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Magnesium Recommended Intake and Upper Limit

Question:
How can the Recommended Daily Allowance (RDA) for magnesium be higher than the Upper Tolerable Intake Level (UL)? That is, how can an amount which is healthful also put you at risk for harm?

Answer:
It is true that, at first glance, there seems to be a contradiction. For example, the UL for magnesium (above which the risk of adverse effects increases) is 350 mg per day for adults and children over age 8, but the RDA (the amount one needs) can be as high as 420 mg for many people within this group depending on gender and stage of life.  However, the magnesium one consumes from food does not count toward the UL; only magnesium from supplements and medicine can cause adverse effects and counts toward this limit. So, as long as you're not getting more than 350 mg of magnesium per day from supplements and/or medicine and are getting some magnesium from foods (like whole grains, nuts, beans, and green leafy vegetables) you can satisfy the RDA without exceeding the UL.

For more about this, see the "What to Consider When Using" section of the Magnesium Supplements Review.

The ULs established for niacin and folate also only apply to the amounts consumed from supplements and fortified foods and not from foods naturally containing these vitamins. For vitamin E, the upper limit is higher for the natural form than the synthetic form.

For recommended daily intakes and upper limits for these and other nutrients, based on gender and stage of life, see ConsumerLab.com's Recommended Daily Intakes and Upper Limits page.

Learn more about magnesium:



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I've read that magnesium deficiency is rare but also that most people don't get enough magnesium. How can these both be true? >>

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Comments
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Henry16480   February 21, 2018
I believe the difficulty is resolved by spreading the dose out.
Many people get loose stools if they take > 350 mg of Mg at a time.
That problem can be avoided by taking 2 doses of300 mg Magnesium - about 8 hours apart.
I came to this realization after finding out that horses and cattle get about 5X more Magnesium per day (per body weight) than humans - because their Magnesium is consumed across the entire day - with perhaps only 200 mg in the gut at a time.

ConsumerLab.com   February 21, 2018
Hi Henry - Thank you for your comment; however, this is not recommended and exceeds the upper limit, since magnesium supplementation alone should not be used to meet the RDA.

This CL Answer initially posted on 7/14/2015. Last updated 8/3/2017.

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