What Is Magnesium? | Health Benefits, Side Effects & Supplement Dosage |PART 1

By Myprotein Writer | Chris Tack

Clinical Specialist Physiotherapist 

Magnesium (Mg) is usually an abundant and always an important mineral in our bodies. It is required for more than 300 reactions in the body, involving metabolism, protein synthesis, cellular energy production, cell growth and DNA/ RNA development(1-2).

In this two part article series we will examine how magnesium can benefit not only our health, but also our sporting performance.


What does magnesium do?

Magnesium has a variety of functions which include maintain of the health of the body’s tissues (including nerve, muscle and bone); management of heart function (including the rhythm of our heart beat); our muscle tone; our blood pressure; our immune system; and our blood glucose levels (1-2).

What Is Magnesium? | Health Benefits, Side Effects & Supplement Dosage

However, these functions can only be sustained for as long as we sustain an appropriate concentration of Mg in our tissues. When we are unable to sustain this level is when issues occur.

Magnesium has been described as an “invisible deficiency”- predominantly because only a small percentage of magnesium is stored in our blood; and in order to know if you are deficient a blood test is taken. Therefore a blood test may come back as negative, and you may still have a deficiency of magnesium in either your muscles or your bones where it is more readily stored. Deficiency of Mg is actually not uncommon and therefore should not be ignored.


The Invisible Deficiency


Most magnesium intake deficits are marginal to moderate (e.g. 50%-90% recommended daily allowance is consumed)(3).

However, the spread of Mg deficiency is relatively wide. For example, deficiency has been observed in the young(4-5) and has links with the aging process(6). It has been seen in females more than males(4,7) but also has been identified in young men(8).

Deficiency has also been seen in varied sporting groups, including runners(9); ultra-endurance, adventure racers(10); and gymnasts(11). It has even been seen in varied team sports such as both football(12) and rugby(13).

Reasons for the wide spread of Magnesium deficiency

1) Modern food processing methods remove magnesium from our foods (e.g. refining grains)(14). Process foods such as vegetable oil, sugar, white flour and most things out of a box will be devoid of magnesium. Even industrial farming techniques will reduce the soil from which our food is grown of its magnesium.

2) Cooking processes (especially boiling) can remove magnesium.

3) Magnesium is not a compulsory requirement of our food labels for nutritional labelling.

4) Water treatment to soften water removes magnesium, meaning we do not sufficiently drink enough. Even bottled waters will be low on magnesium.

5) Other substances we consume can have effects to prevent magnesium absorption (e.g. phosphoric acid in carbonated soda will bind with Mg and prevent intestinal absorption) and calcium supplementation will block Mg absorption).

6) We lose too much of our bodies Mg through excretion in urine (particularly if you each too much sugar or salt, or drink too much tea/ coffee/ alcohol, or exercise intensely, or are stressed…)


Sources of Magnesium?


According to the US department of agriculture some specific foods have high amounts of magnesium, which include 1 ounce of almonds (80mg/ 20% of the dietary reference value) and half a cup of spinach (79mg/ 20% of DRV)(14).

Other sources could include peanut butter (49mg in 2 tablespoons), whole wheat bread (46mg in 2 slices), baked potato (43mg in 3.5 ounces), and brown rice (42mg in ½ cup).

Alternatively there are a variety of forms of supplementation, which include magnesium oxide, citrate, chloride, aspartate, lactate or sulphate(15-16). The important thing to consider when choosing is that aspartate, citrate, lactate and chloride are more readily absorbed and more “bioavailable” than both oxide and sulphate(18-22).

Additionally forms which can be dissolved in water are more easily and completely absorbed which increases the supplement’s efficiency(16-18).

nut butter

Magnesium | Health Benefits

#1 Aging and Magnesium

What Is Magnesium? | Health Benefits, Side Effects & Supplement Dosage

The process of aging is often associated with Mg deficits. Usually during the process of getting older whilst plasma (blood) concentrations of Mg are sustained, the total amount of Mg in the body is reduced(25). Alternately, as we age secondary causes may reduce magnesium in the body (e.g. gastrointestinal issues may prevent absorption or there may be greater loss of Mg in urine).

However, we also know that oxygen-derived free radicals are produced at a greater rate in the elderly(25) and subsequently cause chronic inflammation states in the bodies tissues. From this state of increased and prolonged inflammation a variety of diseases can emerge.

#2 Bone Density and Magnesium

A further physiological influence Mg has in the body which we shall discuss is its effect on bone formation.

Magnesium has an effect in modifying the activity of two different types of cells: osteoblasts (which assists bone formation) and osteoclasts (which assist bone absorption)(43). They also alter the concentration of other substances which influence bone formation- namely parathyroid hormones and vitamin D.

What Is Magnesium? | Health Benefits, Side Effects & Supplement Dosage

A reduction in Mg, therefore can lead to an imbalance between bone formation and bone loss. Positive relationships have been seen between the amount of Mg consumed and bone density in both men and women(44).

In those who suffer bone density diseases (such as osteoporosis), a reduced concentration of serum magnesium levels have been found compared to individuals with normal bone density(45). Thus supporting the fact that Mg deficiency is a potential risk factor for osteoporosis.

Consequently studies have examined the effectiveness of increasing Mg intake in these populations; and indicate that this may assist bone mineral density maintenance and increase in post menopausal and elderly women(46). Dosages of 290mg per day of Mg citrate for a period of 30 days has shown reduction in rate of bone turnover compared to placebo (suggesting a decrease in bone loss)(47).

Furthermore, a study in elite swimmers (a group where bone density issues have been seen due to the reduced amount of impact and loading through the skeleton) has shown both a reduction in bone density and Mg deficiency to the extent where Mg intake was described as an independent predictor of the degree of bone mineral density loss(48).

#3 Physical Performance and Magnesium

A further point to be made is to highlight the effect of Mg supplementation (in those with Mg deficit) on age-related physical performance decline. It has been shown that a 12 week course of 300mg per day of Mg oxide was sufficient to improve the muscular and physical performance of the hands and legs of a group of ladies of approximately 70 years of age(50).

The importance of this can not be understated, as it indicates that even if age or disease related health has been prolonged over a large number of years, Mg supplementation can be of benefit to help assist people to be more active and healthy.

Magnesium | Dosage

The recommended daily allowance for magnesium ranges from 400-420mg per day in males, and 310-320mg per day in females(46).

The tolerable intake levels for supplementary magnesium are different and in children this would reduce to 65mg between ages 1-3, 110mg for ages 4-8, 350mg for ages 9-18, and 350mg for 19 years +(46).


Magnesium | Side Effects


Toxicity of magnesium is generally prevented in healthy individuals as the kidneys eliminate excess Mg in urine (50); however dosages beyond 5000mg per day have been associated with mortality in both children (51) and older adults (52).

Normal side effects from high dose consumption

? Diarrhea, nausea and abdominal cramping.

This is particularly evident with high doses of magnesium carbonate, chloride, oxide and gluconate (18). The laxative effect of excessive consumption is due to magnesium salts being unabsorbed in the intestine and colon, which modifies movement of fluids and stimulates gastric motility.

Symptoms of potential toxicity

? These include hypotension, nausea, vomiting, facial flushing, urinary retention (not being able to fully empty your bladder), lethargy and muscle weakness, breathing difficulties and cardiac arrest(50).

Caution should be taken with supplementation in the presence of impaired renal function due to the inability to remove excess magnesium (50).

Taking other medications?

Another consideration is the impact of magnesium supplementation when taking other medications. For example, magnesium supplementation should be separated from the use of oral biphosphonates (used to treat osteoporosis) by 2 hours to prevent dampening the effect of the medication (53).

Additionally anti-biotic medications from the tetracycline family (e.g. doxycycline) should be taken either 2 hours prior to, or 6 hours following a magnesium supplement (54). Medications such as potassium-sparing diuretics (e.g. spironolactone) will reduce frequency of urination and reduce excretion of magnesium- therefore caution should be taken to avoid toxicity.


Take Home Message


And so concludes the first part of our magnesium saga… So far we have learnt that deficiency in magnesium concentration is common, and that having a deficiency can lead to a number of age related disease states characterised by increased oxidative free radical activity, glucose metabolism changes and bone formation imbalance.

Alternatively, we have also seen the apparent benefits of supplementation to counteract the risk of disease and prevent deficiency.

In part 2 of this piece we will explore the ergogenic benefit of magnesium supplementation, and whether it can not only sustain health as we age- but also whether it can improve athletic performance!

Many thanks,


What Is Magnesium? | Health Benefits, Side Effects & Supplement Dosage


Our articles should be used for informational and educational purposes only and are not intended to be taken as medical advice. If you’re concerned, consult a health professional before taking dietary supplements or introducing any major changes to your diet.

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Casey Walker

Casey Walker

Experienced Sports Nutrition Technologist

Casey Walker is an experienced sports nutrition new product development technologist. He holds a Bachelor of Science in Sports and Exercise Science and a Master of Science in Sports Sciences and Physiology. Casey’s scientific research area of expertise lies in the effects of dietary nitrates on sprint performance and exercise-induced muscle damage. He has also worked as a sports scientist for a medal-winning Paralympic track cyclist, with a goal of qualifying for the Rio 2016 Paralympics. Find out more about Casey’s experience here: In his spare time, Casey is a keen middle-distance runner with an interest in triathlon. He’s always looking out for the latest blends and supplements to improve his half-marathon time and recovery.