Nutrient-Drug Interactions

Nutrient Drug Interactions 2129
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Medications have become an integral part of life for many people. Medicine serves to help people when they are sick, allowing them to live longer and healthier lives. With rapidly growing research and technology, medications are more beneficial, and new ones continue to be discovered. Drugs do need to be taken with caution, however. All medications, whether prescribed by a doctor or bought over-the-counter , are capable of harmful side effects. The foods people eat contain nutrients that are used by the body to produce energy . Sometimes, certain medications may interact with both the food eaten and the nutrients the food gives to the body for proper functioning. When the body is unable to use a nutrient due to a drug that has been taken, a nutrient-drug interaction has occurred.

Function of a Drug

A drug is taken to prevent or treat sickness and disease. It is important to know what happens in the body when a drug is taken in order to better understand the interaction between nutrients and drugs. The action of a drug taken orally generally occurs in four steps: (1) the drug dissolves in the stomach, (2) the drug is absorbed into the blood and moves via the blood to the area of the body that needs it, (3) the body reacts to the medicine, and (4) the body gets rid of the drug by way of the kidney, liver, or both.

Adverse Effects of Nutrient-Drug Interactions

A nutrient-drug interaction may impact the body in several ways. Certain foods can affect the rate at which the body uses a medication. A drug will not work as well if a certain nutrient in a food speeds up or slows down the


Drug Indication Possible Effects
SOURCE : Compiled from references in the bibliography.
Coumadin Anticoagulant (blood thinner) Vitamin K is a nutrient in the body that helps blood to clot. Vitamin K is present in foods such as green, leafy vegetables and fish. It will interfere with a blood thinner like coumadin.
Dilantin Anticonvulsant (anti-seizure) Vitamin D and folic acid levels in the body are decreased by the taking of these types of drugs.
Norvasc Antihypertensive (for high blood pressure) Consuming foods high in sodium (i.e., licorice, processed meats, canned foods) will decrease the effectiveness of the drug.
Aspirin Anti-inflammatory/pain reliever Taking large amounts of these drugs will cause a loss of Vitamin C in the body.
Birth control pills Oral contraceptives Women who take these drugs often have low levels of folic acid and Vitamin B 6 in the blood.
Dyazide/Thiazide Diuretics (water-eliminating) Taking diuretics often leads to a loss of potassium in the body.
Tetracycline Antibiotic Calcium may interact with the effectiveness of the antibiotic. Avoid dairy products for two to three hours before and after taking the medicine.
Lipitor/Zocor Statins (cholesterol-lowering drugs) Antioxidants (Vitamin A, C, E, B, folic acid) may interact with the drug by reversing its effect.
Prednisone Corticosteroid The drug may increase appetite thus increasing nutrient intake.
Lasix Diuretic (water-eliminating) The drug may decrease appetite thus decreasing nutrient intake.

Some drugs may affect the absorption of nutrients, while some foods—for example, those containing caffeine—can amplify or modify the effects of certain drugs. Taking drugs with hot beverages could also make them less effective. [Octane Photographic. Reproduced by permission.]
Some drugs may affect the absorption of nutrients, while some foods—for example, those containing caffeine—can amplify or modify the effects of certain drugs. Taking drugs with hot beverages could also make them less effective.
[Octane Photographic. Reproduced by permission.]

drug's absorption into the body. Short- or long-term instances of nutrient-drug interactions may be life threatening. A nutrient-drug interaction may also impact the nutritional status of the body. Nutrient-drug interactions can occur with both prescription and over-the-counter medicine.

Impact of Food on Effectiveness of a Drug

A medication has ingredients, just as food does, that allow it to function correctly when taken in order to help the body in some way. A food may interfere with the effectiveness of a drug if the food interacts with the ingredients in the medication, preventing the drug from working properly. Nutrients in food may either delay absorption into the body or speed up elimination from the body, either or which can impact a drug's effectiveness. For example, the acidic ingredients in fruit juices are capable of decreasing the power of antibiotics such as penicillin. Tetracycline, another infection-fighting drug, is impacted by the consumption of dairy products. Many medications that are taken to fight depression can be dangerous if mixed with beverages or foods that consist of tyramine, which is found in items such as beer, red wine, and some cheeses.

Food can also impact the effectiveness of a drug due to the way it is consumed. Generally, medicine is to be taken at the same time food is eaten. This is because the medicine may upset the stomach if the stomach is empty. However, sometimes taking a drug at the same time that food is eaten can interfere with the way the medicine is absorbed by the body.

Impact on Nutritional Status

A drug has the capacity of interfering with a person's nutritional status. Appetite may be stimulated by a certain drug, resulting in an increase in nutrient intake due to more food being eaten. However, drugs may also cause a decrease in appetite, leading to a decrease in nutrient intake. In this case, a drug could possibly cause a nutritional deficiency. Nutritional status may also be impacted by a drug's effect on the three main nutrients: carbohydrates , fat , and protein . A drug may speed up or slow down the breakdown of these three nutrients, which are essential to the body's functioning. When a drug affects the absorption of nutrients from food into the body, less energy is available to be used by the body. The impact of the nutrient-drug interaction may vary according to the medicine taken, the dose of the medicine given, and the form taken (e.g., pill, liquid).

The Elderly and Nutrient-Drug Interactions

Elderly persons are at a significant risk for nutrient-drug interactions. This population often takes the highest amount of medications, and with the use of multiple drugs, certain problems may exist. A loss of appetite, a reduced sense of taste and smell, and swallowing problems all may result from medication use in elderly people.

Malnutrition is a common problem among older adults. Therefore, nutritional status may be already impacted by decreased nutrient intake. This may only worsen the effect of a possible nutrient-drug interaction. Elderly people who take many drugs on a routine basis for long periods of time are at greatest risk of nutrient depletion and nutritional deficiencies .

Tips for Avoiding Interactions

There are ways to avoid placing the body at risk of an unwanted nutrient-drug interaction. The following are tips to remember about taking medications and will help avoid interactions:

  • Be sure to read the label on a prescription medicine and ask a pharmacist or physician if something is not clear.
  • Read all directions, warnings, and any possible side effects printed on all drug labels and information in the package.
  • Always take medications with a full glass of water.
  • A drug may not work correctly if a medicine is taken improperly; do not stir medication into food or take apart capsules (unless told to do so).
  • Take vitamin and mineral supplements before or after medicine, as they may interact with certain drugs.
  • Avoid stirring drugs into hot drinks such as coffee because the drug's effectiveness can be destroyed by the hot temperature.
  • Do not drink alcohol when taking any medicine.
  • Always tell a physician and pharmacist about all medicines being taken, including both prescription and over-the-counter drugs.

SEE ALSO Adult Nutrition ; Alternative Medicines AND Therapies ; Nutrients ; Nutritional Deficiency .

D. Michelle Swords


Alonso-Aperte, E., and Varela-Moreiras, G. (2000). "Drugs-Nutrient Interactions: A Potential Problem during Adolescence." European Journal of Clinical Nutrition 54:S69–S74.

Heimburger, Douglas C., and Weinsier, Roland L. (1997). Handbook of Clinical Nutrition, 3rd edition. St. Louis, MO: Mosby.

Mahan, L. Kathleen, and Escott-Stump, Sylvia (1996). Krause's Food, Nutrition, and Diet Therapy, 9th edition. Philadelphia: W. B. Saunders Company.

Roe, Daphne A. (1994). "Medications and Nutrition in the Elderly." Primary Care 21:135–147.

Worthington-Roberts, Bonnie S., and Rodwell Williams, Sue (1996). Nutrition throughout the Life Cycle, 3rd edition. Boston: WCB/McGraw-Hill.

Internet Resources

College of Agricultural Sciences, Penn State Unviersity. "Facts about Food/Drug Interactions." Available from <>

University of Florida, Cooperative Extension Service, Institute of Food and Agricultural Sciences. "Food/Drug and Drug/Nutrient Interactions: What You Should Know about Your Medications." Available from <>

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