10 Dietary Supplements Runners Should Avoid

What?! Not take antioxidants?! That's right: You shouldn’t, true story. For years runners popped these two popular vitamins (often together) because they believed vitamins C and E could help fight off the cell-damaging free radicals you produce during exercise. Well, they can—and that’s the problem.

Related: Nutrition & Weight Loss

Scientists now know that a little free-radical production is a natural and necessary part of training adaptation. Your body creates its own natural antioxidants to quell free radicals after hard training bouts. As you continue to train, your body actually gets better at this—if you don’t get in its way by feeding it extra antioxidants. Taking high doses of these free-radical fighters may actual impede endurance performance because it impedes these adaptations, says Stanford-based exercise nutritionist and physiologist Stacy Sims, PhD. What’s more, a review of 11 studies on vitamin C and vitamin E has recommended against taking high doses of antioxidant supplements because the evidence doesn’t support their benefits. Vitamin E supplementation has also been linked to small increases in cancer and death and, well, neither of those is any good.

Get these essential nutrients from your diet instead. Fruits and vegetables are brimming with vitamin C, so it’s easy to get the 75 (for women) to 90 (for men) milligrams you need a day. A half-cup of sweet red pepper, which delivers more than 140mg by itself, will get you there. Getting the recommended 15mg of vitamin E is trickier, but far from impossible. Good sources include nuts, dark leafy greens, avocados, and shellfish. An ounce of almonds (about 24 nuts) and a cup of spinach will just about meet your needs.

True story: Two large studies on more than 47,000 smokers taking beta-carotene—a precursor to vitamin A—actually had to be halted because the folks taking these antioxidants were getting cancer, as well as heart disease, at higher rates than those taking dummy pills. The researchers discovered that though foods rich in beta-carotene seemed protective for smokers, one whopping dose of the antioxidant seemed to fortify the free radicals and cause great harm. Worse, a study on the same participants found that they were still at a higher risk for cancer and death a full decade after they’d stopped taking the supplements. Get the 700 (women) to 900 (men) micrograms of vitamin A you need through foods like bright orange fruits and veggies. Just one sweet potato packs 960 micrograms of beta carotene, which is converted to vitamin A in your body.

Health - Injuries has been making headlines in recent years, and with good reason. Studies show that vitamin D deficiency is common in athletes, and up to a quarter of the population has low blood D levels. That’s bad: vitamin D is essential for building and maintaining strong bones and for optimal muscle function and recovery.

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While the 400 International Units (I.U.) you need is best gotten from the sun and natural food sources, such as fortified dairy and fatty fish, it’s okay to take supplements of vitamin D, especially if you limit sun exposure and don’t regularly include those foods in your diet. It’s important to be mindful of the form you take, however. A 2013 study published in the journal Nutrients reported that athletes taking high levels of vitamin D₂ (a plant version of the nutrient) actually experienced more muscle damage following a hard gym session than those who took dummy pills.

If you’re going to supplement, take vitamin D₃, the form that your body creates when sun hits your skin. “You can also get some vitamin D from foods like fish, mushrooms, and fortified foods like milk and yogurt,” says Elliott.

Surprised? Taking calcium to protect your bones is advice as old as your bones themselves. Turns out, it may not be such good advice.

In 2013, the All About 75 Hard recommended that postmenopausal women refrain from taking calcium, after reviewing more than 135 studies that concluded that calcium supplements didn’t prevent fractures. Worse, there’s growing evidence that calcium supplements may increase risk of heart disease and stroke. In one landmark study of 400,000 men and women, men taking more than 1000mg of the mineral were 20-percent more likely to succumb to heart disease than men who didn’t take the supplements. Researchers believe that the mineral may be being absorbed in the artery walls instead of the bones.

You can easily get the 1000mg to 1200mg recommended daily amount through dairy foods like Nutrition - Weight Loss, as well as fatty fish, especially canned salmon.

Unless you’re pregnant (in which case, work with your doctor), dosing up on this B-vitamin—which may help prevent neural tube birth defects, anemia and heart disease—can backfire on your health. Recent research shows that high doses of folic acid actually lower immune function and appear to increase your risk for cancer. Folic acid is abundant in our food supply, so it’s easy enough to get the 400 micrograms you need every day. Foods to get: fruits; leafy green vegetables (especially spinach); nuts; beans; peas; dairy products; grains; fortified grain products like cereal; meat; poultry; eggs; and seafood.

This one is a long time favorite amino acid supplement among sprinters because it helps build muscles by pulling water into your muscle cells and increasing protein synthesis. But though it’s well tested and has been found to be safe, it taxes your kidneys and—because it pulls water into your muscles—has been suspected to contribute to dehydration, heat-related illness, and muscle cramps. It’s another one far better to get from natural sources like meat (especially beef) and fish like herring.

Runners need plenty of magnesium, an electrolyte mineral that plays a starring role in blood-sugar control and muscle contractions, and is involved in more than 300 biochemical reactions in your body. Studies show that only about a quarter of US adults get the 320mg (women) to 420mg (men) they need, so a supplement isn’t a bad idea—but you need to take one that your body can absorb, and magnesium oxide is the poorest-absorbed form.

Opt for magnesium glycinate instead. Even better, ramp up your intake of magnesium-rich foods like dark leafy greens, nuts, fatty fish, avocado, bananas, and seeds—just a half cup of pumpkin seeds deliver 100 percent of your daily recommended dose.

B vitamins help convert food into the energy you need to function, let alone exercise—but there’s absolutely no need to take in additional amounts through a pill. B vitamins are ubiquitous in the food supply, found in fruits, vegetables, grains, and fortified cereals and grain products. Taking more than you need is a waste of money and, in some cases—as with B6 and B12—can have adverse health effects. 

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A 19-In 2013, the found that those who took supplements had, on average, a 2.4-percent increased risk of dying over the course of the study than those who didn’t. That’s not a huge percentage, and there’s no proven cause and effect, but new research is always showing how certain vitamins and minerals can be harmful in higher-than-necessary doses: Multivitamins might not be worth the risk, or the money. Also, if you consider that much of our food supply is already fortified, it can be pretty easy to get more vitamins and minerals than you need without knowing it, if you also take a daily supplement.