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Which magnesium supplement is best?

Magnesium is required for more than 300 different enzymatic reactions in the human body.  Without magnesium you’re not going anywhere; literally.

Despite being present in many fresh foods, studies suggest the majority of the population simply do not consume enough magnesium.  That deficiency, in turn, underpins many chronic illnesses.  Everything from asthma, diabetes, arrthymia, PMS, osteopenia and depression can often be attributed, at least in part, to low levels of magnesium. 

No wonder then that there is such a bewildering bevvy of suppliers of magnesium spruiking their wares on your chemist’s shelves.

But which magnesium is best? Is there actually any difference between them?

First up it’s important to understand that, brand names aside, magnesium is magnesium. It’s an element, like calcium, hydrogen or sodium.  What changes is the compound – what the magnesium is chemically bound to – and that affects how easily it is absorbed in your intestine or skin (bioavailability) and how it affects digestion. 

We looked at six different  suppliers of magnesium and benchmarked all of the ingredients.

Generally magnesium citrate or chelate are the best absorbed forms when taken orally.

Blackmores Super Magnesium and Swisse Ultiboost stand out with 291mg and 927mg of Citrate respectively. Thompsons Organic Magnesium has 806mg of chelate and 100mg of magnesium aspartate which has been used to treat chronic fatigue.

If you’re wondering why there are such large variations between the amounts in each, it’s because they’re measuring the magnesium compound (magnesium citrate, magnesium oxide) and the weight will vary depending on what the magnesium is bound to. 

Look at the bottom of the label and you’ll usually find “Total elemental magnesium” which shows you the actual magnesium content.  

Wagners Super Bio Magnesium has the largest overall amount of magnesium, at 500mg. But 440mg of that is in the form of magnesium oxide which is not terribly well absorbed. It does contain 60mg of magnesium phosphate which has higher bioavailability, but it really underscores the need to read the labels to understand what you’re buying.

Bioavailability (the amount of magnesium your body will absorb) data is difficult to measure because the body will generally absorb more magnesium if it is already low, guzzling it down like a thirsty runner when they’re handed a bottle of water.

Look for chelate, citrate, aspartate or even magnesium l-threonate if you can get it. Magnesium oxide is cheaper to manufacture so that’s why you’ll see a lot of brands using that particular compound.  It can cause stomach upsets in some people but the flipside is if you suffer from constipation, heartburn or indigestion this form can help alleviate some of those symptoms. Just don’t expect a lot of increase in your overall magnesium levels.

Ultimately aim for a brand that gives you good bioavailability (magnesium citrate or chelate) for a sensible price.

 Blackmores Bio MagnesiumBlackmores Super Magnesium +Cenovis MagnesiumSwisse Ultiboost MagnesiumNature’s Own MagnesiumThompsons Organic MagnesiumWagner Super Bio Magnesium
Magnesium Oxide440mg423mg295mg   440mg
Magnesium Phosphate175mg175mg    60mg
Magnesium Chelate 75mg30mg 100mg806mg 
Magnesium Citrate 291mg 927mg   
Magnesium Aspartate Dihydrate     100mg 
Magnesium Orotate     100mg 
                                 Chromium 50mcg     
Calcium Ascorbate50mg        
B650mg50mg60mg   41mg
D32.5mcg2.5mcg   2.5mcg2.5mcg
Manganese4mg4mg6mg   4mg
Vitamin C 50mg    50mg
Total Magnesium300mg305mg 150mg100mg174mg500mg

Magnesium from food

Could you just skip the whole pill thing and get enough magnesium from food? Absolutely, if you’re eating the right things; the usual suspects, green leafy vegetables and nuts, along with brown rice are good sources.

The Australian National Health and Medical Research Council recommends magnesium intake of 410mg – 420mg for men and 310 – 320mg for women (slightly higher if pregnant or lactating).

If you’re aiming for a high magnesium diet, 80mg of magnesium can be found in fifteen cashews or almonds, half a cup of boiled spinach, two cups of cubed avocado, a cup of cooked brown rice or a large steak. Or you could justify pigging out on eight squares of dark chocolate to get that 80mg (but look for one with 85% cocoa or higher to minimise the sugar hit).

Cooking and boiling food scan significantly reduce the amount of magnesium.  Some fertilisers also reduce the amount of magnesium taken up by plants.  Herbicides and pesticides can also kill off worms and bacteria which normally help plants to better absorb minerals – so eat organic where practical.

Coffee and alcohol increase the excretion of magnesium as do some medicines including antacids, antibiotics, antihistamines, and some blood pressure drugs.

Still, even on that perfect day where you eat a lot of healthy food, no coffee or booze, you can see how it can be difficult to get sufficient magnesium into your body. Do you really want to be shoveling down three cups of cooked spinach when a tablet could do?

Do be mindful that calcium and magnesium compete within the body for absorption and should be taken a few hours apart from each other to maximise absorption.