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Magnesium Supplements: Benefits, Side Effects, and Dosage

Written by Lauren Panoff, MPH, RD

Published on September 13, 2021

While some people may get enough magnesium through their diet, many benefit from adding a supplement. If you are not sure how to choose the best one, here are a few things to look for.

Magnesium Supplements: Benefits, Side Effects, and Dosage
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Magnesium is an important micronutrient involved in countless functions in your body. It is found in every cell and serves multiple purposes for overall health.

While magnesium is found widely in the diet, some people are deficient in this nutrient or may choose to take a supplement for additional health benefits.

Choosing the best supplement for you depends on form, purpose, dose, and potential interactions. Here’s our guide for what to look for in a magnesium supplement.

What Is Magnesium?

Magnesium is an essential mineral, meaning that your body can’t produce it, and you have to get it from your diet.

Getting enough magnesium is important because it’s responsible for hundreds of cellular processes in your body.

Without it, these processes don’t work as well, and your health can ultimately suffer.

Magnesium is the fourth most abundant mineral in your body and acts as a coenzyme in over 300 reactions, including energy production at the cellular level.

Most healthy adults have around 25 grams of magnesium in their bodies at any given time. Approximately 50–60% of it can be found in the bones, with most remaining amounts in tissues.

Only 1% circulates in the bloodstream, which remains tightly regulated with any excess being excreted by the kidneys.

Normal circulating blood levels of magnesium for most people are between 0.75 and 0.95 mmol/L.

As for how much magnesium you need, the recommended dietary allowances (RDA) for magnesium fall between 300–400 mg per day for most adults.

Magnesium Deficiency

Some older surveys estimate that approximately half of the people in western cultures like the United States and Europe are deficient in magnesium.

A true magnesium deficiency, or hypomagnesemia, is defined as blood levels of less than 0.75 mmol/L.

Early signs of magnesium deficiency often present as things like nausea, fatigue, loss of appetite, and vomiting.

More pronounced symptoms may include muscle cramps, tremors, and even seizures.

Being deficient in magnesium can also result in a number of health problems over time.

Some studies have found an association between low magnesium levels and a higher risk for type 2 diabetes, Alzheimer’s dementia, and heart disease.

If you know you have a magnesium deficiency, correcting it has been shown to offer health improvements.

However, magnesium has a half-life of 42 days. This means that it might take longer to correct a deficiency and require ongoing supplementation in addition to a magnesium-rich diet.

Benefits of Magnesium Supplementation

Getting enough magnesium helps ensure that your body can continue all of its normal functions. Magnesium supplements may also offer unique benefits of their own for some people.

May Offer Heart Health Benefits

Research suggests that having subclinical magnesium deficiency is associated with an increased risk for chronic diseases, including cardiovascular disease.

This means having a nutrient deficiency that’s so mild that it’s not caught by virtual exams and doesn’t cause noticeable symptoms.

Magnesium supplements may help reduce high blood pressure, which is a known risk factor for developing heart disease and stroke.

One 2012 meta-analysis concluded that although the benefit is mild in most cases, there’s enough clinical significance to research further the use of magnesium for lowering blood pressure.

Some studies have suggested that people who consume more magnesium may have a lower risk for heart disease.

Benefits to blood pressure have been seen, especially when consuming more magnesium is combined with higher potassium and reduced sodium intake.

Other research has found magnesium supplementation to be worthwhile in the treatment of metabolic syndrome when someone has magnesium deficiency and a cluster of conditions (like high blood pressure, high triglycerides, and low HDL “good” cholesterol) that puts them at higher risk for heart disease.

Summary

Magnesium supplementation may be helpful in reducing certain risk factors for heart disease, such as high blood pressure, particularly when someone is deficient.

May Help Regulate Blood Sugar

One of the major roles of magnesium in your body is to help keep blood sugar levels in a normal range.

Plus, magnesium deficiency is often identified among people with type 2 diabetes.

It may be especially prevalent among people who also suffer from severe retinopathy.

One 1998 clinical trial of people with poorly controlled type 2 diabetes who were supplemented with 1000 mg per day of magnesium oxide found their blood sugar control improved within one month.

Many studies since then have also found that magnesium supplementation has some beneficial effect on the blood sugar control of people with type 2 diabetes, though more research is needed.

However, some studies have found magnesium supplementation is more effective at improving insulin sensitivity than glucose control among people with type 2 diabetes.

Summary

Magnesium supplementation may help improve blood sugar control and insulin sensitivity, especially among people with type 2 diabetes who have a magnesium deficiency.

May Benefit Bone Health

Having tight control over how much magnesium is in your body appears to be associated with bone health.

In fact, both having too much and too little magnesium can have negative effects on your bones.

When magnesium deficiency is present, as is more often the case, it can actually cause crystallization on bone cells, influencing parathyroid hormone secretion and encouraging low-grade inflammation.

This results in osteopenia and, if left untreated, eventually can become osteoporosis.

One theory is that magnesium deficiency might prevent osteoblasts from doing their job in building bones and instead promote the activity of osteoclasts to break down bones.

Summary

Having enough magnesium in your body is necessary to support healthy bones. Magnesium deficiency may actually lead to degradation of bone mineral density, increasing your risk for osteopenia and osteoporosis.

May Help Reduce Migraines

As if having migraines wasn’t annoying enough, trying to figure out what’s triggering yours can be a challenge in itself.

Studies on headaches and migraines have found that people who suffer from them often have low levels of magnesium, suggesting that magnesium deficiency is involved in the pathogenesis of severe headaches.

One 2018 review examined five clinical trials, finding that magnesium supplementation could be considered a possibly effective preventive agent for migraines and may be worth trying.

The authors found that 600 mg of magnesium di-citrate seemed to be a safe and effective option for preventing migraines.

In addition to headaches and migraines, magnesium supplementation has been found helpful in alleviating pain related to fibromyalgia and menstrual symptoms, further demonstrating its ability to act as an analgesic.

Summary

People with chronic migraines are commonly found to have low levels of magnesium. Some studies have found success in alleviating migraine frequency and pain severity with magnesium supplementation.

Dietary Sources

The first place to find magnesium is in various foods, many of which you may already eat.

While small amounts of magnesium can be found in fish, meat, and dairy products, most are found in whole plant foods.

Some foods have been fortified to contain magnesium, like certain breakfast cereals.

Some of the best sources of dietary magnesium include beans, peas, lentils, green leafy vegetables, nuts, and seeds.

Below are a few examples of magnesium-rich foods and how much they can provide:

  • Roasted pumpkin seeds, 1 ounce: 136 mg
  • Chia seeds, 1 ounce: 111 mg
  • Dry roasted almonds, 1 ounce: 80 mg
  • Boiled spinach, 1/2 cup: 78 mg
  • Soy milk, 1 cup: 61 mg
  • Cooked black beans, 1/2 cup: 60 mg
  • Peanut butter, 2 tablespoons: 49 mg
  • Cooked brown rice, 1/2 cup: 42 mg
  • Banana, 1 medium: 32 mg
  • Atlantic salmon, 3 ounces: 26 mg
  • Whole wheat bread, 1 slice: 23 mg

Eating a wide variety of these foods is a good way to meet your needs for this mineral. Think about your own diet. Do you eat many of these foods regularly?

Who Needs a Magnesium Supplement?

While many foods can contain magnesium, some people find it easier to meet their needs by adding supplements.

Teenagers appear to be at a higher risk for magnesium deficiency, likely due to inadequate dietary intake.

Magnesium absorption also appears to decline with age. How much of the mineral your body actually uses may decline by more than 30% as you age.

Additionally, if you eat a diet high in processed foods and low in whole plant foods, you may be at a higher risk of not getting enough magnesium.

Some studies suggest that food processing, like making white flour or rice, can actually reduce natural magnesium content by 300–400%.

Of course, other factors can play a role in how well various forms of magnesium are absorbed that may lead to deficiency.

For instance, there’s some evidence that rare genetic mutations can put families at a higher risk for magnesium deficiency that’s difficult to correct.

If you fall into one of these categories, you may be considering adding a magnesium supplement to your routine.

Let’s talk about what to look for when you begin your search.

Types of Magnesium Supplements

One of the first things you’ll likely notice when looking for a magnesium supplement is that they come in a number of forms, or different magnesium salts.

The main difference between the forms is that some may be better absorbed by the body than others, making them more effective for boosting magnesium levels.

Still, some research has found no significant differences between the bioavailability of magnesium supplement types.

Some of the most absorbable forms of magnesium include:

  • Magnesium citrate
  • Magnesium lactate
  • Magnesium aspartate
  • Magnesium chloride
  • Magnesium malate
  • Magnesium taurate

However, their best uses can vary. Below are the most commonly available magnesium salts sold as supplements, including what we know about their efficacy.

Magnesium oxide: While this is one of the most frequently used forms, the bioavailability of magnesium oxide is generally found to be poor. For instance, regular tablets have around a 4% absorption rate, while effervescent tablets are slightly better with an 8% absorption rate.

Magnesium hydroxide: This form is often used as an antacid and a laxative, increasing the water content and weight of stool to help ease constipation. Magnesium hydroxide works best in this way, rather than to correct a magnesium deficiency, because it’s not absorbed well.

Magnesium chloride, lactate, and aspartate: These forms have been observed to have similar high bioavailability.

Magnesium citrate: This form appears to offer medium bioavailability. For comparison, it’s more soluble and better absorbed than magnesium oxide.

How to Choose a Magnesium Supplement

When you’re looking for the right magnesium supplement for your lifestyle, there are a few things to keep in mind. Consider the shopping tips below when making your decision.

Form

As described above, there are a number of magnesium salt forms sold as supplements.

Which form of magnesium makes the most sense for you depends on things like absorption rates and your reason for using a magnesium supplement.

A 2019 study compared the timing and bioavailability of various magnesium compounds to see which worked best.

The researchers gave a dose of 400 mg/70 kg magnesium supplements to rats and observed the time-dependent absorption, tissue penetration, and any resulting behavioral effects.

Overall, they found that magnesium oxalate and magnesium citrate have the lowest bioavailability, even though they’re among the most commonly prescribed forms.

On the other hand, magnesium acetyl taurate was found to have rapid absorption, easily pass the blood-brain barrier, and have a high concentration in brain tissue.

This form was also observed to help reduce indicators of anxiety.

Additionally, amounts of magnesium malate remained high in the blood for a long period.

Certain forms of magnesium are used more commonly for certain purposes or conditions and may not be relevant for general use.

For instance, magnesium citrate is often used in the treatment and prevention of certain types of kidney stones.

Magnesium orotate may be useful in heart failure. Magnesium glycinate or taurate have been used in depression.

Magnesium mandelate is sometimes used as a urinary antiseptic. Magnesium salicylate is used in the management of rheumatoid arthritis.

Lastly, forms of magnesium that are more soluble, or can dissolve in liquid, are better absorbed in the gut.

You might want to look for magnesium supplements that come in powdered form and can be stirred into water to drink, for example, rather than a tablet to swallow.

Dosing

The recommended daily dose for magnesium falls between 200–400 mg per day for most adults.

However, the tolerable upper limit (UL) for magnesium is 350 mg per day in supplemental form, established by the Institute of Medicine.

This amount is known to cause no major side effects.

At higher doses, some may experience cramping, nausea, and diarrhea.

Be aware of whether other supplements you take may contain magnesium, such as a multivitamin with minerals, which could put you over the daily recommended limit.

Avoid higher doses unless otherwise directed by your healthcare provider.

Purpose

Not everyone needs a magnesium supplement or would necessarily benefit from taking one. What’s the reason you’re looking into adding one?

While some magnesium supplements are intended to provide additional amounts of the mineral to your diet or correct a deficiency, others have been designed with another purpose in mind.

For example, some magnesium supplements are marketed to help provide a sense of calm, alleviate migraines, target constipation, or help reduce leg cramps.

Some of these products may be formulated with other ingredients designed for these specific purposes, so be sure to read the supplement facts panel.

Third-Party Testing

As with all dietary supplements, I recommend looking for one that bears an official seal from a third-party testing seal. Some examples include ConsumerLab, USP, UL, and NSF International.

When a supplement has one of these seals, it indicates the brand has invested in unbiased, independent testing for safety, quality, and purity.

In other words, the product is free from harmful levels of contaminants and has been verified to contain what it claims on its label.

If you’re choosing between two comparable magnesium supplements, I’d suggest going with the one that has a third-party testing seal.

Safety and Side Effects

When consumed naturally through food, there’s no reason to be concerned about getting too much magnesium, as healthy people can get rid of excess through normal excretion.

However, magnesium in supplemental form can exceed the recommended daily limit and become potentially harmful.

The tolerable upper limit for magnesium is 350 mg per day from supplements for individuals aged 9 years and above.

Kids aged 1–3 years old shouldn’t get more than 65 mg per day, and kids 4–8 years old should not exceed 110 mg per day.

The most common side effects from getting too much supplemental magnesium are gastrointestinal complaints, such as abdominal cramping, nausea, and diarrhea.

Extremely high intake can cause irregular heartbeat and heart attack.

Magnesium supplements can also interact with certain medications.

Magnesium can prevent the proper absorption of bisphosphonates, which are used to treat degenerative bone disease osteoporosis.

It can also reduce the absorption of certain antibiotics if taken too closely together.

Diuretics may alter magnesium losses through normal urine excretion, and very high doses of supplemental zinc can alter how well your body regulates magnesium levels.

Lastly, prolonged use of some prescription acid reflux or peptic ulcer drugs may reduce overall magnesium levels in your body.

Always speak to your healthcare provider before starting a magnesium supplement.

The Bottom Line

Magnesium is an essential nutrient with a number of important roles in maintaining your health and the function of your body.

While magnesium can be found in various foods, particularly plants, nearly half of all people don’t get enough of it.

In instances where magnesium may be lacking in the diet, a magnesium supplement may be beneficial.

When choosing the best supplement for you, it’s a good idea to consider the most bioavailable forms, your purpose for using it, the dosage, and whether the option bears a third-party testing seal.

As with all supplements, be sure to speak to your healthcare provider before adding a magnesium supplement to your routine to make sure it’s safe and appropriate for you.

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