Ascent Insights

Choosing Magnesium Supplements

Posted by Ascent Labs on

Choosing Magnesium Supplements

Maybe you’re thinking about taking magnesium supplements because you’ve heard that it’s good for blood pressure, heart health, sleep, mood regulation, energy, or for all of the reasons above. 

So which one should you take? From magnesium oxide to magnesium sulfate to magnesium glycinate to magnesium citrate– yes, there’re even more types– what’s the best magnesium supplement to take?

There’s some caveats that affect how well your body absorbs different forms of magnesium, so it’s important to figure out the best form that works for you. The key to choosing magnesium is understanding bioavailability, which we’ve broken down in this blog for you

But for the specifics on taking the best magnesium supplement, read on.


What is magnesium?
Magnesium is a dietary mineral that promotes essential functions in your body. It’s a cofactor for more than 300 enzyme systems that regulate your body, and it’s required for energy production, carbohydrate metabolism, and DNA and protein synthesis. Magnesium also contributes to the structural development of bone, supporting bone density and helping to prevent onset of osteoporosis

People also take magnesium for sleep. Magnesium supplements for sleep were found to help improve insomnia symptoms in one study, and another found that taking magnesium and melatonin in a vitamin B complex had a beneficial effect on treating insomnia. 

Taking magnesium for sleep is sometimes compared to taking melatonin as a sleep aid. Melatonin is the body’s natural sleep hormone, which signals to your body when it’s time to fall asleep. 

While differences between the two haven’t been fully explored, other studies have supported the beneficial effects of magnesium and melatonin taken together for sleep. Whether you take a melatonin or magnesium supplement for sleep, both have been found to improve sleep disorders across various studies. 

Magnesium for mood regulation and decreasing PMS symptoms is yet another reason people supplement this mineral. One study recommended taking magnesium to help reduce symptoms of depressive disorders that onset from mineral deficiencies.

From all the different applications, magnesium is found to be an essential mineral that affects many aspects of human health and our body’s ability to function well. 


Recommended Dietary Allowance (RDA) for magnesium.

The standard guidelines for supplements are defined quite broadly. Currently, it’s recommended to get about 400mg of magnesium per day for men, or 300mg per day for women. This is what is recommended as a sufficient dosage to avoid a magnesium deficiency. 

However, individual needs vary more broadly based on weight. For example, a person who weighs about 135 pounds would need around 400 mg, while someone who weighs 165 would need closer to at least 500 mg.

You can also use this handy calculator to estimate the best magnesium dosage for you.


Building up to it

Because of the laxative side effects of taking too much magnesium, it’s important to slowly build up to taking the dosage of magnesium you ideally need.

Magnesium draws water into the intestines and relaxes the bowels, so taking it can have an osmotic laxative effect.In one study, magnesium was used to help people with chronic constipation, with successful results.

Side effects of taking too much magnesium at once include:

  • Diarrhea 
  • Nausea
  • Cramping 
  • Vomiting 
  • Increased urination

To avoid side effects, it’s recommended to slowly increase the amount of magnesium you take per day spread out throughout the course of your day.

Start with taking 100 mg a day, at two doses of 50 mg during the day, for about a week. If your body tolerates this, increase to 200 mg a day, at two doses of 100 mg, for another week. Continue increasing in 100 mg increments until you reach the magnesium dosage you desire without any side effects. 

So let’s go over the ways to get a sufficient daily intake of magnesium.


First things first: in your diet. It’s not enough.

Magnesium is in many whole foods such as leafy vegetables like spinach or chard, as well as in legumes, nuts like almonds, seeds, and whole grains. Many kinds of processed foods are fortified with magnesium, such as breakfast cereal. 



But while these foods might be rich in magnesium, it doesn’t guarantee that your body is absorbing it optimally. 

These same foods are high in oxalates and phytic acids, which are produced as end products of metabolism. Oxalates occur when oxalic acid binds to minerals, hindering their absorption. Oxalates and phytic acids in these foods can prevent absorption and actively reduce bioavailability by as much as 60%

So even if you’re eating a whole foods diet with many foods rich in magnesium, they’re consumed with other compounds that inhibit optimal absorption. The best way to make sure that you're getting enough magnesium in your diet is to also take dietary supplements.

When choosing magnesium supplements, finding the cheapest option doesn’t work out. Here's a small breakdown of some options we've ranked on personal choice. 


The worst: magnesium oxide.

The most common form of magnesium you're going to find on the shelf is magnesium oxide. This is our worst option and our last choice when it comes to choosing magnesium supplements. 

Magnesium oxide has a bioavailability of around 4%, which is abysmal. It’s cheap, which is its greatest draw. But for the amount that you’re not absorbing, you might as well choose something else.  

Our score: Solid D/C- / $

Similar tiers to magnesium oxide include magnesium chloride, which also has low bioavailability. 


Uncomfortable side effects: magnesium salts (magnesium sulfate)

Magnesium salts are about as ineffective (for the purpose of supplementing magnesium efficiently) as magnesium oxide. 

This type of magnesium supplement does have a higher bioavailability value than magnesium oxide. The problem is that these are also osmotic laxatives, in that they draw out water from your intestines and relax your bowels. Taking a sufficient amount of magnesium sulfate can easily be overdone, resulting in a strong laxative side effect. In one study, all subjects experienced mild to moderate diarrhea after taking a high dosage of magnesium sulfate.

Magnesium salts like magnesium sulfate are typically used to relieve constipation, for which they work very well. But for supplementing magnesium, it’s not a comfortable choice for most people.

Our score: Solid C / $


Better: magnesium amino acid chelations (magnesium glycinate, magnesium l-aspartate, etc)

A tier above magnesium oxide are magnesium amino acid chelations. These include magnesium glycinate (technically named di-glycinate) and magnesium l-aspartate. These supplements can be more expensive, but they have a more moderate bioavailability value than magnesium oxide, and without the more intense laxative effect of magnesium salts. 

Magnesium amino acid chelations actually absorb through unique mechanisms. Because they are absorbed in a different part of the small intestine, they might be easier for people with gut conditions to supplement magnesium. Although they can be pricier, these might be worth a look. 

Our score: Good B+ / $$-$$$

Magnesium glycinate binds magnesium to glycine, an amino acid that is also known to help promote sleep. People take magnesium glycinate for sleep, and find it to have beneficial results. 


Our best pick: Magnesium citrate.

Our personal choice would be magnesium citrate. 

Magnesium citrate is a form that binds to citric acid. It has a higher rate of potency compared to magnesium oxide and other forms of magnesium in various studies. It has anywhere between 3 to 10 times the bioavailability of the oxide form

Magnesium citrate also tends to run cheaper than some of your other options, making it the best balance between budget and boost. 

Our score: Best A+ / $-$$