What Does Magnesium Do For the Body?

When it comes to nutrition, if something sounds too good to be true, it probably is. Meal replacements may claim to strike a perfect balance of nutrients, but they taste terrible. Supplements like probiotics and vitamin B are touted as cure-alls for a wide range of ailments, but they’re largely unregulated and most people don’t need them. Now magnesium is getting the silver-bullet treatment. Marketers of magnesium pills, body sprays, and bath salts claim that their products will boost recovery and energy levels and promote all kinds of important-sounding bodily functions like DNA synthesis and bone strength. Here’s what you need to know about getting enough magnesium.

Magnesium Is Not a Health Food, It’s an Essential Nutrient

Unlike trendy (and expensive) health foods like acai and ashwagandha, magnesium is an essential nutrient that’s naturally found in many of the foods you’re already eating. If you remember anything from high school chemistry, you might know that magnesium is technically a metallic element. In nutrition, it’s classified as a mineral and falls into the micronutrient category, which includes vitamins and minerals that your body depends on to function. Your body can’t produce magnesium, though, so you need to get it from your diet. Adults require 300 to 400 milligrams of magnesium per day, which is doable if you’re regularly eating good sources like nuts, seeds, legumes, whole grains, leafy greens, certain fruits and vegetables, and fatty fish.

Without It, You’d Be Dead

Magnesium is abundant in the body. Hundreds of biological processes, including the creation of new proteins, energy production in cells, and DNA synthesis, depend on it, explains Colin MacDiarmid, a senior nutrition scientist at the University of Wisconsin–Madison. Without it, the body stops working. Because it’s so important, your body is good at holding on to the magnesium you ingest, most of which gets stored in your bones, where your body can access it as needed. If your bones get too low on magnesium because you’re using it up without properly replenishing it through your diet, they can weaken over time.

It Might Be Hard to Tell if You’re Magnesium Deficient

A 2018 review published in Open Heart estimated that anywhere from 10 to 30 percent of people in developed countries have a mild magnesium deficiency, which might come with few or no symptoms. “Many reports argue that subclinical deficiencies are widespread and poorly recognized and may contribute to the development of many different chronic diseases, including cardiovascular disease, mood disorders, and hypertension,” MacDiarmid says.

Severe deficiencies, while uncommon, are easier to spot. Symptoms include loss of appetite, vomiting, and fatigue, which might be followed by numbness, muscle cramps, seizures, personality changes, and coronary spasms as the deficiency continues, according to the National Institutes of Health. Your doctor can measure magnesium levels in your body with a blood test.

Keep Calm and Eat Whole Foods (Plus a Supplement, Maybe)

A doctor might prescribe magnesium supplementation if you regularly experience cramps, fatigue, or irritability. And in some cases, magnesium might be used to treat constipation, says Aja McCutchen, an Atlanta-based gastroenterologist. But a healthy diet rich in whole, unprocessed foods is still the easiest protection against a magnesium deficiency. (Processing grains and other foods reduces their magnesium content, notes MacDiarmid.) An ounce of raw almonds—about a handful—contains 80 milligrams of magnesium.

If you don’t regularly load up on magnesium-rich foods, or if you experience the mild symptoms (cramps, fatigue, and irritability) mentioned above, supplementation might be a good idea. There’s no benefit to supplementing unless you’re deficient, says MacDiarmid, but there isn’t much risk either. While some vitamins and minerals are extremely toxic in high doses, magnesium is relatively nontoxic because we have effective mechanisms to prevent excess magnesium absorption. The exceptions are people with kidney problems, who might not be able to properly excrete excess magnesium, and people on certain drugs—so check with your doctor before adding a magnesium (or any) supplement.

There’s No Need to Get Fancy

If you’re browsing supplements and don’t know whether to spring for the expensive stuff or take a chance on a budget-friendly brand, don’t stress. “It doesn’t really matter which one you take,” MacDiarmid says. “It’s not clear that any form of magnesium is more easily absorbed or more effective.” Supplemental magnesium usually exists as magnesium oxide, magnesium aspartate, or magnesium citrate (which provide magnesium bound to different compounds, like oxygen, aspartic acid, or citric acid, respectively), but it all breaks down to the same molecule in your body. Your body might tolerate some forms better than others, so if you experience discomfort after starting a supplement, it’s worth trying out another.

And while products like magnesium-enriched oils, creams, and bath salts have been gaining traction, science says slathering it on your body probably won’t do much. A 2017 review of studies that examined the effect of topical applications of magnesium (including soaking in the Dead Sea) found that the vast majority didn’t produce statistically significant increases in the subjects’ magnesium levels. More research needs to be done, but for now, skip the expensive oil.

The bottom line: it’s possible that you have a slight magnesium deficiency, but anything short of a blood test can’t prove it. If you’re concerned, talk to your doctor about taking an inexpensive magnesium supplement.