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Hidden risks: 3 foods and medicines you shouldn't mix

Many Americans are unaware of the risks of mixing meds and certain foods.
/ Source: TODAY

Nearly seven out of 10 Americans take at least one prescription medicine. While much of the focus of medication use is to take as directed, there’s another important topic to address: the hidden risks of mixing some foods and medicines.

Foods that are eaten regularly and are healthy, nutrient-rich choices can be potentially health-damaging when mixed with some medications, including some popular over-the-counter products like pain relievers and antacids.

Foods impact medication activity in the body in three ways, that can either boost or block the effectiveness of the drug:

  • Interferes with the digestion of the medicine
  • Blocks the normal breakdown of the medicine
  • Mimics the action of the medication

Here are three of the most common food and medicine interactions:

1. Grapefruit

This citrus fruit contains a compound that can block the breakdown in the intestines of a number of medications including some (but not all) of the cholesterol-lowering medicines (statins), antidepressants, migraine medications, blood thinners, blood pressure medicines and diabetes drugs.

But it’s not all citrus fruits to limit or avoid. Only pomelos and Seville oranges have a similar action. Other citrus fruits are fine. And watch out for Seville orange marmalade, a popular way this type of orange is consumed. “Limiting” means a six to eight ounce glass of juice or a half grapefruit.

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2. Dark leafy greens/vegetables

Vitamin-K rich foods like these can interfere with the action of some blood thinners. Blood thinners prevent clots from forming, and vitamin K promotes blood clotting, which counters that effect. An important consideration is to keep the amount of these foods limited, but consistent.

Determine with your doctor the total daily number of servings — it might be two cups of salad and one serving of broccoli — and stick with that, to ensure that the dose of the blood thinner selected remains effective. And there are some blood thinners that do not have this effect —so talk to your doctor to see if this might be an option for you.

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3. Dairy products/calcium supplements

Dairy foods can interfere with the absorption of some antibiotics and iron supplements, so avoid taking these together. And while calcium found in dairy products is a health plus, beware of excess dietary calcium supplements when taking some antacids (anti-reflux medicines), which are already rich in calcium. Tally up your total calcium intake from all sources, to not more than 1000 – 1200 mg daily.

And dietary supplements are part of the dietary picture. Many of these can mimic the effects of prescription medications. And the manufacturing of dietary supplements does not have the same federal regulations to meet as do prescription and over the counter products. Concentrated forms of foods in pill form provide much higher doses of active ingredients than the real food, and can interfere with actions of certain medicines. Garlic and onion supplements can act like blood thinners, and should be avoided when taking medication, as should fish oil capsules. Eating fish and cooking with modest amounts of garlic are perfectly safe.

Bottom line

Be an informed consumer, understand the hidden risks of mixing certain food and medicines. Limit or avoid certain foods when needed, and talk to your doctor or pharmacist for personalized advice.

Madelyn Fernstrom is co-author of "Don't Eat This if You're Taking That." She is health and nutrition editor at NBC News. Follow her at DrFernstrom.