Too much of a good thing

August 11, 2003

The first time I heard Dr. Wright refer to magnesium-induced nutrient deficiency, I was sure I’d missed a step in the conversation: There’s just no way a nutrient — especially one as beneficial and important to our health as magnesium — could cause other vitamin and mineral deficiencies. Or so I thought. Dr. Wright filled me in on the whole magnesium story, and it’s information you need to know too.

Don’t get me wrong. Magnesium is an essential nutrient with hundreds of known functions in the body. From maintaining and improving energy levels, to building bone density, to treating migraines — there are many reasons why you should supplement with it. But even if your only supplementary magnesium is from a multi-vitamin, it’s possible you’re getting “too much of a good thing.”

In the late 1970s, Dr. Wright worked with a professor from a major university whose knowledge and use of vitamins and minerals was well ahead of the university’s medical school. In his first meeting with Dr. Wright, the professor explained that he’d been been following an excellent diet and taking a comprehensive list of vitamin and mineral supplements for several years, but he still felt “all tired out.”

So the two doctors did some tests. Surprisingly, nearly all his mineral levels were low — even compared to individuals who had not been supplementing with minerals at all. Some of his other nutrient levels were also lower than expected. After several negative tests for more common causes of nutrient malabsorption (low stomach acid, insufficient digestive enzymes, allergy), they discovered that his 500 milligrams-a-day dose of magnesium was the culprit.

It turns out that the magnesium was causing something called “gastrointestinal hurry.” If you’ve ever taken milk of magnesia, you know that large quantities of magnesium can irritate the bowel and will usually make you “go.” But magnesium doesn’t always cause noticeable symptoms: It may speed up the process without causing diarrhea or loose stools.

Although estimates vary, a reasonable range for normal intestinal transit time (the length of time food takes to go from the entrance to the exit of the gastrointestinal tract) varies from 12-14 hours to 20-24 hours. You can measure your own transit time easily by eating beets or corn or swallowing charcoal tablets and observing how long it takes to emerge.

Dr. Wright’s colleague found that his transit time was approximately 18 hours without his usual 500 milligrams-a-day dose of magnesium. With the magnesium, his transit time dropped to 9 or 10 hours. Because the nutrients he was eating and supplementing with were expelled so quickly, his body didn’t have time to absorb them. He had a classic case of magnesium-induced nutrient deficiency brought on by intestinal hurry. He later found that the largest amount of magnesium he could take each day without causing this “hurry” was 250 milligrams.

One last thing…

Most people can take more magnesium each day without risking gastrointestinal hurry or magnesium-induced nutrient deficiency. Dr. Wright finds that 200 mg to 600 mg is sufficient for most of his patients. But keep in mind that magnesium-induced nutrient deficiency can happen even at lower doses.

If you’re feeling a bit tired, and can’t blame it on lack of sleep, why not check yourself for this problem? It’s certainly one that’s easy to test and easy to fix!

Yours in good health, Amanda Ross Managing Editor Nutrition & Healing

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