Doctors warn these common foods and drinks could affect your medication's effectiveness

Most people are pretty set in their eating habits — they have their go-to snacks, a specific morning coffee order, favorite dinner recipes and more.

Beware, though: Some foods and drinks that seem perfectly innocuous can actually disrupt how common prescriptions work. This is known as a food-drug interaction. Anyone who’s on a prescription, and specifically a new prescription, should talk to their doctor to learn when is the best time to take the medication and if any food or drinks should be avoided, said Dr. Chris Scuderi, a family physician in Florida.

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“You want to understand what you’re taking and how best to take it to make sure that the medication is as safe as it could be and works as planned,” he noted. Certain foods and drugs can make medications too strong or too weak, potentially leading to health issues.

Supplements and vitamins can also interact with diet choices, said Dr. Kitty O’Hare, the senior medical director for pediatrics at Duke Primary Care in North Carolina.

Below, doctors share the most common foods and drinks that interact with prescriptions. Here’s what to know:

1. Grapefruit

Grapefruit is “one of the more widely known interactions out there,” O’Hare said. Yes, grapefruit is healthy, but it binds to a digestive enzyme that “helps with digesting some medications,” O’Hare explained.

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“If you are drinking grapefruit juice or eating grapefruit while taking some medications, that can actually cause the levels of those medications to rise in your blood and make the medications stronger and sometimes give more side effects,” O’Hare continued.

This affects certain statin cholesterol medications along with some blood pressure medications, according to Scuderi. Grapefruit can also interfere with some psychiatric medications.

This does not apply to all cholesterol, blood pressure or psychiatric medications, though; it’s best to talk to your doctor to see if any of your specific prescriptions are affected by grapefruit. 

2. Leafy green vegetables

Leafy green vegetables ― such as kale, spinach, broccoli and collard greens ― are high in vitamin K and can make some blood thinners less effective, O’Hare said.

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For people who are on these medications, it’s important that they eat a “very similar amount of green, leafy vegetables every day,” said Scuderi.

If you’re someone who has one salad a day but increases to three, that could be a problem. Similarly, if you never eat leafy green veggies but start a daily broccoli habit, it could also be dangerous.

These kinds of diet changes can change how potent the medication is, Scuderi noted. This can “increase either their bleeding risk or increase their clotting risk,” he added. 

The concern doesn’t apply to all blood thinners, but if you are on a blood thinner or get prescribed one, it’s worth talking to your doctor about any risks that come with leafy green veggies.

3. Certain dairy products

Dairy can interact with a whole host of common prescriptions, including some thyroid medications and osteoporosis medications, Scuderi said. 

“Sometimes dairy products, when taken close in time to antibiotics ... the calcium in dairy products might make the antibiotics temporarily less effective,” said O’Hare.

Depending on the medication you’re prescribed, you may be instructed by your doctor or pharmacist to separate it from dairy products.

4. Bananas, avocados and other potassium-rich foods

“Some blood pressure medications cause your body to hold on to potassium and to have a little bit higher levels of potassium,” O’Hare explained. “If you’re eating a lot of potassium-rich foods like bananas and avocados, that could actually make your potassium levels too high.”

This isn’t true for all blood pressure medications, but is true for some, which makes it valuable to talk to your doctor about your specific situation. 

5. Alcohol

Alcohol interacts with many medications, O’Hare stressed.

“[Alcohol] may increase the potential for side effects for certain medications like sleepiness, drowsiness or confusion, so it’s always wise to be thoughtful about alcohol intake when taking medications, and to consult your doctor about what’s best for your health,” she said. 

“Alcohol is a big one, especially for people who are on some of the controlled medications such as sedatives, opioids, other medications what we call our central nervous system depressants,” Scuderi noted. Alcohol can further depress this function, which manages our movements, thoughts and feelings.

“Really, if you’re on those types of medications, you want to avoid alcohol with those,” Scuderi said.

6. Caffeine

Coffee and energy drinks may not be ideal for people on some prescriptions, too.

If you’re on certain medications, particularly stimulants like those used for ADHD, caffeine can potentially “increase palpitations or make people feel tremors or feel more anxious,” according to Scuderi.

Good news: Some foods and drinks help medications work better.

There are other foods and drinks that can potentially interact with prescription medications in the opposite way.

“Sometimes food can have a positive effect,” Scuderi said. “So, you think about people who are iron-deficient; vitamin C has been shown to improve how iron is absorbed.” Many folks who are iron-deficient are told to take their iron supplement with orange juice or an orange because of this.

In the end, talk to your doctor or pharmacist about your prescriptions and any potential food interactions. 

If you’re on a prescription, it’s best to talk to your doctor or pharmacist to ensure you’re consuming (or avoiding) the right ingredients and taking your medicine at the ideal time.

Little changes can help your medications be more effective and help you reach your health goals.

“There are a lot of possible interactions and many unique circumstances, which is just why it’s important to keep your doctor and pharmacist in the loop about what foods and drinks you like best,” O’Hare said.