The Reason Why Your Vitamin D Supplements Aren’t Working

Without this mineral, your vitamin D supplements may not work properly—leaving you at risk for all kinds of trouble.

Receiving vitamins. Concept illness, colds, cure, fall and winterOlha Tsiplyar/Shutterstock

Even if you eat a decent diet, you could be falling short on magnesium. You need the mineral to keep your heart healthy and your energy high—and new research suggests you may also need magnesium to keep vitamin D from harming your health. The findings come from a scientific report recently published in the Journal of the American Osteopathic Association.

Vitamin D is crucial for bone growth, controlling blood sugar, and it may even protect against some types of cancer. In a collaborative effort between Harvard University and the University of Rwanda, researchers have discovered that without enough magnesium, those D supplements aren’t only worthless but they could be dangerously increasing your levels of calcium and phosphate. After analyzing how vitamin D behaves in the body, the researchers discovered that magnesium helps activate the vitamin so that the body can put it to use. Watch for the signs you’re not getting enough vitamin D.

For women, the daily recommended allowance for magnesium is between 320 and 360 mg; for men, it’s between 410 and 420 mg. The authors note that magnesium is naturally present in “almonds, bananas, beans, broccoli, brown rice, cashews, egg yolk, fish oil, flaxseed, green vegetables, milk, mushrooms, other nuts, oatmeal, pumpkin seeds, sesame seeds, soybeans, sunflower seeds, sweet corn, tofu, and whole grains.” In addition, some foods are fortified with the mineral. Despite all the potential sources, the average American only gets about 50 percent of the RDA; nearly half are at risk of being dangerously deficient. Here’s how to tell if you have a magnesium deficiency.

“Studies have shown that magnesium supplementation can increase the effectiveness of vitamin D activity,” the study authors write. “Therefore, further controlled studies should determine the dose…required for reducing vitamin D-associated disorders.” In the meantime, look to get more magnesium-rich foods in your diet and, if you’re downing a D supplement, consider adding a magnesium pill to your regimen.

Next, find out which vitamins are a total waste of money.

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Lauren Cahn
Lauren Cahn is a New York-based writer whose work has appeared regularly on Reader's Digest, The Huffington Post, and a variety of other publications since 2008. She covers health, fitness, yoga, and lifestyle, among other topics. An author of crime fiction, Lauren's book The Trust Game, was short-listed for the 2017 CLUE Award for emerging talent in the genre of suspense fiction.