Medication Management: Five Foods That Commonly Interact With Drugs

There are things in life that do not go together. This includes medications that can cause negative interactions when taken together. It also includes different foods that can cause negative interactions with medications. In this article, we discuss five foods that more commonly cause negative interactions with different types of medications.

The five foods that commonly cause negative interactions with a relatively significant number of medications include:

  • Grapefruit
  • Cranberry juice
  • Bananas
  • Leafy greens
  • High-fiber content foods and supplements

As you may see, these items can be a part of a healthy diet. Medication management may require you to consider substitutes for food items that historically have been part of your efforts to maintain a healthy diet. We consider each of these items and why they can cause negative interactions with certain types of medications.


There are some excellent health benefits associated with eating grapefruit. These include vitamin C, potassium, and fiber. Despite these benefits, even small amounts of grapefruit juice can interfere with important intestinal enzymes. This means that grapefruit can alter how the human body metabolizes some medications.

Grapefruit products are contraindicated for patients who are taking certain prescription drugs, including medications frequently taken by seniors. These include (but are not limited to):

  • Statins (Lipitor, Mevacor, Zocor)
  • Immunosuppressants (cyclosporine)
  • Calcium-channel blockers (Adalat, Afeditab, Procardia, Plendil)
  • Psychiatric medications (BuSpar, Zoloft)
  • Benzodiazepines (Valium, Triazolam, Halcion)

Kelly O’Connor, RD, LDN, CDE, outpatient oncology dietitian at the University of Maryland Upper Chesapeake Health System’s Kaufman Cancer Center, warns that there are instances in which a person might not be aware of the presence of grapefruit. For example, sodas like Squirt and Fresca can also contain grapefruit juice. For this reason, it is important to check beverage labels carefully.

Cranberry Juice

Urinary tract infections (UTIs) are a common and potentially serious problem for seniors. Many family caregivers use home remedies like cranberry juice or cranberry extract to prevent and manage recurrent UTIs. You need to remember that this juice contains chemicals that may interact negatively with warfarin (Coumadin) and some other statin medications.

This fact underscores the need to consult your doctor before using home remedies to treat a condition when taking medications. You also need to be sure that you fully understand what foods or beverages are contraindicated for a particular drug when you start taking a medication.


Bananas are another food item with tremendous health benefits. Bananas are rich in potassium. In addition, research shows that bananas are an excellent choice to reduce the risk of:

  • Cancer
  • Stroke
  • Heart disease

Bananas can be contraindicated for a person taking certain medications designed to lower blood pressure. These medications also reduce potassium excretion via urination.

According to the U.S. Food and Drug Administration or FDA, people need to avoid bananas when taking medications that include:

  • ACE inhibitors (Lotensin, Capoten, Zestril)
  • ARBs (Cozaar) may develop hyperkalemia (elevated potassium levels) and dangerous heart palpitations if they over-indulge in potassium-rich foods (the risk is particularly increased for elders who have impaired kidney function.

Bananas also contain tyramine, an amino acid found in red wine, soy, and certain cheeses. This amino acid can interact negatively with monoamine oxidase inhibitors or MAOI. MAOIs, which include Nardil and Parnate, are a class of medications that are commonly prescribed to treat depression.

Leafy Greens

Food items like spinach, kale, cabbage, and broccoli receive high marks regarding healthy eating. These vegetables are rich in the following:

  • Vitamin K
  • Other minerals
  • Fiber

In addition, they are low in unhealthy calories.

Despite these benefits, people taking blood thinners (like warfarin) and eating too much of these types of vegetables can have negative consequences. For example, vitamin K promotes blood clotting. This might work to counteract the blood-thinning benefits of anticoagulant medications.

Remember that taking blood thinners doesn’t mean seniors must dodge healthy food choices. Generally speaking, it is acceptable for people using these medications to consistently eat a moderate amount of leafy greens like spinach. An example of moderate consumption is a one-half cup two to three times a week. The key is communicating with the prescribing doctor about a person’s usual diet.

High-Fiber Content Foods and Supplements

A healthy diet depends on an appropriate amount of fiber. The fiber found in whole grains, vegetables, and fruits, is an important element of a nutritious diet. Research has demonstrated that fiber can play a role in reducing the risk of heart disease and diabetes. It can also help relieve constipation and promote healthy weight management.

Fiber also slows the rate at which a person’s stomach empties. This also slows the rate at which medications are absorbed. This can potentially lower blood levels of specific prescriptions, including antibiotics. This slowing effect is magnified with fiber supplements like Metamucil and Citrucel.

It’s important to understand that the average American doesn’t get the recommended daily amount of dietary fiber from the food they eat. Therefore, if a person is considering a fiber supplement, it is important to first consult with a doctor to ascertain whether that might negatively impact any medications being taken.

In conclusion, any time a doctor considers adding a medication to an older individual’s drug regimen, the physician must be aware of all prescription drugs, over-the-counter, and dietary supplements being utilized. This vital information exchange reduces the risk of unhealthy interactions between a medication and something else, including certain food items.

As noted in this article, an older person does not always have to stop eating a particular type of food altogether. Moderating intake may be sufficient to avoid some negative interactions.  

An older individual or his or her caregiver should never hesitate to talk to a doctor about any questions or concerns associated with diet and lifestyle and their impact on a prescription drug regimen. In addition, it is crucial to read medication labels and inserts thoroughly.