In the USA, interest in magnesium (Mg) has risen for the following reasons that are all true:
- A lot of people eat less than the Recommended Dietary Allowances (RDA) amounts
- Certain health problems, prescription drug use, and other conditions can raise Mg needs due to lowered Mg absorption or retention
- Multi-nutrient supplements often omit Mg or add it at a low % of the RDA (because large percents cannot be fit into a small pill)
- Mg affects many body processes that can impact health.
These reasons justify giving attention to Mg, but what, if any, benefits would occur if many USA people would up their Mg intake? As with so many nutrition questions, I wish we had more information. Some data does seem to link optimal Mg intake to health benefits, but exact relationships are not settled. Also, it’s hard to pinpoint optimal intake when it’s difficult to assess people’s Mg functional state. Physicians typically use serum or plasma Mg for this purpose. Real low values usually mean a severe deficiency, but substantial changes in Mg status can occur with small or no changes in serum or plasma Mg. For example, in a study by my team (1), Mg glycinate supplementation caused no change in plasma Mg, but did improve bicep curl exercise performance. Also, red blood cell potassium went up (Mg helps puts potassium into cells).
Some researchers assess Mg state by a combination of measures. This can include how fast a single Mg dose is cleared from the blood and practical assessments (like exercise performance). However, such approaches are hard to implement in a healthcare setting. Despite our current knowledge limitations, here are some thoughts I have now.
To all adults: get at least the RDA from diet + supplements. The adult RDAs are 400-420 mg for men (depending on age) and 310-320 mg for women. These are based on data from old balance studies (measures of what goes in minus what goes out). The well-respected mineral researcher Forrest Nielsen (2) has stated that this data has grown outdated. Newer balance data with improved methodology indicates that the RDAs could be lowered. On the other hand, even as far back as 47 years ago, some mineral researchers have argued against using just balance studies to set mineral RDAs (ie 3). This may especially true for Mg according to some scientists (ie 4). And, even if balance studies are used, Dr. Nielsen points out that this work generally uses “ideal” conditions and people rather than typical states. These ideal states include a fairly low body weight. In all likelihood, Mg needs are proportional to body weight. My attitude is that it doesn’t hurt to get the current RDAs and such intakes may be better than lower intakes.
What about higher intakes? Going up to 500mg/day may have some value, though data supporting that is still limited. You can get this amount from your diet, though it may take some attention to detail. You can see how much Mg you eat in a day using the many online food Mg tables.
Researchers from Israel have written that even going up to 600 mg/day is harmless (4). This may be true if one avoids laxative effects from certain Mg supplements (like Mg citrate). The Israel researchers further write that a moderately high Mg intake might lower risk of cardiovascular disease and help postpone death in general (4). These claims are based mostly on association of serum or plasma or dietary Mg with cardiovascular disease and general mortality rates. However, associations don’t prove cause and effect (ie. high Mg diets may often have some other good aspects). Also, the paper (4) doesn’t actually make a case that an ideal Mg intake has to reach 600 mg/day. The paper’s recommendation of this much just suggests that this amount may ensure most generic people’s needs are covered.
All of this section’s comments assume that other than high body weight, no situation is strongly driving up Mg needs. Multiple situations can do just that. For instance, an Italian research team proposes that intense exercisers need up to 20% more Mg than usual (5). This would push a Mg recommendation of 500 mg up to 600 mg for this type of person. That may hold true, but I can’t say yet that I know for sure that the extra is helpful. A list of other conditions that may raise Mg needs appears on the blog Facebook page (use the link on the top right of this page). If you fit a high risk category, work with a registered dietitian and other health professionals. You should be monitored for Mg status even if just by the imperfect serum Mg. If you have low values, you may need to temporarily take relatively high doses of Mg to get to a normal Mg state.
If you do take a supplement, I recommend Albion Mg glycinate (also called bisglycinate). Look for a label that lists Albion or uses their trademark TRAACS. This form absorbs well and doesn’t have laxative effects like Mg citrate (though one can limit Mg citrate’s laxative effects by not taking too much at once). Mg orotate has been said to deliver Mg to cells especially well, though I have not seen good data for this (and it’s more expensive than most Mg supplements). The orotate itself may have biological actions, but that falls outside a Mg discussion. I don’t recommend Mg oxide. It has some laxative effects and some data suggests it’s not absorbed as well as Mg glycinate. The latter is now being made by companies other than Albion. However, I have yet to see data on the non-Albion versions stability and effectiveness.
If you have had an oxalate kidney stone, take a Mg supplement. Many of the best Mg foods are high in oxalates. Stone formers are often told to restrict oxalate intake. This type of diet makes it hard to meet Mg needs. Besides this concern about meeting Mg needs, Mg chemical properties could inhibit kidney stone formation. Unfortunately, studies on Mg supplement use for kidney stone prevention give mixed results. The inconsistency could be caused by study design flaws, especially in the choice of the Mg form. So, I still recommend Mg supplementation for stone formers. It could help and it won’t hurt.
Is there more to say? Yes, a lot, but it won’t fit in a short article. More will be presented in a book I am writing called The Authoritative Guide to Nutritional Supplements. This will include topics like when to emphasize just diet for getting Mg and when to consider supplements