10 Commonly Prescribed Medications and the Foods That Should Be Avoided with Them

It is understood that a well-balanced diet is part of a healthy lifestyle. However, what is often overlooked is that the way we eat and drink may interfere with the medications in our regimen.

In the US, 48.6% of Americans have taken at least one prescription drug in the last 30 days, while nearly one-quarter of Americans have taken three or more. Of the top 200 most commonly prescribed medications, 166 are taken orally. This means that, like food, they must pass through the gastrointestinal tract. Consequently, the presence of certain nutrients from foods in the stomach or intestine may change the efficacy or pose a safety risk for the patient.

[signup]

Overview of Food-Drug Interactions

A food-drug interaction is defined as an outcome between active compound(s) in a food and a medication. Since over 80% of the drugs most often taken in the US are administered by mouth, this means that when food is taken at or around the same time, the food could interfere with the way the drug is absorbed, broken down, and eliminated in the body. Also referred to as a pharmacokinetic interaction, it could result in the effect of the drug having more or less than the desired effect in the body–potentially resulting in an adverse event or side effect.  

While not all prescribed medications are affected by food, many are not only affected by the food itself but also the time of day in which it is consumed. Some medications are recommended to be taken with food, while others are not. Determining the instructions on how and when to take your medications for optimal effectiveness should be discussed with your healthcare team before beginning any new prescription.

10 Commonly Prescribed Medications and the Foods That Should Be Avoided with Them

Read on for a list of medications that you may be taking that interact with familiar foods.

Medication 1: Digoxin (Lanoxin)

Digoxin is a cardiac glycoside prescribed as one of the agents in a heart failure or atrial fibrillation regimen. When digoxin is taken orally, it has 60-80% bioavailability. When it is administered with meals containing high bran fiber (like oatmeal), the amount absorbed may be reduced, meaning that its desired efficacy may be lowered. 

One study showed that there was a statistically significant decrease in absorption for the duration of the study, while another showed that there was a statistically significant decrease in plasma concentration at week 2 that decreased further by the four-week mark. A third study showed that when separating the digoxin and fiber by 30 minutes, it had no difference in digoxin efficacy.

Medication 2: Tetracycline Antibiotics

Tetracyclines are a class of antibiotics that are prescribed to adults to treat infections and certain skin conditions, like acne. Examples include but are not limited to doxycycline, demeclocycline, and minocycline. Studies recommend that when taking this class of antibiotics, they are separated at least one hour before and two hours after ingesting milk, yogurt, other dairy products, or antacids. When taken together, studies report that due to tetracycline’s high affinity to bind to the calcium-rich products, it can hinder absorption by 50-90%. One study found that a small quantity of milk added to coffee or tea severely impacted the drug’s absorption.

Medication 3: Monoamine Oxidase Inhibitors

A class of antidepressants called monoamine oxidase inhibitors, or MAOIs, include the drugs tranylcypromine (Pamate), selegiline (Emsam), isocarboxazid (Marplan), and phenelzine (Nardil). Foods that should be avoided when taking them include those considered high in tyramine: aged cheeses, wine, pickled fish, fermented foods, cured meats, soy products, brewer’s yeast, and more. Taking these foods with MAOIs can result in a rapid increase in blood pressure, referred to as a hypertensive crisis. This is generally paired with symptoms that may include headache, nausea, vomiting, sweating, chest pain, and fast heart rate. 

Medication 4: Statins

Statins are a group of medications that inhibit a specific enzyme, HMG CoA reductase, resulting in helping to lower LDL (low-density lipoproteins), also known as bad cholesterol. Some statins–specifically, atorvastatin (Lipitor), simvastatin (Zocor), and lovastatin (Mevacor)–are impacted by grapefruit juice, while other statins are not. 

Grapefruit is a potent inhibitor of the CYP3A4 enzyme. Because CYP3A4 is a predominant enzyme involved in breaking down atorvastatin, simvastatin, and lovastatin, it does not allow the natural process of metabolizing them. This means that there can be higher than desired levels of drug in the body, which could result in adverse events.

Studies show that the bioactive compounds found in grapefruit, called furanocoumarins, are the leading cause of this interaction. If you cannot live without your daily glass of fresh grapefruit juice, it is possible that you can switch to one of those that do not interact. Consult your healthcare provider or pharmacist for more information.

Medication 5: Calcium-channel blockers

Like statins, calcium-channel blockers should not be taken concomitantly with grapefruit juice either. Prescribed drugs in this class–amlodipine (Norvasc), diltiazem (Cardizem), and verapamil (Verelan)–are used to treat heart-related ailments such as blood pressure, chest pain (also known as angina), and irregular heartbeat (also known as arrhythmia). Studies have shown that taking verapamil and diltiazem with grapefruit juice results in the breakdown of the drugs, leading to an increased chance of side effects.

Medication 6: Bisphosphonates

Bisphosphonates, such as alendronate, ibandronate, and risedronate, are first-line prescription medications for treating osteoporosis and other diseases that impact bone density and strength. When taken orally, they should be taken on their own. Studies show that when taken with any food or beverages, it drastically reduces the drug’s absorption and effectiveness. 

Bisphosphonates should be taken upon waking either alone or on an empty stomach, before breakfast, tea, or coffee. A study of patients taking risedronate or placebo between meals or before eating or drinking at the start of the day showed an improvement in bone mineral density in the morning group.

Many patients with osteoporosis may also be taking vitamin D and calcium supplements for bone health. If this is the case, they should be taken at least thirty minutes after alendronate and risedronate and at least one hour after ibandronate.

Medication 7: Levothyroxine (Synthroid)

Levothyroxine is prescribed to patients who have an underactive thyroid to elevate thyroxine (T4) levels in the body. It should be taken on an empty stomach in the morning, at least 30 minutes before breakfast. 

As mentioned on the drug label, levothyroxine can interact with foods such as soy products, certain nuts, and dietary fiber and may inhibit absorption and decrease bioavailability in the digestive tract. 

Drug dosage should be adjusted if these foods are to be consumed within less than one hour of levothyroxine. Interestingly, many systematic reviews and meta-analyses (like this one) do not support the label and claim that the primary literature does not support the FDA’s decision to include it in the label. 

Medication 8: Warfarin (Coumadin)

Perhaps the most infamous of all medications for its drug interactions is warfarin, a commonly prescribed anticoagulant (sometimes referred to as a blood thinner). 

Warfarin is considered a medication with a narrow therapeutic index, meaning that small changes in the dose can result in adverse events and/or therapeutic inefficacy. This means that throughout warfarin treatment, patients should maintain a consistent diet, particularly in the consumption of Vitamin K and protein. 

A high protein diet has been linked to a rise in serum albumin levels and CYP450 enzymatic activity, leading to a change in the international normalized ratio (INR), affecting the effect of warfarin in the body. Some green leafy vegetables (like broccoli, kale, parsley, and spinach) that are high in Vitamin K content should also be consumed with consistency, rather than avoided completely from a nutrient perspective. 

Medication 9: Spironolactone (Aldactone)

Spironolactone is a drug commonly known as a ‘water pill’. It is generally prescribed to patients with heart failure and high blood pressure but has also been used more recently for off-label purposes, like hair growth. Its mechanism of action involves the inhibition of the binding of aldosterone to receptors in the renal tubule and therefore serves as a potassium-sparing diuretic. 

When taken orally, due to its ability to increase potassium levels, it is recommended to avoid salt substitutes (as most of them contain potassium instead of sodium), and not to consume too many potassium-rich foods such as avocados, bananas, coconut water, spinach, and sweet potato. This is especially important for patients with kidney concerns, such as those with end-stage renal disease. 

Medication 10: Ziprasidone (Geodon)

Ziprasidone, also sold under the brand name Geodon, is an atypical antipsychotic that works as an H1 receptor antagonist and is indicated for schizophrenia and bipolar disorder. When taken orally, studies show that when taken with food, it can increase the drug’s absorption up to two-fold. 

Specifically, a crossover study found that when taken with at least 500 kcal, regardless of the fat content, it resulted in maximum efficacy. When the dose response was evaluated, it underscored that the efficacy of the prescribed dose of oral ziprasidone depends on a minimum of 500 kcal consumption. 

Shockingly, the label states that it should be taken with food, so it is recommended to clarify with your healthcare provider or pharmacist if they have further guidance regarding what type or what quantity of food should or should not be taken with a drug. 

This food-drug was included in this article to demonstrate that not all interactions are unwanted or bad. The term interaction determines the relationship between the food and drug consumed. In this case, studies showed that taking ziprasidone with food was not only recommended, but rather a requirement for the optimal effect. 

General Guidelines for Managing Food-Drug Interactions

When determining whether you should eat a food with a prescribed medication, keep the following in mind:

• When visiting your healthcare provider or picking up your prescription at the pharmacy, ask if any foods may interact with new medications. 
• Always read the label carefully. Many prescription drug labels have stickers and reminders regarding foods that should or should not be consumed when taking the medication.
• Unless instructed by your healthcare provider or pharmacist, do not crush or open capsules to take them. Not adhering to the directions on the label or guidance from your healthcare team may hinder the drug’s ability to exert its effect. 
• You (or your caretaker) should keep an updated log–in a notebook or digitally–of the medications, over-the-counter, vitamins, minerals, and herbal products you take regularly. Bring this list to every appointment with your healthcare provider to easily reference it and avoid any potential interactions.
• Keep all of your medications organized in the original pill bottle from the pharmacy. 
• Double-check with your healthcare team before taking certain vitamins, minerals, or other supplements at the same time as taking drugs. Like some foods that may interact with drugs, these products may also decrease their efficacy.
• Fill all of your prescriptions at one pharmacy. 
• Beyond foods, do not forget that beverages could also influence medications. Do not take any prescription medications with alcohol.
• Maintain a consistent diet while taking medications. If you adjust your dietary preferences or habits, inform the healthcare team to ensure that new nutrients from foods or beverages do not interfere with your regimen.

[signup]

Key Takeaways

It is important to understand that there are common foods–like dairy, oatmeal, cured meat, cheese, leafy greens, and more–that should not be taken with certain medications.

Food-drug interactions may result in negative effects on the safety and efficacy of the drug while also playing a role in the patient’s nutrition profile.

Please note that this list is not comprehensive, as there could be other medications that interact with other foods in your daily routine. 

Functional medicine physicians and pharmacists are trained to take a personalized approach to understand how prescription medications may interact with your diet and lifestyle. If you would like to learn more, reach out to your healthcare provider or pharmacist.