Why should we care about nutrient and drug interactions?
A drug is a substance other than food that is intended to affect a structure or function of the body. The term drug includes prescription drugs, over the counter drugs and alcohol. Any person who takes a drug risks potentially harmful effect from food and drug interactions 
Concurrent administration of medication and food may lead to interactions which may alter the metabolism or absorption of the drug or nutrient. Some interactions may have little or no effect while certain interactions are fatal.
A food-drug interaction can:
- prevent a medicine from working the way it should
- cause a side effect from a medicine to get worse or better
- cause a new side effect 
Drug nutrient interactions depends on many factors like age, sex, genetics, body composition, dosage of drug, the way of administering the drug and the disease condition they suffer from. Usually malnourished patients, elderly patients, children, pregnant women are usually on the high risk side for drug nutrient interaction.
Important Interactions one should be mindful
- Grape juice, being touted as nutraceutical as it reduces the incidence of heart diseases, is being stated as nutra pollutical in some people. Grape juice blocks some enzymes in the gut and increases the bioavailability of medicine to our body. This can lead to noxious effect from the drug. Hence statin drugs, psychiatric medications, antihistamines should not be taken with grape juice. 
- Antihistamines are taken to relieve cold, cough, blocked nose, sneezing. Avoid taking alcohol along with these medicines, as they may add to the drowsiness caused by medicine.
- Prolonged intake of aspirin can lead to deficiency of folic acid, as the drug reacts with folic acid and excretes it.
- Anti-infective drugs particularly cloxacillin, ampicillin, pencillin are degraded by acidic food in the stomach hence these drugs should be taken only with full glass of plain water 1 hour before or 2 hours after food.
- The aluminium and magnesium in antacids can form a complex with phosphate and deplete the body. Calcium loss from bones is often a consequence. Anyone at risk of osteoporosis should probably be very cautious
- Broad-spectrum antibiotics can mess up the good intestinal bacteria that make vitamin K. In some people this could lead to unusual bleeding.
- Absorption of Iron tablets is enhanced when it is consumed with fruit juices whereas taking the supplement along with tea reduces absorption of iron. Tannic acid in tea interferes with absorption of iron.
Hence physicians and nurses should do a thorough assessment of the patient before prescribing drugs and an ongoing effort to monitor the status of the patient should be made. A systematic study of the pharmacology literature is also essential to minimise drug nutrient interactions.
- Lutz C, Przytulski K, Food, nutrient and drug interactions, PP351- 363, Nutrition and diet therapy, 2008, Jaypee Brothers Medical Publishing , New Delhi,
- Avoid food – drug interactions – A Guide from the National Consumers League and U.S. Food and Drug Administration Interactions
- William C, Grape juice can interact with medicines, Todays dietician , 2010
- Trovato et al, Drug-Nutrient Interactions, American Family Physician, 1991, vol. 44, pp. 1651-1658