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Does food influence the effects of medications?

Published on February 14, 2020 at 14:07 / Updated on June 7, 2022 at 13:31

Have you ever been told that mixing grapefruit juice with your medications is dangerous for the body? This article takes a look at the question and delves deeper into it. For example, can certain specific food groups cause adverse health effects when taken in conjunction with certain classes of medications? If so, why, and what are the risks? Let's take a closer look at a subject more complex than it seems.

Food-drug interactions

We talk about food-drug interactions when the food we eat can modify the body's response to medication. In fact, it can act on the different stages through which the medication passes when taken orally. Thus, its absorption, distribution, metabolism and elimination may be affected. More specifically, it most affects the medications’ bioavailability - the fraction of an administered dose that is actually absorbed by the body. When food-drug interactions occur, the medications’ bioavailability s altered, resulting in variations in drug concentration, efficacy, or toxicity. In addition, food influences the action of medications by attenuating, reducing or enhancing their pharmacological and side effects.

The following people are most at risk of being exposed to food-drug interactions:

  • Older people taking multiple medications
  • People who have had a transplant
  • People with cancer
  • People that are HIV positive
  • Undernourished people.

Should the medication be taken on an empty stomach or with food?

When medication is recommended to be taken with a meal, it’s often in order to reduce the side effects. This is because food helps protect the stomach from the irritating effects of certain pain medications, such as ibuprofen and naproxen. Specifically, stomach upset, gastric reflux, nausea and vomiting may be alleviated if the medication causing these symptoms is taken with food.

On the other hand, it’s sometimes better to take your medication a few hours before or after eating. When a medicine is taken orally, it needs to pass through the bloodstream to exert its effect. To achieve this, it must be absorbed by the walls of the digestive system. As food must follow the same path as medications in the body, its presence can compromise, among other things, its degree of absorption. Below are some food groups that are not recommended for joint intake of certain types of medication.

Medication interactions with grapefruit

Studies on drug interactions with grapefruit are numerous and have shown that about 85 medications available on the market are likely to interact with this food, due to the fact that it inhibits hepatic drug metabolism. Therefore, it creates an increased concentration of the medication and an increased risk of side effects that can lead to serious complications. People over 45 who are taking multiple medications are most at risk for these interactions.  

In particular, people taking medications in the following classes should check with their healthcare professional before consuming grapefruit, in any form, within two hours of taking the medications, and limit consumption of grapefruit juice to a maximum of ¼ liter per day:

  • Statins
  • Antihypertensives
  • Antianginal medications
  • Immunosuppressants
  • Antidepressants
  • Anti-infectives
  • Calcium channel blockers
  • Benzodiazepines

Other citrus fruits can also interact with medications, like Seville oranges, limes and pomelo. Most other citrus fruits don’t interact with medications.

Dairy products and medications

Dairy products are usually high in calcium, and this can interfere with the absorption of some medicines. In fact, since calcium is a positive ion, it tends to bind to a negative ion. A complex then forms, whose volume becomes too large and consequently cannot be absorbed by the small intestine. This causes the medication to be excreted in the stool rather than delivered to its site of action. For example, medications that may bind to calcium should generally be taken one to two hours before or after meals. These include bisphosphonates, which treat osteoporosis, and certain antibiotics, such as tetracycline,, ciprofloxacin and norfloxacin.

Interaction between blood thinners and foods rich in vitamin K

People taking warfarin (Coumadin), or other anti-vitamin K-type anticoagulants, should pay special attention to any foods containing significant amounts of vitamin K in their diet. In fact, anticoagulants are prescribed to thin the blood and prevent clots from forming. Since they prevent the production of vitamin K, foods rich in vitamin K therefore have the effect of countering their action, rendering anticoagulants ineffective. Thus, for people taking warfarin, it’s not a question of eliminating the intake of foods rich in vitamin K, but of maintaining stable consumption to prevent potentially dangerous imbalances.  

Below is a list of foods to watch out for:

  • Green vegetables (Brussels sprouts, broccoli, cabbage, lettuce, spinach, etc.)
  • Green tea
  • Seaweed
  • Offal
  • Soybean and rapeseed oil
  • Lentils

Alcohol and medication

Combined with certain medications, alcohol can reduce alertness and cause drowsiness. It’s also known to promote the absorption of liposoluble - i.e. fat soluble - medications and potentiate their effects:

  • Tranquilizers (anxiolytics, such as benzodiazepines)
  • Hypnotics
  • Neuroleptics
  • Antidepressants
  • Central analgesics (tramadol)
  • Antiallergic medications

Also, a cocktail of alcohol and anti-inflammatory drugs (like ibuprofen) or aspirin can cause heartburn and acid reflux. Lastly, certain medications reduce the metabolism of alcohol, resulting in an increase in its toxicity. This increase in toxicity usually occurs with the following medications: 

  • Disulfiram
  • Metronidazole
  • Cephalosporins
  • Sulphonylureas

Some tips to avoid the harmful effects of food-drug interactions:

  • Consult your pharmacist.
  • Drink water when taking medication.
  • Carefully read the medication’s label.
  • Be aware that some nutrients in supplements and natural health products can interact with medications.
  • Maintain a list of medications used, including over-the-counter medications, and specify what they are taken with.

In short, it’s true that food can influence the effect of medications by compromising or promoting their absorption and metabolism. However, you should not ban all foods that cause drug interactions. You just need to eat them a few hours apart from taking the medications and to limit their consumption, when necessary. The goal is always to have a varied and balanced diet. Also, it’s important to remember that a multitude of medications can be taken regardless of the presence of food, or not. In addition, there’s no universal rule to follow when it comes to food-drug interactions and, when in doubt, your pharmacist remains your best ally to provide you with information on the subject and answer your questions. 

Familiprix in collaboration with Hubert Cormier

The drugs and pharmaceutical services featured on the website are offered by pharmacists who own the affiliated pharmacies at Familiprix. The information contained on the site is for informational purposes only and does not in any way replace the advice and advice of your pharmacist or any other health professional. Always consult a health professional before taking or discontinuing medication or making any other decision. Familiprix inc. and the proprietary pharmacists affiliated with Familiprix do not engage in any way by making this information available on this website.