Magnesium Forms Compared: Which Type Is Best Absorbed?

Magnesium is an essential nutrient used for over 300 processes in the body, and is responsible for everything from muscle and nerve function, to blood sugar control, to blood pressure regulation, to the synthesis of DNA. It's an incredibly important mineral, and adequate intake is critical to long-term health.

Magnesium supplements come in many different forms. Citrate? Glycinate? Taurate? Which one is best absorbed, which should be avoided, and what does the science say about this essential mineral? Read on to find out more.

The Basics of Magnesium

There is a separate post on this blog focused on magnesium basics — covering recommended daily intake levels and the foods highest in magnesium. That information is available here.

As a baseline:

• Magnesium needs increase throughout life until adulthood, at which point men need around 400 mg per day, while women need around 300; pregnant women need more to stay healthy.
• Magnesium is found mostly in plant-based foods, with pumpkin and chia seeds containing the most. An ounce of pumpkin seeds has 156 mg of magnesium on average; an ounce of chia has 111 mg, and an ounce of almonds has 80. Half a cup of spinach has 78 mg.
• Magnesium deficiency is common due to the average American diet, and estimates say that as much as half of all Americans are sub-clinically deficient in magnesium. This video explains magnesium deficiency in greater detail.

Unless a diet is already heavily focused on plant-based whole foods, there is a real chance of being at least mildly deficient in magnesium. It's no wonder that many foods, like cereals, are fortified with additional magnesium and that magnesium supplements are plentiful.

The Benefits of Magnesium Supplements

If millions of people are chronically low on magnesium, surely there are benefits to taking magnesium supplements, right? Well, not so fast. Many studies have shown benefits to taking magnesium, but there are some questions that need to be asked which may temper expectations.

For one thing, it's not clear whether or not the benefits of magnesium supplements come from taking extra magnesium over an already healthy diet or if the benefits all come from addressing a deficiency. It's entirely possible that people with magnesium-rich diets won't benefit at all from additional magnesium, but the science should do the talking on that one.

The Problem with Magnesium Deficiency

Estimates place magnesium deficiency as affecting as much as 50% of the American population. These are just estimates, however, for two reasons.

The first is that the effects of sub-clinical magnesium deficiency are often minor and difficult to attribute specifically to magnesium. Often, people with magnesium deficiency aren't eating healthy diets and are deficient in a range of micronutrients and vitamins.

The second is that magnesium deficiency, specifically, is very hard to diagnose. Symptomatic magnesium deficiency is extremely rare, and the symptoms are very generic (like nausea, vomiting, fatigue, and weakness) when they do occur.

Moreover, there are no effective tests to check magnesium levels. Blood tests aren't effective because of how the body retains magnesium, bone tests are very invasive and not recommended, and urine tests aren't reliable.

Looking at Magnesium Studies

A study from 2010, which observed over 14,000 people, showed that higher levels of magnesium intake were associated with a 40% reduction in sudden heart death, after adjusting for variables. Another study from just three years later looked at 300,000 people and showed a similar effect, of a 30% reduction in heart disease risk. A third study that looked at 240,000 people showed an association between higher magnesium and a lower risk of stroke.

These are just a few of the studies published on magnesium over the last decade and change. Additional studies have shown correlations between higher magnesium intake and reduced risk of ailments like metabolic syndrome, diabetes, high blood pressure, high cholesterol, and more.

It is important to temper expectations with these kinds of studies. A correlation between higher magnesium intake and lower risk of disease does not necessarily mean that magnesium causes that beneficial effect. There could very well be another factor at play that isn't as easily observed. There are relatively few "gold standard" randomly controlled human trials proving causation.

The actual human studies that have been performed are also both very small and often contradictory. For example, this study of 200 people found that magnesium was beneficial for diabetes; this one of 50 people did not.

Should You Take Magnesium Supplements?

This is a difficult question to answer.

Magnesium is undeniably critical to the proper function of the body and to long-term health. However, without extreme deficiency and specific diagnosis, there's no reliable way to tell if someone is deficient. It is possible to examine the diet, calculate magnesium intake, and check it against the RDI, but even that approach has a significant margin for error.

When choosing a form of magnesium for a daily supplement, the form matters. For example, some formulations use taurinate — a combination of magnesium and the amino acid taurine — at a lower elemental magnesium dose (around 126 mg), the reasoning being that both the magnesium component and the taurine component provide value, without needing to push elemental magnesium doses to high levels to see a benefit. Others prefer glycinate for its gentle tolerability profile.

Magnesium supplements on the market range from 200 mg to a whopping 2,000 mg per serving. Most standard supplements are in the 200–500 mg range. This is more reasonable but still runs the risk of megadosing when dietary intake is not also factored in. The main evidence-based caution is to avoid megadosing on any mineral outside of a doctor's explicit guidance. Always consult a healthcare professional to determine what, if any, magnesium supplementation is appropriate given individual health and nutritional circumstances.

Which Forms of Magnesium are Best and Worst?

Magnesium comes in many different forms. Each form combines elemental magnesium with another nutrient, and the way they interact with the body can vary dramatically based on these differences.

It's important to note that there's not necessarily a single "best" form of magnesium. Different forms have different benefits and work in different ways. The right choice depends on the specific goal — absorption, sleep support, digestive tolerance, or cost.

Magnesium Citrate

First up is magnesium citrate, which is one of the more common forms of magnesium supplement. It's a combination of magnesium and citric acid. Citrate is commonly recommended as a treatment for constipation due to its ability to act as a laxative. According to one small study, it's more bioavailable than magnesium oxide, meaning it may help deliver more magnesium to the body.

Because of the laxative effect, the side effects of magnesium citrate are, at best, annoying and disruptive, so it's usually prescribed for constipation and not much else.

Magnesium L-Threonate

A combination of magnesium and threonic acid, a byproduct of vitamin C breakdown, magnesium l-threonate is one of the more expensive but potentially promising forms of magnesium.

Some small studies have indicated that it's the best form for passing the blood-brain barrier, so it may have some benefits for mental health, depression, anxiety, and sleep quality. However, there are relatively few human trials to back up these claims. It's an active area of research, and a dedicated post covers this form in more detail for those who want to go deeper.

Magnesium Oxide

Magnesium oxide is one of the most common forms of magnesium found in nature, as it's simply a combination of magnesium and oxygen. It was one of the first widespread magnesium supplements, but it's relatively poorly absorbed compared to other forms of magnesium.

Some studies have indicated that it may help with heartburn, indigestion, constipation, and migraines, though, as with all forms of magnesium, more research is required to prove these claims. Due to the poor absorption, it may not be viable for meaningfully raising body magnesium levels, and it's unlikely that more studies will be forthcoming any time soon.

Magnesium Glycinate

Magnesium glycinate is a combination of magnesium and glycine, the amino acid. The body readily absorbs amino acid-bound minerals, making glycinate one of the better-absorbed forms of magnesium. It is commonly studied in the context of inflammation, cardiovascular health, migraines, diabetes, and sleep quality. Some of these effects have been demonstrated in animal studies, but have not yet been fully reflected in human trials.

Like the other forms of magnesium, there are relatively few studies about its effects, or whether or not they extend beyond treating an underlying deficiency.

Magnesium Chloride

A combination of magnesium and chlorine, this is a sort of middle-ground version of magnesium. It's reasonably well absorbed, and the list of benefits is similar to other forms, such as helping with heartburn, constipation, and low magnesium levels.

Again, few studies have definitively proven these benefits. It's also a relatively simple form of magnesium, so it doesn't combine the benefits of a co-ingredient the way l-threonate or taurinate do.

Magnesium Taurinate

Magnesium taurinate, also known as magnesium taurate, combines magnesium with taurine, another amino acid. Taurine is well-studied and has several tangible benefits that have been proven in human clinical trials. A dedicated video on taurine covers the evidence in detail.

Magnesium taurinate may combine the benefits of taurine with the added magnesium to address deficiency. The appeal of this form is that it delivers two well-studied nutrients — magnesium and taurine — in a single compound.

Magnesium Lactate

Lactic acid combines with magnesium to form magnesium lactate. Lactic acid is used as a preservative in foods, and this form of magnesium is usually found as an ingredient meant to fortify foods. It is relatively rare as a stand-alone supplement.

One small study observed that a slow-release magnesium lactate supplement worked better with fewer digestive side effects than other magnesium supplements. Research also suggests a possible positive effect on stress and anxiety, but that requires more study to establish.

Magnesium Malate

Malic acid is a natural acid found in foods like fruit and is added to foods for a sour flavoring. Magnesium malate is well-absorbed and reportedly gentler on the digestive system than some other forms of magnesium, making it similar to magnesium lactate in that regard.

This is one of the forms most commonly found in 1,000–2,000 mg doses, which represents a level to approach with caution given the risk of exceeding safe daily intake when dietary magnesium is also factored in.

Magnesium Sulfate

Magnesium, combined with both oxygen and sulfur, forms sulfate. This is very rarely found as a supplement because it's one of the few forms of magnesium that can be dangerous in large doses.

Instead, it is widely recognized under the common name Epsom Salt, where it's used as a relaxation aid when added to a bath.

Magnesium Orotate

Magnesium orotate is a combination with orotic acid, which is used in the synthesis of DNA. Some studies have shown that it is better absorbed than many other forms of magnesium and has fewer digestive side effects.

It may also support heart health, so it's frequently seen as an athletic supplement. The biggest downside is that it's significantly more expensive than other forms of magnesium.

Which Form of Magnesium is the Winner?

In general, it depends on the goal.

For general daily magnesium intake, magnesium taurinate is a compelling choice because it delivers both magnesium and taurine — a well-studied amino acid — in one compound.

Magnesium glycinate is also a strong option for those seeking a well-absorbed, easy-on-the-digestive-system form that isn't overly expensive. For sleep support specifically, the bisglycinate (fully chelated) form is well tolerated and commonly included in evidence-based sleep formulations.

As always, speaking to a healthcare professional to determine what, if any, magnesium supplements are appropriate is the best starting point given individual health concerns and nutritional profile.

Sources:

1. National Institutes of Health Office of Dietary Supplements Magnesium Consumer Fact Sheet: https://ods.od.nih.gov/factsheets/Magnesium-Consumer/
2. National Institutes of Health Office of Dietary Supplements Magnesium Fact Sheet for Health Professionals: https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/
3. Subclinical magnesium deficiency: a principal driver of cardiovascular disease and a public health crisis: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5786912/
4. Serum Magnesium and Risk of Sudden Cardiac Death in the Atherosclerosis Risk in Communities (ARIC) Study: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2939007/
5. Circulating and dietary magnesium and risk of cardiovascular disease: a systematic review and meta-analysis of prospective studies: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3683817/
6. Dietary magnesium intake and risk of stroke: a meta-analysis of prospective studies: https://pubmed.ncbi.nlm.nih.gov/22205313/
7. Researchers Find Low Magnesium Levels Make Vitamin D Ineffective: https://osteopathic.org/2018/02/26/researchers-find-low-magnesium-levels-make-vitamin-d-ineffective/
8. Magnesium Deficiency Questionnaire: A New Non-Invasive Magnesium Deficiency Screening Tool Developed Using Real-World Data from Four Observational Studies: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7400907/
9. Oral Magnesium Supplementation and Metabolic Syndrome: A Randomized Double-Blind Placebo-Controlled Clinical Trial: https://pubmed.ncbi.nlm.nih.gov/29793665/
10. Oral magnesium supplementation in insulin-requiring Type 2 diabetic patients: https://pubmed.ncbi.nlm.nih.gov/9632126/
11. Intestinal Absorption and Factors Influencing Bioavailability of Magnesium-An Update: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5652077/
12. The Relationship between Plasma Taurine Levels and Diabetic Complications in Patients with Type 2 Diabetes Mellitus: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6468751/
13. Assessment of bioavailability of Mg from Mg citrate and Mg oxide by measuring urinary excretion in Mg-saturated subjects: https://pubmed.ncbi.nlm.nih.gov/32162607/
14. National Institute of Health – StatPearls – Magnesium Sulfate: https://www.ncbi.nlm.nih.gov/books/NBK554553/