Patients should stop not only certain medications but also supplements and herbal preparations before surgery, as many can increase the risk of intraoperative bleeding, researchers at Wrocław Medical University have found.
The study, conducted by the Department of Dietetics and Bromatology and the Department of Pharmacognosy and Herbal Medicine, examined active substances in supplements and herbs that affect blood clotting during surgical procedures.
“The results are surprising because so many commonly used preparations can be dangerous to patients during surgery,” said Joanna Pieczyńska, PhD, quoted in a university press release.
She added that the problem is underestimated, saying: “Doctors often lack this awareness as well. Few ask patients before surgery whether they are taking dietary supplements containing garlic extract, birch bark, or other herbal preparations based on natural ingredients.
“Research,” she continued, "shows that as many as 70% of patients do not inform their physicians about their use of dietary supplements or herbs. This is a huge gap in perioperative care.”
Noting that many patients assume natural products are safe, Pieczyńska said: “One such example is garlic. Its beneficial health properties have long been known. Garlic preparations are very popular, typically used to support blood pressure regulation and lipid profiles.
“Compounds in garlic inhibit platelet aggregation, so they should be discontinued at least a few days before surgery because they increase the risk of bleeding.”
The same applies to cinnamon bark, widely used in supplements for blood glucose control. While recommended for people with diabetes or insulin resistance, it should also be stopped before surgery.
Researchers listed several groups of compounds with anticoagulant effects: Coumarins, found in sweet clover, cinnamon, and angelica, act as vitamin K antagonists; Salicylates, similar to aspirin, are present in willow bark and aloe vera; Plants with fibrinolytic properties include ginkgo biloba, ginseng, ginger, turmeric, garlic, and St. John’s wort.
These substances are safe in culinary amounts but can be risky in concentrated supplement form. Multiple preparations taken together can intensify the effects, especially when combined with prescription drugs.
Pieczyńska said: “The problem is already beginning to be recognized worldwide. For example, the American Society of Anesthesiologists recommends discontinuing supplements and herbal products at least two weeks before a planned procedure — even if their exact mechanisms of action are unknown.
“The key is patient safety and the principle that prevention is better than risking uncontrolled bleeding. Meanwhile, in Poland, few people consult a pharmacist or another specialist when purchasing supplements.”
According to the university, the study is the first Polish-language publication to systematize knowledge about herbal ingredients that increase perioperative bleeding risk. It includes a list of plants, descriptions of their mechanisms, and withdrawal guidelines.
“This is a practical tool for doctors, pharmacists, and dietitians, but also an important reminder for patients: before undergoing surgery, inform your doctor about all supplements and herbal preparations you are taking,” the press release said. (PAP)
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