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Food-drug interactions

Rohini Diniz


Every day, millions of people all over the world take both prescription and over-the-counter medications to treat acute and chronic illness. Medicines are like a double edged sword- of great benefit if used correctly, but can be cause harm if incorrectly used. This article aims to enlighten the readers about the interactions of food-drug and drug-nutrients but should not be treated as a substitute for your doctor’s advice.

The foods that we eat can affect the way medicines (drugs) work in the body.  A food – drug interaction is a reaction that occurs when a food, or one of its components, interferes with the way a medicine or drug is used in the body. A drug/nutrient interaction on the other hand occurs when a drug affects the use of a nutrient in the body.

In order to understand food-drug and drug-nutrient interactions, it is important to understand how drugs work in the body. There are four stages of drug action for medicines taken orally:

Stage 1: The medicine dissolves into a useable form in the stomach.

Stage 2: The medicine is absorbed into the blood and transported to its site of action.

Stage 3: The body responds to the medication and the medicine performs a function.

Stage 4: The medicine is excreted from the body either by the kidney, liver, or both.

The effects of food-drug and drug-nutrient interactions vary according to the type of medication; the form of the medication (pill, capsule, liquid, powders etc.) the dosage; the site of absorption (mouth, stomach, intestine) and the route of administration whether oral, intravenous, inhaled etc.

Foods can interfere with the stages of drug action in a number of ways, the most common being interference with the rate of absorption of the medication. If the body cannot absorb as much of the medicine as it should, one will not get the full effect of the medicine as less amount of the medicine has reached the site of action. Conversely if the body absorbs too much of the medicine it can cause the medicine to have an effect that is too strong. Food and nutrients can also affect the excretion of drugs from the body.

Now coming to the question should medicines be taken before or after food? The answer is different for different medicines. Some medicines cause irritation to the lining of the stomach and hence need to be taken along with meals or immediately after a meal up to a maximum of half an hour after the meal.

There are other medicines that need to be taken on an empty stomach preferably one hour before food/snacks or at least two hours after food/snacks because the presence of food may delay, reduce or increase the absorption of medicines.

Medicines can also decrease or increase the amount of nutrients in your body.  Some medicines affect nutritional status by increasing or decreasing appetite which in turn affects the amount of food and nutrients consumed. There are other medicines that reduce the absorption of nutrients or deplete the body of nutrients especially when taken for a long time. For example diuretics which increase urination result in the loss of potassium in the urine there by causing the body potassium levels to be low.

People who are at increased risk for drug-nutrient interactions include young children, pregnant women; older adults, people who are suffering from chronic conditions such as diabetes or heart disease, those who are malnourished and those who take two or more medicines at the same time.

Before you visit a doctor make sure you carry the list of all the medicines including the multivitamin and other supplements you are already taking with the details of the dosage and how often you take them. When your doctor prescribes a new medicine for you, be sure to ask doctor to provide clear instructions for how the medicine should be taken and if there are any foods and/or drinks to avoid while taking the medicine. Also talk to your doctor about the risk of drug–drug interaction and drug-nutrient depletion.

If you are taking a medicine that can affect the amount of a nutrient in your body, your doctor will regularly check your levels and may prescribe a supplement to help keep the nutrient level up while you are taking your medicine.


To be continued . . .

(The Writer is a Consultant Nutritionist practising in Panaji and Margao)


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