Whether on a short-term course of antibiotics, or a long-term treatment like warfarin, you always want to be taking your medication safely and as instructed. But that can be easier said than done if youāre not aware of the food-drug interactions you can experience on your medication.
Thatās where we come in. Weāve put together a guide on some of the most common food-drug interactions to help you stay safe ā the answers may surprise you!
Three key takeaways
A drug-food interaction is when your medication interacts with food or drink, potentially making it less effective or increasing the chance of side effects.
Grapefruit is one of the most common causes of food and medicine interactions.
Always make sure to read the patient information leaflet for guidance on what to avoid when taking your medication.
What is a drug interaction?
A drug interaction is when somethingĀ interacts with your medication. This can then changeĀ how effectivelyĀ the drugĀ works, or increase theĀ chance of you experiencing side effects.Ā
There are three main types of drug interactions:
Drug-drug interactions: this is when the drug you are taking interacts with another medicine you may be on.
Drug-condition interactions: this is when your medication interacts with a pre-existing medical condition you may have.
Drug-food interactions: this is when your medication interacts with food or drink.
Food and medicine interactions
One of our prescribing pharmacists, Ian Budd, has put together a list of some of the mostĀ common foods and drinks that can interfere withĀ everydayĀ medication.Ā
Grapefruit
If you enjoy some grapefruit over breakfast, you should be aware that, whether in segments or as a juice, itās one of the most common causes of food and medicine interactions.
Grapefruit contains natural chemicals that block an enzyme in your liver that helps break down certain medicines. When that happens, your body canāt process the drug as it normally would, so more of it stays in your system. That can make side effects stronger or more likely.
This is especially important if youāre taking medicines like statins, blood pressure tablets, some antidepressants, immune-suppressing drugs, or erectile dysfunction pills such as sildenafil or tadalafil. Even one glass of grapefruit juice can have an effect that lasts for up to one day, so itās safest to avoid it completely with these medications.
Leafy greens
āLeafy greens like spinach, kale, and broccoli are full of vitamin K, which plays a big role in helping your blood to clot. Warfarin works by slowing down vitamin Kās effect, which is how it helps prevent blood clots.
āSo, if you suddenly eat a lot more (or a lot less) vitamin K-rich foods than usual, it can throw off the balance and make warfarin either less effective (if you eat more greens) or too strong (if you suddenly cut them off).
āThis is why pharmacists always recommend keeping your intake consistent rather than avoiding greens altogether.ā
Ian Budd, Prescribing Pharmacist at Chemist4U
Cranberry juice
Cranberry juice is often seen as a healthy choice, but it can be a problem if youāre taking warfarin. Cranberries contain natural compounds that can affect how your body breaks down warfarin, which may make the drug stronger than intended. That means your blood could become thinner, increasing the risk of bruising or bleeding.
Itās not an issue for everyone, and an occasional glass is unlikely to cause harm, but drinking cranberry juice regularly or taking cranberry supplements can be risky if youāre on warfarin. Itās always best to check with your pharmacist before making it part of your daily routine.
Dairy products
āMilk, cheese, and yoghurt are part of a healthy diet, but they can sometimes get in the way of how certain antibiotics work. The calcium in dairy products can bind medicines like tetracyclines and fluoroquinolones, that are often used to treat chest or urine infections. When that happens, the medicine isnāt absorbed properly, which means your body doesnāt get the full dose and the infection might take longer to clear.
āIf youāre prescribed one of these antibiotics, donāt worry ā you donāt need to avoid dairy altogether. Just try to take your dose a couple of hours before or after having milk or dairy foods so it can do its job properly.ā
Ian Budd, Prescribing Pharmacist at Chemist4U
Tyramine-rich foods
Foods like aged cheeses, cured meats, and fermented products contain something called tyramine. And tyramine can cause a sudden rise in blood pressure if youāre taking older antidepressants known as MAO inhibitors. This type of reaction can make you feel unwell with headaches, a fast heartbeat, or even very high blood pressure.
These drugsĀ arenātĀ prescribed as often now, but for anyone taking them,Ā itāsĀ important to know which foods to avoid. Your pharmacist can help you spot tyramine-rich foods and give simple swaps so you can still enjoy your meals safely.Ā
Alcohol
Alcohol is one of the most common things that interacts with medications, and the effects can vary depending on what youāre taking. It can make some drugs, like antidepressants, sedatives, and strong painkillers, much more sedating, which can leave you feeling drowsy or unsteady.
It can also put extra strain on your liver or interfere with how medicines for diabetes work, making blood sugar harder to control.
And by mixing Viagra and alcohol at the same time, you may reduce the chance of the erectile dysfunction medication actually working.
It doesnāt mean you can never drink, but itās always worth checking your patient information leaflet or asking your pharmacist whatās safe for you. Knowing how alcohol might affect your medication can help you make more confident, informed choices.
How to keep safe when taking medication
āAsĀ pharmacists, our goalĀ is to help people understand how to use medications safely and effectively, and food plays a bigger role than many people realise. Even choices we think are healthy, like fruits, vegetables, or supplements, can sometimes affect how your medication works or how well your body absorbs it.Ā Ā
āFor example, something as simple as having grapefruit juice with breakfast can interfere with blood pressure medication, antidepressants or cholesterol medication, while foods high in vitamin K can impact how blood thinners work. These are small details, but they can make a real difference in how well your treatment does its job.
āKnowing what to look out for means you can take control of your health and get the most out of your treatment. The more you understand how your medication fits into your daily routine, the safe and more effective it becomes.ā
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