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Surprising Side Effects of Taking Magnesium Supplements, Say Dietitians

Exactly what goes on in your body when you take this muscle-relaxing mineral.
FACT CHECKED BY Olivia Tarantino

Since it can be tricky to stick to a perfectly balanced diet at all times, it's not uncommon for people (particularly as they age) to take certain supplements in an effort to ensure their bodies are getting the nutrients they need. And while supplements can help rectify some concerning nutrient deficiencies, they can also lead to some problems of their own.

Magnesium is a particularly tricky nutrient because it is involved in a variety of bodily functions. It can also be dangerous if you have either too little or too much magnesium in your system, so finding that perfect balance is key.

"Magnesium is a rarely considered mineral that plays many roles in the body—over 600 functions at the cellular level. While it is a small nutrient, a deficiency has significant implications," says Trista Best, RD, a registered dietitian at Balance One Supplements.

Keep reading for some surprising side effects caused by magnesium supplements, according to dietitians, and for more on how to eat healthy, don't miss 7 Healthiest Foods to Eat Right Now.

1

They can cause nausea, abdominal cramping, and loose bowel movements.

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As an electrolyte, magnesium interacts with sodium levels in the body, which can cause some dramatic results. For example, "magnesium supplementation can stimulate the osmotic activity of unabsorbed salt in the small intestine and colon and also increase gastric motility," says Mary Wirtz, RD, a registered dietitian, and consultant for Mom Loves Best. Gastric motility is the movement of food from the mouth all the way through your intestines, thus supplementing with magnesium can speed up digestion to the point that you may experience loose bowel movements.

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2

But they can also make you regular.

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"On top of a well-rounded diet, magnesium supplementation can offer many benefits. If you struggle with constipation, magnesium may improve bowel regularity along with ample hydration," shares Skylar Griggs MS, RD, LDN, a registered dietitian and nutrition expert in the Boston area. "Specifically, magnesium citrate allows for the increase of water in the digestive tract and relaxation of the bowel muscles."

3

They can improve your sleep quality and quantity.

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"Along with fighting depression and lowering blood pressure, magnesium is linked to better sleep in both quality and quantity," Best explains. "It does this by regulating and activating parasympathetic hormones and neurotransmitters that help the brain to enter a state of relaxation which is better prepared for rest. Magnesium also helps to control the symptoms of some conditions that interrupt sleep, like digestive disorders." She adds: "Magnesium deficiencies almost always lead to or exacerbate insomnia."

4

They can lead to magnesium toxicity.

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According to Wirtz, taking magnesium supplements can also cause magnesium toxicity, which in turn can "result in various side effects such as low blood pressure, vomiting, retention of urine, depression, and muscle weaknesses."

However, Wirtz clarifies that this particular side effect is unusual and "generally associated with extreme amounts of supplementation and/or underlying impaired kidney function."

5

They can help maintain a healthy blood pressure.

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"Magnesium is a mineral that plays an essential role in maintaining proper blood pressure and keeping our bones strong," Griggs explains. "Some of the richest sources of dietary magnesium include dark leafy greens, salmon, nuts, and seeds."

Related: The #1 Best Diet to Lower Your Blood Pressure, Says Dietitian

6

They can interfere with specific medications.

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If you're taking medications, especially antibiotics, Wirtz warns that you might want to steer clear of magnesium supplements, because they can interfere with the medicine. "It's always important to discuss any specific nutrition supplements with your primary care provider," she says.

Per a 2019 study, magnesium can have a negative impact on the absorption of some drugs, thus making them less effective. To err on the safe side, you can always supplement your diet through food sources of magnesium: 28 Best Foods to Eat for Magnesium.