There are cases when food and medications clash like mother-in-law and son-in-law at a holiday lunch. It can happen that food alters the way a medication is metabolized, how quickly it enters the bloodstream, or even increases its effect to a dangerous extent. Here we will explain the four most common traps you should be aware of if you want your medications to help you and not harm you.

• Grapefruit Juice: Health in a Glass or Silent Threat?
  
  It's almost ironic that grapefruit, known for helping cleanse the body, boosting immunity, and regulating digestion, can also cause quite a confusion if you are taking certain medications. Grapefruit juice contains substances called furanocoumarins. Although they sound like a magical potion, they are natural compounds that inhibit the enzyme CYP3A4 in the intestines. This enzyme plays a crucial role - ensuring that the medication passes through the liver and is metabolized before fully entering the bloodstream.
  
  If this enzyme is absent or temporarily put to sleep by grapefruit juice, here's what happens: the medication enters the bloodstream much faster and in larger quantities. This means it works too strongly. Scientists from the University of Ontario in Canada have already published that grapefruit juice affects over 85 different medications. Among them are cholesterol-lowering drugs (such as statins), high blood pressure medications (such as calcium channel blockers), anti-anxiety medications (benzodiazepines), and even some medications for suppressing the immune system.
  
  Just one glass (200 ml) of grapefruit juice can cause the concentration of drugs in the blood to increase up to three times - which is already dangerous for many. In practice, this leads to more side effects, from dizziness to liver damage.
  
  
• Bananas: Potassium Queens that Can Surprise
  
  Bananas are the first choice for athletes, elderly people, and anyone who wants natural energy without energy drinks. They contain a lot of potassium - around 422 mg per medium banana, which is about 9% of the recommended daily intake.
  
  However, people taking blood pressure-lowering medications need to be cautious. In particular, it concerns medications called ACE inhibitors, such as enalapril and ramipril. These medications help dilate blood vessels and lower blood pressure, but they also increase the potassium levels in the blood. If you also consume a lot of bananas, oranges, or spinach, the potassium level could become too high.
  
  The consequence? It could lead to arrhythmia, irregular heartbeats, often starting with a feeling of the heart "skipping" or "fluttering". A study published in the American Journal of Medicine showed that in patients taking ACE inhibitors and consuming a diet high in potassium-rich foods, the risk of heart complications is more than 3 times higher.
  
  Bananas also contain tyramine. It is a natural substance also found in red wine, aged cheese, soy products, and sausages. Tyramine can cause a dangerous increase in blood pressure in those taking MAO inhibitors - older but still used antidepressant medications. If you take such medications, opt for an apple over a banana.
  
  
• Spinach: Health Ally or Hindrance in Treatment?
  
  Our grandparents swore by spinach - for a reason. It is rich in vitamin K, which the body needs for bone formation, proper liver function, and blood clotting. But here lies the problem.
  
  If you are taking blood thinners - the most well-known being warfarin - then vitamin K can reduce their effectiveness. Warfarin inhibits the action of vitamin K to prevent the blood from becoming too thick and causing clots. However, if you consume significant amounts of this vitamin through spinach, broccoli, or kale, you could neutralize the effect of the medication.
  
  Some patients taking warfarin may experience bleeding, while others may face dangerous blood clotting. A study in the British Journal of Clinical Pharmacology showed that 40% of people on warfarin do not have a stable INR level (a measure of how quickly the blood clots) precisely due to dietary habits.
  
  This doesn't mean you should completely avoid spinach, but it is essential to maintain a consistent intake of vitamin K. If you eat spinach three times a week, make it a habit rather than having it for five days in a row and then nothing for two weeks.
  
  
• Fiber: Wonderful for Digestion, but Can Slow Down Medications
  We are also big advocates of fiber - it aids in digestion, regulates blood sugar, and lowers cholesterol. Whole grain bread, beans, apples, oats - all food that the heart and intestines love.
  
  But here too lies a trap. Fiber slows down stomach emptying and thus the absorption of medications. For example, if you take an antibiotic and eat a whole grain bar, the medication may not enter your bloodstream quickly enough or in sufficient quantities.
  
  Some antibiotics, such as tetracyclines and quinolones, are highly sensitive to this. The US Food and Drug Administration (FDA) has issued several warnings in the past decade that fiber, as well as calcium, magnesium, and iron, can reduce the effectiveness of antibiotics by more than 50%. Therefore, it's not surprising that doctors recommend taking medications at least one hour before or two hours after a high-fiber meal.

What's Next?

In our daily lives, we often make mistakes because no one has informed us in time. Sometimes food and medications don't get along, and even though each works therapeutically on its own, in the wrong combination, they can cause harm.

It's not about stopping eating fruits, vegetables, or fiber. The key is knowing how to combine, when to take medications, and when to eat certain foods. And of course, if you're unsure, always consult a doctor or pharmacist.

Lastly, a tip from folk wisdom: He who knows what goes into his mouth doesn't always need medication. Sometimes just the awareness of what we eat and when can do more than the most expensive pill.