Oil and water. Toothpaste and orange juice. Some things just don’t go together. While you’re not likely to get seriously ill from downing a glass of OJ right after brushing your teeth, other seemingly safe combinations can be harmful.

For example, nutritious foods and prescription medications seem like a match made in healthful heaven, right? Not necessarily. According to board-certified family physician and chief medical officer of Vireo Health, Stephen Dahmer, M.D., food and drinks can affect how much of a medication is absorbed and how quickly it is metabolized by the body. These food-drug interactions can render a prescription ineffective or increase its absorption and the risk of dangerous side effects. Dahmer explains some common food-drug interactions that seniors and caregivers should be aware of below.

5 Foods That Can Trigger Food-Drug Interactions

  1. Grapefruit and Grapefruit Products

    Vitamin C, fiber and potassium are just a few of the health perks of eating grapefruit. However, even small amounts of grapefruit juice can interfere with important intestinal enzymes and change how some medications are metabolized by the body. Grapefruit products are contraindicated for patients who are taking certain prescription drugs like statins (Lipitor, Mevacor, Zocor), immunosuppressants (cyclosporine), calcium-channel blockers (Adalat, Afeditab, Procardia, Plendil), psychiatric medications (BuSpar, Zoloft) and benzodiazepines (Valium, Triazolam, Halcion). Dahmer says that consuming grapefruit with any of these medications may increase the risk of side effects and adverse events.
    Kelly O’Connor, RD, LDN, CDE, outpatient oncology dietitian at the University of Maryland Upper Chesapeake Health System’s Kaufman Cancer Center, warns that certain sodas like Squirt and Fresca can also contain grapefruit juice, so it’s important to carefully check beverage labels, too. She offers a straightforward solution for enjoying the health benefits and flavor profile of grapefruit without the risk: swap it with another citrus fruit, such as oranges, lemons, limes or some combination of these.
  2. Bananas

    A potassium powerhouse, bananas are typically a good choice for those seeking to reduce their risk of cancer, stroke and heart disease. However, eating too many potassium-rich foods like bananas, oranges and green, leafy vegetables can be problematic if a person is taking ACE inhibitors or angiotensin receptor blockers (ARBs). Designed to lower blood pressure, these medications also reduce potassium excretion via urination. According to the FDA, people taking ACE inhibitors (Lotensin, Capoten, Zestril) or ARBs (Cozaar) may develop hyperkalemia (elevated potassium levels) and dangerous heart palpitations if they over-indulge on potassium-rich foods. This risk is increased for elders who have impaired kidney function.
    Bananas also contain tyramine, an amino acid found in red wine, soy and certain cheeses that can negatively interact with monoamine oxidase inhibitors (MAOIs). MAOIs (Nardil, Parnate) are a class of drugs commonly prescribed to treat depression. O’Connor says that a low-tyramine diet is typically recommended for people taking these medications.
  3. 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, but this juice contains chemicals that may interact with warfarin (Coumadin) and some statin medications.
  4. Leafy Greens

    Spinach, kale, cabbage and broccoli receive high praise in health food circles for their vitamin K content, minerals, fiber and low calorie count. But, for people taking blood thinners like warfarin, munching on too much green can be bad.
    Dahmer warns that vitamin K promotes blood clotting, which may counteract the blood-thinning benefits of anticoagulant drugs. However, taking blood thinners doesn’t mean that seniors must forgo healthy food choices. According to O’Connor, it’s okay for people on these medications to consume a moderate amount of leafy greens like spinach consistently (for example, a one-half cup serving two to three times a week). The key is to communicate with the prescribing doctor about one’s usual diet and they will tweak anticoagulation therapy to fit one’s lifestyle factors and prevent blood clots.
  5. High-Fiber Foods and Fiber Supplements

    Dietary fiber, the kind found in whole grains, vegetables and fruits, is an important part of a nutritious diet. In fact, fiber has been proven to play a role in reducing the risk of heart disease and diabetes. It can also help relieve constipation and promote healthy weight management. But, because fiber slows the rate at which the stomach empties, Dahmer cautions that it may also slow the rate at which medications are absorbed, resulting in lower blood levels of certain prescriptions, such as antibiotics. This 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. Talk to your physician about your fiber intake and whether you take a fiber supplement. It is unlikely that you need to avoid high-fiber foods, but you may need to adjust when you take your supplement and medication(s).

Manage Medications Responsibly

Any time a doctor adds a medication to your regimen, inform them of all prescription drugs, over-the-counter (OTC) medications and dietary supplements you are already taking to ensure everything fulfills its intended purpose and to minimize the possibility of adverse reactions.

You don’t always have to swear off a particular type of food just because it may interact with your medications. To explore how specific medicines interact with common foods, other drugs, alcohol and even herbal supplements, use the drug interactions checker on Drugs.com.

Don’t hesitate to talk to your doctor about any questions or concerns you may have about how your diet or lifestyle may impact your prescription drug regimen. He or she may be able to recommend alternative medications that do not require dietary restrictions.

Be sure to thoroughly read the labels and inserts that come with all medications to learn what foods and drinks to avoid (if any) and whether they should be taken with food or on an empty stomach. If you need to review a medication insert, visit the U.S. Food & Drug Administration (FDA) website to search their extensive medication guide database.


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Lastly, Dahmer offers one more tip to family caregivers and seniors alike: Take medications with plenty of water to help aid absorption and reduce stomach upset.