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FCS8092
FOOD/DRUG AND DRUG/NUTRIENT INTERACTIONS:
What You Should Know About Your Medications1
Linda B. Bobroff, Ashley Lentz, and R. Elaine Turner2
Introduction
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.
such as: There are four stages of drug action for
medicines taken by mouth:
• age
• gender 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.
• number of medications used Stage 3. The body responds to the drug and
the drug performs a function.
Stage 4. The drug is excreted from the body
either by the kidney, the liver, or
both.
1. 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 at http://edis.ifas.ufl.edu
.
2. 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
Archival copy: for current recommendations see http://edis.ifas.ufl.edu or your local extension office.
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: medication.
• type of medication
• form of drug (pill, liquid, etc.) Grapefruit Juice and Drugs
• dosage
• site of absorption (mouth, stomach, Grapefruit juice contains a compound that
intestine) 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
Definitions grapefruit juice. Drink it at least two hours
away from when you take your medication.
Absorption: the passage of substances from If you often drink grapefruit juice, talk with
the GI tract into the blood. your pharmacist or doctor before changing
your routine.
Excretion: removal of drugs or nutrients
from the body.
Intravenous: within the blood.
Nutritional status: nutrition-related health. See Table 1 for specific examples of
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
May 2009
Archival copy: for current recommendations see http://edis.ifas.ufl.edu or your local extension office.
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 food.
fall into, ask your doctor or pharmacist.
Anticoagulant
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.
Anticonvulsant
Older people produce less stomach acid,
which leads to low absorption of vitamin B Anticonvulsant drugs help control seizures.
Regular use of antacids or acid blockers 12. Phenytoin (Dilantin), phenobarbital and
lower B absorption even more. Vitamin B primidone may cause diarrhea and a
12 12
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 may be needed.
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.
May 2009
Archival copy: for current recommendations see http://edis.ifas.ufl.edu or your local extension office.
FOOD/DRUG AND DRUG/NUTRIENT INTERACTIONS: What You Should Know About Your Medications Page 4
Antihistamine 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 folic acid.
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
antihistamines. potassium, magnesium, and calcium. Others
limit mineral loss (especially potassium). It is
Anti-inflammatory important to talk with your doctor about
whether you need to take or avoid mineral
Anti-inflammatory medication is prescribed supplements.
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
pressure.
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 B , folic acid, and
12
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
blood pressure. supplement.
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.
May 2009
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