Food and Drugs You Don't Want to Mix

March 17th 2017

Kyle Jaeger

People are frequently warned about the risks of mixing prescription medications and alcohol, or combining pharmaceuticals without consulting a doctor. But fewer people have heard about the dangers of mixing certain drugs with common foods or drinks.

Here are some foods and drinks you want to avoid when taking specific medications.

Opioid Pills

1. Grapefruit


In 2012, researchers at the Lawson Health Institute Research Center compiled a list of more than 85 drugs that interact with whole grapefruit, or grapefruit juice. That list includes common medications such as prescription painkillers, cholesterol-lowering agents, and allergy drugs such as Allegra.

That's because grapefruit contains the chemical compound furanocoumarins, which inhibits an enzyme that helps metabolize toxic substances. When you consume furanocoumarins, that can cause a buildup of toxic ingredients from pharmaceuticals in your bloodstream, NBC News reported.

2. High-fiber foods (e.g. spinach)


Foods that contain high concentrations of fiber causes the stomach to empty faster, leading to slower absorption of medications. Basically, fiber makes it so that less of the drug you take is absorbed into your bloodstream, which could render the substance ineffective. Fiberous foods are particularly problematic for people taking antibiotics like penicillin, according to the Food and Drug Administration (FDA).

3. Hard cheese

blue cheese

If you're taking a monoamine oxidase inhibitors (MAOI) antidepressant, it's best to avoid cheeses such as cheddar, Swiss, parmesan, Stilton, Gorgonzola, and Camembert. Hard or strong cheeses have high levels of tyramine, an amino acid that regulates blood pressure. Because MAOIs block the enzyme monoamine oxidase, which removes excess tyramine from the body, eating these cheeses can result in an unsafe concentration of tyramine remaining in your bloodstream. 

The combination can "cause a serious spike in blood pressure and require emergency treatment," according to the Mayo Clinic.

4. High-vitamin K foods (i.e. broccoli)


Vitamin K promotes blood clotting, which is beneficial unless you're taking blood thinners such as Warfarin or Dalteparin. Eating foods that have high concentrations of vitamin K such as kale or broccoli can counteract the blood thinning effects of these drugs.

"The adequate intake level of vitamin K for adult men is 120 micrograms (mcg). For adult women, it's 90 mcg," Dr. Sheldon Sheps wrote in a warning about the drug interaction. Though he added that "eating small amounts of foods that are rich in vitamin K shouldn't cause a problem."