A leading doctor has issued a vital warning to the hundreds of thousands of Britons taking anticoagulant medication, stating that a common 'healthy' vegetable could dangerously interfere with their treatment.
The Hidden Risk in Your Salad Bowl
Dr Chris Steele, appearing on ITV's This Morning on 21st December 2025, highlighted the potential for everyday foods to disrupt the effects of crucial medicines. He specifically cautioned patients on blood thinners, such as warfarin, rivaroxaban, and apixaban, about their consumption of leafy green vegetables.
These drugs are prescribed to prevent life-threatening blood clots, strokes, heart attacks, pulmonary embolisms, and deep vein thrombosis. They work by inhibiting the body's clotting process. However, Dr Steele explained that leafy greens like spinach, kale, and cabbage are rich in vitamin K, which naturally promotes blood clotting.
"Warfarin is designed to prevent the production of vitamin K - so if you suddenly eat more greens, this will interfere with the medicine," he stated. The key is not to eliminate these nutritious foods but to maintain a steady, consistent intake to avoid sudden fluctuations in the medication's effectiveness.
Beyond Greens: Other Dietary Dangers
Dr Steele's advice extends beyond salad ingredients. He identified several other common foods and drinks that require caution for those on anticoagulants.
Patients should avoid large amounts of cranberry juice or cranberry products, as they can alter warfarin's effects. He also recommended limiting garlic and ginger, as they may increase the risk of bleeding.
Other foods high in vitamin K that require consistent consumption include:
- Other green vegetables (e.g., broccoli, Brussels sprouts)
- Egg yolks
- Chickpeas and lentils
A Wider Warning on Food and Drug Mix-Ups
The interaction between diet and medication is not limited to blood thinners. Dr Steele provided further crucial guidance for users of other common prescriptions.
He noted that calcium in dairy products like milk, yoghurt, and cheese can interfere with the absorption of some antibiotics, such as ciprofloxacin and tetracycline. These should not be taken at the same time, and calcium supplements should be avoided for a few hours before and after the dose. The same precaution applies to certain osteoporosis drugs like alendronate (Fosamax).
His other specific warnings included:
- Avoid grapefruit if taking statins for high cholesterol.
- Avoid black liquorice with certain heart medicines like digoxin.
- Monitor banana intake with some ACE inhibitors for high blood pressure.
- Limit coffee with bronchodilators for asthma.
- Avoid smoked salmon and salami with some antidepressants.
- Avoid limes with certain cough medicines.
Dr Steele's overarching message was clear: "You should always ask your doctor about precautions you should take while being prescribed any new medication." He emphasised that avoiding certain foods or altering lifestyle habits might be necessary to prevent dangerous side effects and ensure treatments work as intended.
