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Food & Drug Interactions

What is a food-drug interaction?

A food-drug interaction happens when the food you eat affects the active ingredients in a medicine you are taking so the medicine does not work the way it should.  In a broader sense it happens when both food and drugs are taken at the same time and one affects the way the body utilizes the other.

Are all medicines affected by food?

The interactions will vary according to the dosage, age, sex and overall health. Disease conditions and allergies can also affect the outcome. Not all medicines are affected by food, but many medicines can be affected by what you eat and when you eat it. For example, taking certain medicines with your meal may interfere with the way your stomach and intestines absorb the medicine. Intake of food, beverages, alcohol and dietary supplements may alter the effects of drugs a person takes.

Certain foods may also delay or decrease the absorption of the drug. This explains why some medicines should be taken on an empty stomach (1 hour before eating or 2 hours after eating). On the other hand, some medicines, for example those which irritate the stomach, are easier to tolerate when taken with food. Ask your doctor whether your medicine should be taken with a snack or a meal or on an empty stomach.

Dietary supplements, including medicinal herbs, are products that contain a vitamin, mineral, herb, or amino acid and that are intended as supplements to the normal diet. Supplements are regulated as foods, not as drugs, so they are not tested as comprehensively. However, they may interact with prescription or over-the-counter drugs. People who take dietary supplements should inform their doctors, so that adverse interactions can be avoided.

Alcohol affects body processes and interacts with many drugs. For example, taking alcohol with certain antibiotics can cause flushing, headache, palpitations, nausea and vomiting. Doctors or pharmacists can answer questions about possible alcohol and drug interactions.

Some Food – Drug Interactions

Any food Bisphosphonates Food, even orange juice, coffee, or mineral water, may markedly reduce the absorption and effectiveness of these drugs.
Foods high in vitamin K (such as broccoli, brussels sprouts, spinach and kale) Anticoagulants Such foods may reduce the effectiveness of anticoagulants (such as warfarin) increasing the risk of clotting. Intake of such foods should be limited, and the amount consumed daily should remain constant.
Grapefruit juice, Pomelo and Seville Oranges (Bitter Oranges)
  • Certain benzodiazepines (such as triazolam)
  • Calcium channel blockers (such as felodipine, nifedipine, and nisoldipine)
  • Cyclosporine Estrogen and oral contraceptives
  • Certain statins (such as atorvastatin, lovastatin, and simvastatin)
Grapefruit juice contain furanocouramins which can inhibits cytochrome P450 enzymes involved in drug metabolism and thereby intensifies the effect of certain drugs.
Oatmeal Digoxin The fiber in oatmeal and other cereals, when consumed in large amounts, can interfere with the absorption of digoxin.
Foods high in tyramine, including many cheeses (such as processed, cheddar, blue, brie, mozzarella, and Parmesan), yogurt, sour cream, cured meats (such as sausage and salami), liver, dried fish, caviar, avocados, bananas, yeast extracts, raisins, sauerkraut, soy sauce, fava beans, red wine, certain beers, and products containing caffeine. Mono Amine Oxidase (MAO) inhibitors (e.g phenelzine, tranylcypromine ) These foods reduce effectiveness of the drug. Severe headache and a potentially fatal increase in blood pressure (hypertensive crisis) can occur if people taking an MAO inhibitor (used most often to treat depression) consume these foods. These foods must be avoided.
Calcium or foods containing calcium, such as milk and other dairy products. Tetracycline These foods can reduce the absorption of tetracycline.

Tips to remember about food-drug interactions

  • Read the prescription label on the container.
  • Read all directions, warnings and interaction precautions printed on the medicine labels and packages.
  • If you do not understand something, ask your doctor or pharmacist.
  • Take the medicine with full glass of plain water, unless your doctor tells you differently.
  • Do not stir medicine into your food or mix into hot drinks because this may change the way the drug works.
  • Never take any medicine with alcoholic drinks.
  • If you have an allergy to any food or drug, please inform your doctor.
  • If you are on multiple drugs, please consult your doctor on any precautions and possible interactions.


Last reviewed : 3 April 2014
Writer : Dr. A’aisah bt. Senin
Reviewer : Pn. Norrani binti Eksan