Medicines That Kill: Are You At Risk?

This isn't about the fight against fake drugs, but a more sinister or unexpected; your favourite foods could turn your medicines into a health risk.  Do you think twice about washing down a prescription drug with a glass of grapefruit juice or enjoying a cheese sandwich while taking a course of antibiotics? Probably not.  Perhaps you should. Because taking some prescription drugs with certain foods could lead to dangerous interactions, which could prove fatal in some cases.  A healthcare report suggests that there are over 200 drugs, which can be made toxic or less effective when mixed with ingredients from certain foods.

 Are You At Risk?

Theoretically we are all at risk because some of the most common drugs are susceptible to food interactions as explained below:

Warfarin : shouldn't be taken with cranberry juice because it causes your body to break the drug too slowly, hence making it more potent. Green vegetables increase its metabolism and reduce its efficacy, as can ice cream, soya beans and avocados.

Simvastatins: grapefruit juice makes statins more toxic and can disturb heart rhythms.

Tamoxifen: Phytoestrogen found in soy sauce could possibly react with Tamoxifen.

Paracetamol: Alcohol and cabbage do not mix well with paracetamol because they cause it to break down quickly and become more toxic.

Antibiotics and anti-malarial drugs: Dairy products make these drugs less effective by preventing your body absorbing them.

Oral Contraceptives and Anti-HIV drugs: All these drugs react with St. Johns Wort. In the past two decades, there have been 56 reports on interactions between drugs and herbs, 44 of them concerning St Johns Wort. Sounds ridiculous? No it's not. There’s no need to panic, but simply to be aware and watch out. Most interactions are not fatal, but may just reduce the efficacy of the drug; that is it will take longer to get results.  For instance, if you take a glass of milk after taking an antibiotic, the calcium in the milk will react with the drug, bind to it and stop your body absorbing it, thus reducing its efficacy.  On the other hand, Simvastatins, which are used to lower cholesterol, can become highly toxic when taken with grapefruit juice and could disturb the heart rhythm.

Watch Out for CYP3A4

CYP3A4 is actually a vital enzyme produced by your body.   It is an important part of the liver’s detox system, and almost 50% of the drugs prescribed by your doctors depend on CYP3A4 for proper metabolism. However, the crux of the problem is that some foods can affect how the enzyme works, altering the way your body metabolises the medication and causing the drugs to be broken down and absorbed faster by your body. Consequently, a drug could be less effective or over effective or cause side effects.  The worst food culprit is grapefruit juice, which inhibits CYP3A4 and may make your body absorb drugs faster.  The normal advice is to avoid grapefruit juice when taking a prescription medicine. 

Also high protein diets can have a similar effect on drugs.  If you eat a lot of protein, blood flow increases to your internal organs, so your body absorbs drugs a lot faster that it should do, while, according to a report, a phytoestrogen found in soy sauce could interact with hormone control and Tamoxifen.  

However, on a more positive note, there is no need to worry about interactions with hormone replacement therapy (HRT).  Menopausal symptoms are not life threatening so if a food does interact with HRT, the worse effect would be less efficacy in treating menopausal symptoms.

How to Avoid Food & Drug Interactions

It’s ironic that the major cause for worry here are healthy foods such as grapefruit juice, milk, cranberry juice, even green vegetables which adversely affect the absorption of the drug warfrin. The advice isn't about giving up the benefits of a healthy diet to protect ourselves from possible adverse interactions. The emphasis is simply to adhere to prescription directions.  For instance prescriptions tell you to take a drug either with a meal or on an empty stomach for a very good reason. Often interactions only happen if you take the drug at the same time as the food.

In order to avoid the health hazard of food-drug interaction, it’s crucial to take your drugs as directed by the doctor and the Information leaflet in the box.   There are exceptions of course, for instance some foods really should be avoided if you are on a certain drug.  If you're taking the anti-depressant Monoamine Oxidase Inhibitors (MAOIs) for instance, you should definitely avoid cheese because no matter when you eat it, it could cause a potentially fatal interaction. Also taking multi-vitamins on an empty stomach makes you queasy. That is why the directions is to take it with food or after a meal.

How to stay safe

No need to panic since doctors are kept informed of side effects and interactions and should be able to advise you. Food and drug interactions are rare and most times shouldn’t cause serious problems. However, always discuss your diet with your doctor particularly when you’re on drugs that you think taking them will react negatively with the food you eat regularly. Also ensure your doctor is in the know about any local herbs or supplements you are taking.

Lastly if  your doctor tells you to take a drug on an empty stomach, follow his advice or you risk an interaction.  The same applies if you are advised to take a drug after a meal.

Photo Credit: Creative Commons.