Mixing Food and Drugs

When Food Affects Medicine

Foods can affect drug action in many ways. The most common is when foods interfere with absorption, which can make a drug less effective. For example, calcium in milk can bind to the antibiotic tetracycline, interfering with its absorption. Nutrients or other components of food can also interfere with a drug’s metabolism, or how it is broken down in the body. Finally, foods can affect the elimination of drugs from the body.

So some drugs should not be taken with food. Other drugs must be taken with food to prevent stomach irritation.

When Medicine Affects Nutrients

Some drugs interfere with the absorption of nutrients. For example, some cholesterol-lowering medications reduce the absorption of fat-soluble vitamins. Others affect the body’s use or elimination of nutrients, like diuretics, which can cause a depletion of potassium, and lead to a deficiency.

Dangerous Interactions 

The following are some of the more serious interactions that can occur between food and medicine:

• MAO inhibitors and foods containing tyramine: Mixing monoamine oxidase (MAO) inhibitors—a class of medications used to treat depression—with foods high in tyramine produces one of the most dramatic and dangerous food-drug interactions. Symptoms include a rapid rise in blood pressure, severe headache, collapse and even death. Foods high in tyramine include aged cheese, chicken liver, certain red wines, yeast extracts, processed meats, dried or pickled fish, legumes, soy sauce and beer.

• Grapefruit: Grapefruit juice contains a compound that can increase the absorption of certain drugs, which can result in receiving a larger dose than was intended. This effect is not seen with other citrus fruit juices. Examples of drugs that are affected include AIDS medications, cholesterol-lowering “statins,” calcium channel blockers, antihypertension drugs, and cyclosporine, an immune system suppressant. As a general rule it is better to stay away from taking any medication with grapefruit juice. Since compounds in grapefruit juice can stay in the blood for 24 hours, effects may be noted even if the medication is not taken directly with the juice.

• Foods high in vitamin K: Vitamin K is essential for clotting blood. Foods high in vitamin K, such as Swiss chard, kale, spinach, brussels sprouts, broccoli and other leafy greens, can interfere with blood thinners.

• Alcohol: Alcohol and medications do not mix well. Alcohol can slow down the body’s metabolism, so medications stay active longer than they should. In some cases, mixing alcohol with medication can be fatal. Try to avoid it completely when taking prescription or over-the-counter medications.

High Blood Pressure Drugs and Potassium

Many antihypertensive drugs deplete the body’s reserves of potassium, an electrolyte that maintains the body’s fluid balance and is also essential for nerve and muscle function. People on these medications should eat lots of bananas, citrus and dried fruits, tomatoes, and other potassium-rich foods.

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