How Food-Drug Interactions Can Impact Your Diet When Taking Medication

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Food-drug interactions occur when certain medications interact poorly with different foods, drinks or supplements you might consume. These interactions are often listed as general warnings on prescription bottles or as advised by your pharmacist. When not taken seriously, they can counteract a drug’s ability to work.

Rebecca Trepasso, RD, a clinical dietitian for Henry Ford Health, explains why it is so important to follow medication recommendations to avoid diminishing the effectiveness of a drug.

“Often, different foods can either speed up or slow down your body’s ability to process certain medications,” says Trepasso. “This can allow either too much or too little of a drug into your system – which can have adverse effects, especially if you are taking that medicine for a specific health issue or medical condition.”

Common Food-Drug Interactions To Avoid

Just as different medications have different effects on the body, not all foods interact with drugs the same way. Here is a list of common food-drug interactions that can take place when these foods are consumed:

  • Grapefruit and grapefruit juice. Grapefruit products interact with an enzyme in the body responsible for breaking down drugs which can cause dangerously high levels of medication in your blood. Avoid if you are taking statins (for high cholesterol), calcium channel blockers (for high blood pressure) or have recently had an organ transplant.
  • Alcohol. Talk to your doctor before consuming alcohol when taking any type of medication. Some medications can make you drowsy and when combined with  alcohol, can increase your chance of injury if you try to operate a vehicle or machinery. Others can make you feel the effects of alcohol more quickly. Alcohol should also be avoided when taking over-the-counter pain medications as it can increase your chances for liver damage.
  • Dairy. Diary products like milk, cheese and yogurt are high in calcium. Some antibiotics can bind with calcium in the stomach and small intestine to create a substance that the body is unable to absorb, decreasing the medicine’s effectiveness.
  • Iodine-rich foods. Iodine is an element found in foods (seafood, iodized salt, eggs, dairy) that is necessary for your thyroid to function. However, if you have hyperthyroidism, or an overactive thyroid, a diet high in iodine can lessen the effectiveness of your thyroid medication.
  • Foods high in vitamin K. Vitamin K can be found in leafy greens such as kale, spinach and collard greens. Too much of it can lessen the effectiveness of aspirin and blood thinners.

“Talk with your doctor before making any serious modifications to your diet – especially if you are on a specific diet due to a health condition or food allergies,” says Trepasso. “Also, consult with your doctor before self-prescribing any vitamin or herbal supplements.” Supplements are not FDA-regulated and can also cause serious food-drug interactions when consumed in concentrated doses.

Additionally, many drugs can have a poor interaction with you body if consumed on an empty or full stomach. When prescribed a new medication, talk with your doctor or pharmacist about dosage instructions and possible food-drug interactions. Following these directions closely increases the effectiveness of the medication and can avoid causing further injury or illness due to improper usage.


To find a doctor or registered dietitian at Henry Ford, call 1-855-434-5483 or visit Nutrition Services on henryford.com.

Rebecca Trepasso, RD, is a clinical dietitian who sees patients at Henry Ford Hospital.

Categories: EatWell