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FOOD/DRUG AND DRUG/NUTRIENT INTERACTIONS:
What You Should Know About Your Medications1
Linda B. Bobroff, Ashley Lentz, and R. Elaine Turner2 Medications, both prescription and over-the-counter, are used every day to treat acute and chronic illness. Research and technology constantly improve the drugs we have available and introduce new ones. Medications can help people live healthy lives for a prolonged period. Although medicines are prescribed often, it is important to realize that they must still be used with caution. Foods, and the nutrients they contain, can interact with medications we take. This can cause unwanted effects. A food/drug interaction occurs when a food, or one of its components, interferes with the way a drug is used in the body. A drug/nutrient interaction occurs when a drug affects the use of a nutrient in the body. This fact sheet describes common food/drug and drug/nutrient interactions. We hope this will help you see the potential for interactions and learn to avoid them. Be sure to talk with your doctor and pharmacist to get the maximum benefits from your medications. How Drugs React in the Body
Risk Factors
In order to understand food/drug and Risk for food/drug and drug/nutrient drug/nutrient interactions, it's important to interactions can be affected by many factors understand how drugs work in the body. There are four stages of drug action for medicines taken by mouth: Stage 1. The drug dissolves into a useable
• medical history form in the stomach. • body composition Stage 2. The drug is absorbed into the blood
• nutritional status and transported to its site of action. Stage 3. The body responds to the drug and
number of medications used the drug performs a function. Stage 4. The drug is excreted from the body
either by the kidney, the liver, or This document is FCS8092, one of a series of the Department of Family, Youth and Community Sciences, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. First Published: March 1999. Revised dates: November 2008; May 2009. Please visit the EDIS Web site a Linda B. Bobroff, PhD, RD, LD/N, professor, Department of Family, Youth, and Community Sciences; Ashley Lentz, MS, former Graduate Student, Food, Science and Human Nutrition Department; and R. Elaine Turner, PhD, RD, Professor and Associate Dean, College of Agricultural and Life Sciences, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611. We thank Paul Doering, UF College of Pharmacy for his review and Laurie Walker, BS, Food Science and Human Nutrition Department for her contributions. The Institute of Food and Agricultural Sciences (IFAS) is an equal opportunity institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. U. S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Millie Ferrer, Interim Dean FOOD/DRUG AND DRUG/NUTRIENT INTERACTIONS: What You Should Know About Your Medications Page 2 Not all medications are taken by mouth. Still, Alcohol can affect many medications. they are all transported to the site of action. Always check with your pharmacist about Effects of drug/nutrient and food/drug possible effects of alcohol on your interactions vary according to: • type of medication • form of drug (pill, liquid, etc.) Grapefruit Juice and Drugs
• site of absorption (mouth, stomach, Grapefruit juice contains a compound that increases the absorption of some drugs. This • route of administration (oral, can enhance their effects. This compound is intravenous, etc.) not found in other citrus juices. It's best to not take medications with grapefruit juice. Drink it at least two hours away from when you take your medication. If you often drink grapefruit juice, talk with Absorption: the passage of substances from
your pharmacist or doctor before changing the GI tract into the blood. Excretion: removal of drugs or nutrients
Intravenous: within the blood.
See Table 1 for specific examples of Nutritional status: nutrition-related health.
food/drug interactions. Transport: movement of a substance from
one site in the body to another. Drug/Nutrient Interactions
It is also possible for drugs to interfere with a person's nutritional status. Some drugs Food/Drug Interactions
interfere with the absorption of a nutrient. Other drugs affect the body's use and/or Foods can interfere with the stages of drug excretion of nutrients, especially vitamins and action in a number of ways. The most minerals. If less of a nutrient is available to common effect is for foods to interfere with the body because of these effects, this may drug absorption. This can make a drug less lead to a nutrient deficiency. effective because less gets into the blood and to the site of action. Second, nutrients or Sometimes drugs affect nutritional status by other chemicals in foods can affect how a increasing or decreasing appetite. This affects drug is used in the body. Third, excretion of the amount of food (and nutrients) consumed. drugs from the body may be affected by Some specific examples of drug/nutrient foods, nutrients, or other substances. interactions are given in Table 2. With some drugs, it's important to avoid taking food and medication together because The Different Groups of Medicines
the food can make the drug less effective. For other drugs, it may be good to take the drug Drugs are grouped into classes based on with food to prevent stomach irritation. illnesses for which they are prescribed. They can also be grouped in other ways, such as FOOD/DRUG AND DRUG/NUTRIENT INTERACTIONS: What You Should Know About Your Medications Page 3 their chemical make-up or actions in the Other drugs like penicillin and erythromycin
body. Different foods can interact with more are most effective when taken on an empty than one class of drugs. stomach. This is because they may be partially destroyed by stomach acid when Table 3 is a list of 14 drug classes and the taken with food. However, food can reduce uses for each. If you take medication in one the chance of stomach irritation from these of these classes, be aware of potential drugs. Ask your pharmacist if you should food/drug and drug/nutrient interactions. If take your particular antibiotic with or without you aren't sure which classes your medicines fall into, ask your doctor or pharmacist. Analgesic
Anticoagulants slow the process of blood Analgesics are drugs that relieve pain. clotting. This can decrease risk of strokes in Analgesics often cause stomach irritation. It's patients whose blood tends to clot too easily. a good idea to take analgesics, like aspirin, These drugs, like warfarin (Coumadin),
with food. A full stomach lowers the risk for work by interfering with the use of vitamin K stomach irritation. in blood clotting. Antacid, Acid Blocker
People taking these anticoagulants should be consistent in the amount of vitamin K they Antacids neutralize stomach acid, and acid get from foods. It's very important to avoid blockers reduce stomach acid production. eating large amounts of foods high in vitamin Long term use of these drugs may lead to K. Rich sources of vitamin K include liver, certain nutrient deficiencies. This is because and green vegetables such as broccoli, stomach acid is important in the digestion spinach and other leafy greens. and/or absorption of nutrients. Older people produce less stomach acid, which leads to low absorption of vitamin B12. Anticonvulsant drugs help control seizures. Regular use of antacids or acid blockers Phenytoin (Dilantin), phenobarbital and
lower B12 absorption even more. Vitamin B12 primidone may cause diarrhea and a
supplements may be needed in this situation. decrease in appetite. This can decrease the availability of many nutrients. Antibiotic
These drugs also increase the use of vitamin Antibiotics are used to treat bacterial D in the body. This means that less vitamin D infections. There are many different types of is available for important functions such as antibiotics. Some antibiotics decrease the calcium absorption. Vitamin D supplements synthesis of vitamin K by the bacteria normally found in our intestines. Vitamin K is important for normal blood clotting. Some anticonvulsants also interact with the B vitamin folic acid. When drug therapy is Tetracycline antibiotics bind to calcium
started, folic acid levels in the body decrease. found in dairy products. This can decrease the Because folic acid supplements affect blood absorption of the antibiotic. levels of the drug, folate supplementation must be supervised by a doctor. FOOD/DRUG AND DRUG/NUTRIENT INTERACTIONS: What You Should Know About Your Medications Page 4 Methotrexate reduces availability of the B
vitamin folic acid. Supplementation of folic Antihistamines are used to treat allergies. acid may be recommended for people taking Many of these drugs often cause drowsiness. this drug, but ask your doctor before starting They may also increase the appetite, which can lead to weight gain. Increased physical activity can help reduce weight gain. Alcohol Diuretic
can cause an even greater increase in drowsiness caused by antihistamines like Diuretics cause the body to excrete more diphenhydramine (Benadryl),
urine and are often used to treat high blood chlorpheniramine (Chlor-Trimeton), and
pressure and fluid buildup. Some diuretics other over-the-counter drugs containing increase urine losses of minerals such as potassium, magnesium, and calcium. Others limit mineral loss (especially potassium). It is important to talk with your doctor about whether you need to take or avoid mineral Anti-inflammatory medication is prescribed to patients for a number of problems such as chronic joint pain, headaches, and arthritis. Laxative
Long-term use may lead to stomach irritation and eventually ulcers. These medications Laxatives speed up the movement of should be taken with food. materials through the digestive tract. This reduces the time for nutrient absorption. Blood Pressure Lowering Drugs
Excessive use of laxatives can deplete vitamins and minerals needed for normal Antihypertensives are used to control high body function. Laxatives also increase fluid blood pressure. This group of medications is losses. This may lead to dehydration. widely used throughout the United States due to the large number of people with high blood Lipid Lowering Drugs
Lipid lowering drugs, also called These medications can affect body levels of Antihyperlipemic drugs reduce blood minerals such as potassium, calcium, and cholesterol levels. Medications such as zinc. For patients with diabetes, these drugs cholestyramine (Questran) may decrease the
can cause problems in controlling blood absorption of the fat soluble vitamins (A, D, sugar. In addition, natural licorice, found in E, and K), vitamin B12, folic acid, and some imported candies, causes salt and water calcium. For long-term use, it may be helpful retention. This can lead to an increase in to take a multivitamin and a calcium Cancer Drugs
Mental Health Drugs
Antineoplastic agents are used to treat Psychotherapeutic drugs treat depression, different forms of cancer. These drugs can anxiety, and other mental health conditions. irritate the cells lining the mouth, stomach, Some of these drugs increase appetite while and intestines. Many cause nausea, vomiting, others decrease it. Either effect can impact and/or diarrhea. All of these can affect weight in a significant way. nutrient status. FOOD/DRUG AND DRUG/NUTRIENT INTERACTIONS: What You Should Know About Your Medications Page 5 Avoid alcohol when using these drugs. Alcohol can intensify the drowsiness caused by this class of drugs. Some psychotherapeutic drugs are Monoamine Oxidase (MAO) inhibitors (see box). MAO Inhibitors
These drugs decrease the body's use of compounds called monoamines. MAO inhibitors can also react with tyramine (a monoamine) found in foods. This reaction can cause a dangerous rise in blood pressure. If not treated, this can cause death. Some aged and fermented foods are high in tyramine. They should be avoided by people taking MAO inhibitors. A few of these foods are: • aged cheese • Brewer's yeast, yeast extracts • Chianti wine • pickled herring • fava beans If you are not sure if you are taking a MOA inhibitor, ask your doctor or pharmacist. Table 1 and Table 2 include major food/drug and drug/nutrient interactions. This is only a sample of the medications and interactions in each category. Check with your doctor or pharmacist for specific information about your medication. FOOD/DRUG AND DRUG/NUTRIENT INTERACTIONS: What You Should Know About Your Medications Page 6 Table 1: Examples of Food/Drug Interactions
Drug Class
Food that Interacts
Effect of the Food
What to Do
Analgesic
acetaminophen (Tylenol) Increases risk for liver toxicity Antibiotic
 tetracyclines  Dairy products; iron  Decreases drug  Do not take with milk. Take 1 hour before or 2 hours after food/milk.  amoxicillin, penicillin,  Decreases drug  Take 1 hour before or 2 zithromax, erythromycin hours after meals.  nitrofurantoin  Decreases GI distress,  Take with food or milk. slows drug absorption Limit foods high in Vitamin K: warfarin (Coumadin) Foods rich in Vitamin K Decreases drug effectiveness liver, broccoli, spinach, kale, cauliflower, and Brussels sprouts Causes increased drowsiness phenobarbital, primidone Decrease in drug effectiveness Avoid excess vitamin C Antifungal
griseofulvin (Fulvicin) Increases drug absorption Take with high-fat meal FOOD/DRUG AND DRUG/NUTRIENT INTERACTIONS: What You Should Know About Your Medications Page 7 Table 1: Examples of Food/Drug Interactions
Drug Class
Food that Interacts
Effect of the Food
What to Do
Increased drowsiness chlorpheniramine (Chlor-Trimeton) Enhances drug absorption lovastatin (Mevacor) felodipine (Plendil), nifedipine Grapefruit juice Increases drug absorption Consult your physician or Pharmacist before changing diet.
Anti-inflammatory
 Food or milk  Decreases GI irritation  Take with food or milk naproxen (Naprosyn), ibuprofen (Motrin)  Increases risk for liver  Damage or stomach  Avoid alcohol Diuretic
Decreases GI irritation spironolactone (Aldactone) Foods high in tyramine: aged cheeses, Chianti wine, pickled isocarboxazid (Marplan), Risk for hypertensive crisis Avoid foods high in tyramine herring, Brewer's yeast, fava tranylcypromine (Parnate), phenelzine (Nardil) FOOD/DRUG AND DRUG/NUTRIENT INTERACTIONS: What You Should Know About Your Medications Page 8 Table 2: Examples of Drug/Nutrient Interactions
Drug Class
Food that Interacts
Effect of the Food
What to Do
Acid Blocker
ranitidine (Zantac),
Consult your physician cimetidine (Tagamet), Decrease vitamin absorption famotidine (Pepcid), 12 supplementation nizatidine (Axid) Fat soluble vitamins Include rich sources of these cholestyramine (Questran), Decreases vitamin absorption vitamins in the diet colestipol (Colestid) Consult your physician Folic acid, vitamin B Decreases vitamin absorption regarding supplementation Diuretic
Include fresh fruits and furosemide (Lasix), Increases mineral loss in urine vegetables in the diet hydrochlorothiazide (HCTZ) Laxative
Consult your physician Vitamins and minerals Decreases nutrient absorption fibercon, Mitrolan regarding supplementation FOOD/DRUG AND DRUG/NUTRIENT INTERACTIONS: What You Should Know About Your Medications Page 9 Table 3: Examples of drug classes and their uses.
Used to treat. .
Antacid, Acid Blocker Stomach upset, ulcers Seizures, epilepsy Antihyperlipemic High blood cholesterol Antihypertensive High blood pressure Anti-inflammatory Fever, inflammation Psychotherapeutic Depression, anxiety FOOD/DRUG AND DRUG/NUTRIENT INTERACTIONS: What You Should Know About Your Medications Page 10 Things to Keep in Mind
• Always read the directions and warning labels on your medication bottles and packages. If As you probably know, there are a wide variety of you don't understand something, ask your medications on the market today. Almost all doctor pharmacist. medications have the potential to cause side effects. Many people take more than one References
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food and drug interactions are more likely to occur. The following tips can help you avoid Drug-Nutrient Resource, 5th ed. Roche Dietitians, problems with your medication. L.L.C., Riverside, IL. 2003. • Always carry a list of all your medications and Physician's Desk Reference 63rd ed. Thomson the dosing instructions. Healthcare, Montvale, NJ. 2009. • When your doctor prescribes a new Food/Drug and Drug/Nutrient Interactions
medication, tell him/her all the other drugs you already take. This includes over-the-counter McCabe, B.J., Frankel, E.H., Wolfe, J.J., eds. drugs and supplements that you use regularly. Handbook of Food-Drug Interactions. CRC Press, Also, remind your doctor about any drug Boca Raton, FL. 2003. allergies you have. Akamine, D., Filho M.K., & Peres, C.M. "Drug- • Know how and when to take all of your nutrient interactions in elderly people." Current medications. If you have any questions, ask Opinion in Clinical Nutrition and Metabolic Care, your doctor or pharmacist. 10:304-310, 2007. • If you have any side effects from a medication, Genser, D. "Food and drug interaction: contact your doctor or pharmacist immediately. Consequences for the nutrition/health status." Do not wait until your next appointment. If you Annals of Nutrition & Metabolism. 52(suppl are not sure if symptoms are related to your medication, be sure to ask. McCabe, B.J. Prevention of food-drug interactions • It is usually best to take medication with a full with special emphasis on older adults. Current glass of water. This may help to prevent Opinion in Clinical Nutrition and Metabolic Care, stomach irritation and improve absorption. Don't take medications with soft drinks or grapefruit juice. Important Drug and Food Information. NIH Clinical Center. • Get your prescription refilled before you run out so that there are no missed doses. • Don't stir your medication into food or drink Food + Drug Interactions. 2004. National unless your doctor or pharmacist tells you to. Consumers League. Certain foods may break down the drug, or limit its absorption. ccessed 1/31/09.

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