Can food and dietary supplements affect my medication?

Dariush Mozaffarian, MD
Internal Medicine
It's true that certain nutrients in food and supplements can interfere with the medications you take. Prime examples are calcium and iron, which bind to the antibiotic tetracycline so that both the nutrients and the drug simply pass through the body in an unusable form. Megadoses of vitamin C can acidify your urine, which curbs the excretion of acidic drugs, such as aspirin. That means the aspirin will stay in your body longer than usual.

Generally, when you begin using a medication, your pharmacist will warn you about any foods to avoid. But you should never take a dietary supplement without finding out whether it might interfere or interact with the prescription medications you take. Ask your pharmacist or doctor -- not the clerk at a health-food store -- for this information. It helps to buy all your prescription drugs and supplements at one pharmacy, especially if the store maintains computerized customer records to track possible drug interactions.
Shereen Jegtvig
Nutrition & Dietetics
Dietary supplements and foods can interact with medication. Vitamin E, for example can interact with blood thinners and grapefruit juice interacts with several medications. Your pharmacist can provide you with a list of supplements or foods that may cause problems. Always speak to your doctor before you take any types of dietary supplements.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.