When a doctor prescribes medication, he usually informs the patient about instructions on how to take it, whether it should be given with meals or on an empty stomach... but he/she rarely refers to the foods with which the medication can or cannot be combined.
As María del Carmen Lozano Estevan, Food and Nutrition Vocal of the Official College of Pharmacists of Madrid (COFM) and Head of Pharmacy Studies at the Alfonso X el Sabio University in Madrid explains, "Food and medicine are destined to suffer interactions". This mutual relationship can occur in two directions: that drugs modify the normal absorption of nutrients or that foods alter the effectiveness of drugs.
In the first case, as the expert points out, the prescribed treatment can even lead to vitamin or mineral deficiencies. This is the case, for example, with isoniazid - a drug normally indicated to treat tuberculosis - which, in prolonged use, lowers vitamin B6 levels.
In the second case, it is the food that affects the effectiveness of the therapeutic substances. "The effect may be greater or less, or appear later than expected," says Lozano Estevan. A good example is the mixing of drugs, such as benzodiazepines and statins - for example, diazepam - with grapefruit, a citrus fruit that decreases the liver's ability to eliminate the drug, and consequently increases its action or toxicity. Other drugs that interact with grapefruit are antihypertensives, calcium channel blockers, antihistamines and immunosuppressants. Sometimes, according to the Food and Nutrition vowel of COFM, "the pharmacological response and the nutritional value of the food can be affected at the same time, as occurs, for example, with the combined intake of tetracyclines - a group of antibiotics - and dairy products". In this case, the absorption of both calcium and the drug will be lower than expected.
And what drinks go best with medication?
The expert assures that, although there are no general guidelines and each case must be evaluated, "as a general rule, the combined use of drugs with milk, tea, coffee and fibre and mineral supplements should be avoided". For example, acidic liquids degrade antibiotics before they reach the stomach. Although not all interactions are negative: "Iron absorption is increased by the presence of foods rich in vitamin C," says Lozano Estevan.
Right on time
We must not only look at what the drugs are taken with but when they are ingested. "When administering a drug by mouth, it's important to know whether it should be taken with meals (at the beginning, during or at the end) or on an empty stomach (an hour before or two after intake)," says Lozano Estevan. The fact is that often mixing the medicines with meals can diminish the therapeutic action; while at other times, ingesting them on an empty stomach can injure the stomach or attenuate the effect, as Lozano Estevan recalls. When in doubt, always listen to the information in the advertisements and consult your pharmacist.