Half of you reading this probably take a dietary supplement—a recent study found that more than 50 percent of Americans (and more than two-thirds of seniors) do. Although multivitamins are falling out of favor (possibly a consequence of research suggesting they’re ineffective at preventing disease), the popularity of certain nutrients has skyrocketed: Between 1999 and 2012, use of vitamin D almost quadrupled, and use of fish oil supplements increased ninefold.

If you’re one of the millions of supplement fans, I want to make sure you’re taking them in a healthy way. Here’s a cheat sheet.

take it with vitamin D. You won’t be able to properly absorb calcium without vitamin D, so try to also get about 600 IUs of D a day.
DON'T overdo it. Extreme amounts of calcium won’t build bionic bones, but may lead to kidney stones or constipation and, according to some analyses, even a higher risk of heart disease. FYI: The recommended daily allowance for most adults is 1,000 milligrams from supplements and food combined; just an eight-ounce container of low-fat yogurt provides 42 percent of that.

Fish oil or omega-3 fatty acids
take them with a meal. This will help minimize unpleasant side effects like burping and heartburn.
DON'T take them with aspirin or other blood thinners (unless they’represcribed by a doctor). These supplements further thin your blood, increasing the risk of bleeding.

take it with a glass of orange juice. Research shows that vitamin C improves your body’s iron absorption.
DON'T wash it down with dairy or antacids. They may contain calcium, which can interfere with iron intake.

Vitamins A, D, E and K
use them as a reason to enjoy some healthy fats. These nutrients may be best absorbed with meals containing fat.
DON'T start taking vitamin K if you’re on an anticoagulant like warfarin. The vitamin could counteract the medicine and make your blood more likely to clot.

make sure you’re also getting enough magnesium in your diet. Magnesium helps regulate potassium in your body. Try nuts, legumes, and dark leafy greens.
DON'T take it with certain blood pressure meds. Using potassium supplements while on ACE inhibitors or angiotensin receptor blockers (like losartan, valsartan, and others that end in tan) can put you at risk for a dangerous amount of potassium in your bloodstream. Hyperkalemia—too much potassium—can lead to muscle weakness, paralysis, and abnormal heartbeats known as arrhythmias.

Medicinal herbs (e.g., ginkgo, ginseng, or St. John’s wort)
take only the amount recommended by your medicalprovider. Even plants can be harmful in high quantities.
DON'T mix with other meds. These supplements may interfere with some prescription drugs (like SSRIs, statins, and warfarin), putting you too far below or above the target therapeutic blood concentrations.

give them something to eat. Probiotics are beneficial microorganisms; prebiotics are carbohydrates that our bodies can’t digest and that help feed probiotics. Prebiotic sources include asparagus, bananas, and legumes.
DON'T assume they’re all the same. The most thoroughly researched are Lactobacillus, Bifidobacterium, and Saccharomyces boulardii. Consult with your doctor about the optimum kind and amount for your personal health.

If You're Taking Any Supplements At All
The FDA doesn't evaluate these products for safety before they go on sale, so look for brands with a mark saying they've been verified by a third party like ConsumerLab.com, UL, NSF International or U.S. Pharmacopeial Convention (USP).

Mehmet Oz, MD, is the host of The Dr. Oz Show (weekdays; check local listings).

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