficiency. Supplementation may be critical to help keep your body functioning properly, especially on a longer fast.
Supplementing with two key electrolytes—magnesium and sodium—may also help you avoid some of the nasty side-effects of electrolyte depletion.
For this article, we’ll focus on magnesium.
Magnesium is an essential mineral, meaning that we cannot make it in our bodies; we have to get it from food and beverages or supplements. Our bodies use magnesium to aid enzymatic reactions, energy production, membrane function, regulation of calcium and potassium, plus cardiac and brain function, just to name a few.
Magnesium also plays a role in transporting calcium and potassium ions across cell membranes. Without those two minerals, your muscles may have difficulty contracting properly, which is why a common symptom of low magnesium levels is muscle cramping—something you might experience when fasting.
Other symptoms of low magnesium
How can you tell if you might have a magnesium deficiency? Your body’s pretty good at telling you when the magnesium tanks are nearing the danger zone. Aside from the muscle cramping mentioned above, other symptoms of low magnesium include fatigue, weakness, irritability, and vertigo.
Recommended supplementation dose
Most people are at risk for sub clinical deficiency in magnesium, even when they’re not fasting, so you likely need more than the suggested RDA (300-420mg a day). A few studies have shown that even when consuming close to the recommended amount, participants were still in a negative magnesium balance, potentially setting them up for higher risk of chronic disease and other long term health issues.
In addition, during a fast, your body actually starts getting rid of magnesium in order to preserve other electrolytes (it has to do with the electric charges of the molecules).
During a prolonged fast, your kidneys can excrete magnesium at a shockingly high rate. In one study, the kidneys of participants on a mutli-week fast (seriously, mutli-WEEK), were excreting magnesium at a rate 4-5 times higher, than normal. It seems the deeper into your fast you go, the more magnesium you’re prone to lose. Across a few different studies of prolonged fasting in obese males, the average magnesium loss per day ranged from 83 mg to 203 mg.
So, while fasting, it’s reasonable to say that a range from about 400-600 mg per day would be appropriate to provide the body with the essential magnesium it needs to function optimally and to prevent the nasty symptoms of magnesium deficiency.
Types of magnesium
The type of magnesium you choose will impact how, when, and where your body absorbs it. This is important for maintaining a steady drip of magnesium throughout the day and avoiding any gastrointestinal issues.
1. Magnesium oxide is one of the most common forms of magnesium. In all likelihood, if you purchased a magnesium supplement in the past, this is the one sitting on your shelf. The downside of magnesium oxide is that if taken in large quantities (the quantities you’d need on a fast), it can have laxative effects. Not all magnesium oxide is absorbed, so once it reaches the small intestine, it draws in additional fluid and stimulates bowel movements. The other problem with magnesium oxide is that your body absorbs what it can, and excretes the rest pretty quickly, so if you just take it once or twice a day, you won’t maintain a steady level of magnesium in your bloodstream.
2. Magnesium L-threonate is a novel and proprietary form of magnesium developed by scientists at MIT. It’s better absorbed than magnesium oxide and has been used to support brain health and sleep. In this form, magnesium is bound to L-threonate, a magnesium transporter that helps it cross the blood/brain barrier. Magnesium L-threonate has been shown to have a calming effect, which is why people often take it in the evening.
3. Magnesium glycinate is another highly bioavailable form of magnesium and has been used in the optimization of sleep, memory, bone health, blood pressure and blood sugar control, headaches and leg cramps.
4. Magnesium malate is considered a magnesium salt with high bioavailability that helps support cellular energy production.
5. Slow release magnesium is also becoming increasingly popular. It tends to be more expensive since it relies on cutting-edge technology to encapsulate the magnesium – usually in a lipid or fiber outer later – so your body has to break down the capsule before it can absorb the magnesium itself.
In an ideal scenario, you’d supplement with multiple types of magnesium whenever you’re not eating — whether it’s a shorter TRF window like a 16:8, or a multi-day fast — and your magnesium intake should include at least one or two slow-release forms to optimize a steady uptake throughout the day.
Read PART TWO for the second of the BIG 2 electrolytes you’ll need to make your fast a little happier: sodium.