The Best Magnesium Supplements

Why you might be Magnesium depeleted

Soil depletion is the main culprit. The silent epidemic

Most Americans (50-85%) don’t get the recommended daily intake of magnesium, according to the National Academy of Science leading to magnesium deficiency (Ref: Mag2). This may contribute to diseases such as high blood pressure, diabetes, and neurologic disease. A 2013 meta-analysis finds that lower dietary magnesium intake is correlated to higher risk of heart disease (Ref: Circulating and dietary magnesium and risk of cardiovascular disease: a systematic review and meta-analysis of prospective studies

Am J Clin Nutr, 98 (2013), pp. 160-173). Eating a daily magnesium supplement is also correlated to a 22% reduced risk of ischemic events (Ref: Urinary and plasma magnesium and risk of ischemic heart disease

Am J Clin Nutr, 97 (2013), pp. 1299-1306). In this article, we discuss why magnesium deficiency is so common and the best supplements to take. Note that this article is NOT sponsored, and I am not recommending any specific brands

What is Magnesium?

Abundant magnesium deposits were discovered near the ancient Greek city of Magnesia from which the word is derived. Magnesium is a trace mineral and the fourth most abundant cation (positive ion) in the body. Foods contain many micro-nutrients - including the vitamins (A, B, C, D, E, K etc.) and minerals (calcium, iron, magnesium). They are called micro-nutrients because the physical amount is very small. Nevertheless, they are critical for normal body functions as they are a key component of the body’s enzymes and hormones.

Magnesium forms the central part of chlorophyll, and is critical in plant function, just as iron is critical in hemoglobin. Plants are therefore the major source of dietary magnesium, although seafood also is a good source (from the minerals in sea water). Good sources of magnesium include dark chocolate, nuts, seeds, legumes, tofu and some fruits like avocado.

Our bones contain the majority (60%) of the body’s magnesium with 20% in skeletal muscle and 19% in other organs like the liver. Very little is found in the blood, so the blood concentration of magnesium (measured by the standard blood test) is a poor reflection of the body’s store of magnesium. You can be very magnesium deficient but still have a normal blood magnesium level.

What happens when you are low in Magnesium?

Magnesium is a critical co-factor for many enzymatic functioning for about 80% of known metabolic functions. Symptoms of low magnesium include constipation, muscle cramping, muscle twitching, tingling, irritability and if severe, seizures, abnormal heart rhythms (arrhythmias) and coronary spasm. Magnesium is particularly important for blood pressure regulation, muscle and nerve function. Because the symptoms are so non-specific, it is easy to miss magnesium deficiency. If you don’t look for it, you’ll easily miss it.

Why are most people not getting enough Magnesium?

1.     Declining magnesium in the Food Supply

Most of the magnesium we get comes from plant foods. But the fruits and vegetables grown today contain an estimated 90% less magnesium compared to previous years. The soil used to grow crops has become steadily depleted of magnesium. Industrial scale farming practices are largely to blame.

To deliver super-sized crop yields on the least amount of land, industrial farms apply generous amounts of chemical fertilizer. The three main components of fertilizer are known as NPK - Nitrogen, Phosphorus and Potassium. Organic fertilizers like manure will contain other trace minerals like magnesium, but the chemically synthesized fertilizers typically used in factory farming do not. More and more crops are growing with less and less magnesium in the soil.

2.     Refined Foods

The modern American diet, on average, contains about 60% refined foods. The refining and processing of foods depletes magnesium. For example, refining of wheat to flour (82% loss), rice to polished rice (83%), and corn to starch (97%) (Ref: Marrier JR (1986) Magnesium content of the food supply in the modern day world. Magnesium 5:1–8)

3.     Softening/ Filtering of Water

Magnesium in the water supplies approximately 10% of the daily recommended intake. Hard water, full of calcium and magnesium causes problems for pipes because it tends to develop hard deposits called scale. Municipal water treatment often removes these minerals, softening the water to reduce this problem. This also reduces the amount of magnesium we ingest.

Fluoride is added to the drinking water in many municipalities to prevent cavities. The fluoride may bind to ingested magnesium to form insoluble precipitates that are not absorbed by the GI tract.

4.     Soft Drinks/ Caffeine/ Alcohol

Soft drinks contain high levels of phosphoric acid, which can bind magnesium in the gut to form insoluble precipitates.  which are not absorbed.

Caffeine and alcohol can increase magnesium excretion in the urine. Alcohol increases urinary loss of magnesium by up to 260%. Alcoholics are particularly prone to magnesium depletion as their diet also tends to be very poor.

5.     Medical Conditions/ Medications

People with diabetes are at risk of magnesium deficiency because of high urinary losses. The high blood glucose may increase urine flow, dragging magnesium along with it. Diuretics (sometimes called water pills), a common medication for high blood pressure and heart failure also increases the loss of magnesium in the urine

Chronic diarrhea or gastrointestinal disease, such as Crohn’s disease, celiac disease or colitis impairs magnesium absorption leading to increased risk of magnesium deficiency.

Does Taking Magnesium supplements make a Difference?

Maybe.

Correlation studies, as noted above suggest that supplements can improve health, especially with regards to risk of heart disease. But this is not a high level of evidence. Randomized controlled trials (RCT) are better suited to determine benefits and there are only a few small studies, although they are suggest some benefits for vascular health and inflammation.

A 2016 RCT compared 52 overweight individuals to magnesium supplementation versus placebo over 24 weeks. The primary outcome was the change in carotid-femoral pulse wave velocity, a well validated measurement of how stiff an artery is. The stiffer the artery, the faster the pressure wave moves across the blood vessels and this can be measured non-invasively. Stiff arteries contribute to arteriosclerosis which leads to vascular diseases like heart disease and strokes.

In this study, the pulse wave velocity decreased in the magnesium group but not placebo and the magnitude of decrease could be extrapolated into a 7% decrease in vascular events. This, however, is a small study and done over a relatively short period of time, so it is far from conclusive. 

A 2022 meta-analysis looked at all the RCTs done looking at the effects of magnesium supplementation on inflammatory markers like C reactive protein (CRP).

The magnesium group also had an increase in nitric oxide (NO) a key vasodilator. Higher levels of nitric oxide tend to relax the blood vessels and make them more pliable, therefore less likely to spasm and block.

How to Get Enough Magnesium

1.     Transdermal (Through the Skin) Absorption

Magnesium can be absorbed directly through prolonged contact with the skin. More specifically, recent studies show that much of the magnesium is absorbed through the hair follicle rather than directly through the skin. Traditional therapies like Epsom salt baths or soaking in mineral waters like the Dead Sea suggest potential benefits. Epsom salts are salts of magnesium which can be added to your bath. Soaking for half an hour or more may allow that magnesium to be absorbed. There are also numerous preparations like magnesium oil that you can spray on the skin without the need to sit in the bath.

However, how much magnesium gets absorbed is hard to know. It’s likely highly variable from person to person, and there are insufficient studies to say that this is a reliable way to supplement magnesium. Oral supplements are more reliable and better studied.

2.     Oral Supplementation

Magnesium isn’t easily absorbed in the intestines because it has a densely charged positive charge which attracts a tight double shell of water molecules around it. This makes the magnesium molecule very large and hard to absorb compared to calcium for example.

There are two types of oral supplements - inorganic and organic salts of magnesium. Inorganic salts like magnesium oxide generally have lots of elemental magnesium, but it comes in a form that is poorly soluble and not easily absorbed by the intestines. If you eat a lot of magnesium, but most of it comes out in your stools, well, let’s just say that offers few benefits.

The most common inorganic magnesium is magnesium oxide. It is the cheapest and probably the least effective. Many lower priced supplements contain magnesium oxide. Beware of supplements that contain a blend that include magnesium oxide because many will not disclose the percentage of oxide versus other magnesium salts.

The organic salts of magnesium contain less elemental magnesium, so they look like a smaller dose, but these salts are more soluble and easily absorbed. The difference between organic and inorganic salts is striking.

Supplements with organic magnesium salts improve absorption by more than 10-fold compared to magnesium oxide. This translates directly into a higher level of magnesium in the blood.

When you are shopping for magnesium supplements, avoid the cheaper magnesium oxide with its high elemental magnesium. With its low absorption rate, you might as well sprinkle that magnesium directly into the toilet after going #2. It’ll be the same end result. Look for supplements that contain organic salts like magnesium glycerophosphate, citrate, glycinate and carbonate.

Dr. Jason Fung

For more, check out my YouTube channel, online community and coaching programs at TheFastingMethod.com and my books