By Dr. Mercola
When it comes to heart health, one of the most influential nutrients is magnesium. While required for the healthy function of most cells in your body, magnesium is particularly important for your heart, kidneys and muscles.
As far back as 1937, researchers warned that low magnesium levels pose serious risks to the heart, and that it may actually be the most significant predictor of heart disease.1 More recent research suggests even subclinical magnesium deficiency can compromise your cardiovascular health.2
Importantly, your mitochondria require magnesium to produce ATP. It's also required for the metabolic function of your cells and the activation of vitamin D.3,4 All of these are important for healthy heart function.
It also supports heart health by relaxing your blood vessels, normalizing blood pressure, lowering inflammation and supporting endothelial function (the cells' lining the interior of your blood vessels).5
Hard Water Linked to Better Heart Health
To celebrate its 175th anniversary, Scientific American recently took a look back into its archives, publishing a short summary of research presented in its June 1969 issue:6
"Several studies in the past decade have suggested that the death rate from coronary disease is inversely correlated with the hardness of the local water supply: the harder the water, the lower the coronary rate.
A study7 recently published in the New England Journal of Medicine reports evidence that the excess coronary deaths in soft-water areas are almost entirely sudden deaths …"
By reviewing the death certificates of 55,000 individuals who died from heart-related issues in Ontario during 1967, and then correlating the deaths according to the hardness of the local water supply, the Canadian researchers were able to conclude that people drinking soft water on a regular basis were more susceptible to lethal arrhythmias (irregular heartbeat). What might explain this curious correlation?
One theory has focused on the magnesium level found in the water.8 Soft water is lower in magnesium than hard water, thus making you more prone to magnesium deficiency. (The very definition of hard water is that it contains a high concentration of dissolved metals — calcium and magnesium in particular.9,10)
According to a 2002 study,11 magnesium-rich mineral water can contribute between 6% and 17% of your total daily magnesium intake. That said, a 2013 paper12 in the International Journal of Preventive Medicine points out that the exact mechanisms responsible for the relationship often found between harder water and lower cardiovascular risk has yet to be ascertained.
The higher magnesium level in hard water appears to be a promising hypothesis, though, and several studies point to magnesium-rich water being an important factor. As noted in the International Journal of Preventive Medicine, which cites a number of such studies (as well as some in which this relationship was not found):13
"In a Swedish study, the skeletal muscle magnesium levels were a significantly higher in persons living in an area with a higher water magnesium."
Even Subclinical Magnesium Deficiency Can Be Problematic
As mentioned, magnesium supports heart health through a number of different mechanisms.14 For starters, it combats inflammation, which helps prevent high blood pressure and hardening of your arteries. It also improves blood flow by relaxing your arteries and preventing your blood from thickening.
Magnesium also plays a role in the creation of adenosine triphosphate (ATP), the energy currency of your body.15,16 Needless to say, without sufficient energy, cellular functions throughout your body will suffer, creating a cascade of dysfunction. Your heart in particular, being a very heavy energy user, needs sufficient amounts of ATP to function properly.
Magnesium also affects your mitochondrial function and health, as it's required both for increasing the number of mitochondria in your cells and for increasing mitochondrial efficiency.
Basic effects such as these can account for why magnesium insufficiency has been linked to a higher risk for high blood pressure,17 cardiovascular disease, arrhythmias, stroke18 and sudden cardiac death.19
A 2018 paper20 in the Open Heart journal also warns that even subclinical deficiency can result in heart problems, and that most people need at least 300 milligrams more magnesium per day than the current recommended dietary allowance prescribes. According to the authors:
"… While the recommended … dietary allowance for magnesium (between 300 and 420 mg /day for most people) may prevent frank magnesium deficiency, it is unlikely to provide optimal health and longevity, which should be the ultimate goal."
The theory that we may need more magnesium than is currently recognized is also supported by a 2016 meta-analysis,21 in which all-cause mortality was lowered by 10% simply by increasing magnesium intake by 100 mg per day.
Magnesium Is Important for Brain Health Too
Magnesium is also important for brain health and the prevention of dementia. Memory impairment occurs when the connections (synapses) between brain cells diminish. While many factors can come into play, magnesium is an important one. As noted by Dr. David Perlmutter, a neurologist and fellow of the American College of Nutrition:22
"It has now been discovered that magnesium is a critical player in the activation of nerve channels that are involved in synaptic plasticity. That means that magnesium is critical for the physiological events that are fundamental to the processes of learning and memory.
As it turns out, one form of magnesium, magnesium threonate, has the unique ability to permeate the brain and enhance the receptors that are involved in this process."
The specific brain benefits of magnesium threonate were demonstrated in a 2010 study23 published in the journal Neuron, which found this form of magnesium enhanced "learning abilities, working memory, and short- and long-term memory in rats." According to the authors:24
"Our findings suggest that an increase in brain magnesium enhances both short-term synaptic facilitation and long-term potentiation and improves learning and memory functions."
Magnesium is also a well-recognized stress reliever,25 and by catalyzing mood-regulating neurotransmitters like serotonin, it helps prevent anxiety and depression.26
Research27 published in 2015 found a significant association between very low magnesium intake and depression, especially in younger adults. A study28 published in PLOS ONE demonstrated magnesium supplementation improved mild-to-moderate depression in adults, with beneficial effects occurring within two weeks of treatment.
How to Assess Your Magnesium Status
When it comes to measuring your magnesium level, your best bet is an RBC magnesium test, which measures the amount of magnesium in your red blood cells. Tracking any symptoms of magnesium deficiency is also recommended, as your need may be higher or lower depending on your lifestyle and health status.
Common signs and symptoms of magnesium insufficiency include but are not limited to the following.29,30 A more exhaustive symptom's list can be found in Dr. Carolyn Dean's blog post, "Gauging Magnesium Deficiency Symptoms."31
- Seizures, muscle spasms (especially "charley horses" or spasms in your calf muscle that happen when you stretch your leg), eye twitches and or numbness or tingling in your extremities
- Insulin resistance
- High blood pressure, heart arrhythmias and/or coronary spasms
- Increased number of headaches and/or migraines
- Low energy, fatigue and/or loss of appetite
The "Trousseau sign"32 can also be used to assess your magnesium status. To check for this sign, a blood pressure cuff is inflated around your arm. The pressure should be greater than your systolic blood pressure and maintained for three minutes.
By occluding the brachial artery in your arm, spasms in your hand and forearm muscles are induced. If you are magnesium deficient, the lack of blood flow will cause your wrist and metacarpophalangeal joint to flex and your fingers to adduct. For a picture of this hand/wrist position, see Figure 1 in the paper "Trousseau Sign in Hypocalcemia."33
Would You Benefit From Magnesium Supplementation?
A number of studies suggest magnesium insufficiency or deficiency are extremely common, both among adults34 and teens,35 in part due to the fact that most people eat a plant-deficient diet. Magnesium is actually part of the chlorophyll molecule responsible for the plant's green color.
However, even if you eat plenty of greens, you may still not get enough, thanks to most soils being so depleted of minerals. Your body's ability to absorb magnesium is also dependent on having sufficient amounts of selenium, parathyroid hormone and vitamins B6 and D.
Absorption is further hindered by excess ethanol, salt, coffee and phosphoric acid in soda, and things like sweating, stress, lack of sleep, excessive menstruation, certain drugs (especially diuretics and proton-pump inhibitors), insulin resistance and intense exercise can deplete your body of magnesium.36,37
Research shows just six to 12 weeks of strenuous physical activity can result in magnesium deficiency,38 likely due to increased magnesium demand in your skeletal muscle.
For all of these reasons, most people probably need to take supplemental magnesium. The RDA for magnesium is around 310 to 420 mg per day depending on your age and sex,39 but many experts believe you may need a minimum of 600 mg per day.40
I suspect many may benefit from amounts as high as 1 to 2 grams (1,000 to 2,000 mg) of elemental magnesium per day, as the extra magnesium may also help mitigate unavoidable exposures to electromagnetic fields (thanks to its calcium channel blocking effect). To learn more about this, see my previous article on how to reduce EMF exposure.
You can easily improve your magnesium status with an oral magnesium supplement. My personal preference is magnesium threonate, as it appears to be the most efficient at penetrating cell membranes, including your mitochondria and blood-brain barrier. You can learn more about this in "Cognitive Benefits of Magnesium L-Threonate."
Magnesium Testing Is a Valuable Health Screen
Considering the importance of magnesium for good health — including cognition and heart health — it's a good idea to measure your level. GrassrootsHealth Nutrient Research Institute, which has spearheaded research into vitamin D and omega-3, now also offers low-cost testing for magnesium.