May 1, 2019

Foods and Medicines

The “grapefruit diet”?

Peter N. Landless & Zeno L. Charles-Marcel

Q:I follow the “grapefruit diet” to lose weight (fat). But my skeptical daughter says that grapefruit and some of the supplements I take can cause problems with my medicines. Is this true?

A:Your daughter is correct. Some “things we ingest” (TWIs), such as foods, beverages, herbs, and supplements, may affect how prescribed or over-the-counter medications work. We strongly encourage discussing all of your medications, supplements, and herbals with your doctor and pharmacist, who need to know what you are taking so they can advise you accordingly.

Amazingly, most medications and TWIs have unnoticeable or insignificant interactions with each other. The potential problem is that while medications are assumed to be given appropriately, and in safe doses for legitimate medical indications, they may interact with TWIs by increasing or decreasing their potency, or may augment or mask side effects. Medications may also affect a person’s nutrition by altering the absorption, utilization, or elimination of vitamins, minerals, and other food components. Additionally, herbal supplements (e.g., ginseng and Saint-John’s-wort) can negatively interact with other medicinal compounds.

If you are taking medicines for high blood pressure, high cholesterol, anxiety, allergies, or irregular or abnormal heartbeat, your grapefruit diet may be problematic, depending upon the specific medication, the amount of grapefruit in the diet, and your own genetics. Grapefruit, pomelos, and tangelos typically let more of the drugs they interact with enter the blood.

Medications Affected by Consuming Grapefruit
Amiodarone (Cordarone®)Lovostatin (Mevacor®)
Atorvastatin (Lipitor®)Nifedipine (Procardia®)
Buspirone (Buspar®)Sertraline (Zoloft®)
Carbamazepine (Corbatrol® Tegretol®)Sildenafil (Viagra®, Revatio®)
Fexofenadine (Allegra®)Simvastatin (Zolcor®)

For example, your “grapefruit diet” can cause increased absorption and blood levels of certain statin drugs (used to lower cholesterol), increasing your risk for liver and muscle damage that can lead to kidney failure. On the other hand, grapefruit (as well as oranges and apples) may cause less Allegra (fexofenadine) to enter the blood and decrease its effectiveness.

Grapefruit can be part of a nutritious diet, but even small amounts (six ounces of juice) affect how certain medications work for 24 hours. Grapefruit may reduce insulin resistance and promote lower all-day calorie intake, but similar weight loss is seen with water or grapefruit or grapefruit juice taken 20 minutes before meals.

You are commended for moving to a healthier weight; this is good, even though there is debate about the benefits of the “grapefruit diet” per se. A comprehensive lifestyle modification with sound nutrition, exercise, sleep, and water—yielding to the Holy Spirit for promptings and power—is a wise and wholesome investment of time and energy.

Medication Safety Tip: Always talk with your doctor before taking something new. Read labels and package inserts, directions, and warnings for possible interactions. Ask your pharmacist or doctor if you don’t understand something. Do not take capsules apart, mix medicines and supplements together, crush medicines, or dissolve medicines in food or drink unless you are directed to do so. These actions can change how the medications work. Never take medicines with alcohol (we advise that no one ever consume alcohol).* A full glass of water is best, unless told to do otherwise.

* See


Peter N. Landless, a board-certified nuclear cardiologist, is director of the General Conference Health Ministries Department. Zeno L. Charles-Marcel, a board-certified internist, is an associate director of Adventist Health Ministries at the General Conference.