Before the procedure, not only should certain medications be discontinued . Supplements and herbal remedies may also increase the risk of intraoperative bleeding . According to findings by researchers at the Wroclaw Medical University, the list is quite long and often surprising .
Researchers from the Department of Dietetics and Bromatology and the Department of Pharmacognosy and Herbal Medicine at the Wroclaw Medical University examined the active substances contained in herbal preparations and dietary supplements in terms of their effect on blood clotting during surgical procedures .
“To date, only a few studies have examined the composition of specific preparations in the context of perioperative risks,” explains Dr. Joanna Pieczyńska, a professor at the Wroclaw Medical University, Department of Dietetics and Bromatology. “Our team decided to tackle the entire problem based on available publications. The results surprised us – we didn’t expect that so many commonly used preparations could pose a risk to patients during surgery. Physicians are often unaware of this. Few people ask patients before surgery whether they are taking dietary supplements containing garlic extract, birch bark, or other herbal preparations based on natural ingredients.”
If doctors don’t ask, patients often remain silent. Studies show that as many as 70% of patients do n’t inform their physicians about their use of dietary supplements or herbs. This is a huge gap in perioperative care. Many people believe that what’s natural is also safe, and that so-called “herbs” have never harmed anyone. The same applies to dietary supplements , primarily associated with preventative health support. However, their effects are not one-dimensional. They may be beneficial for one problem, but pose a risk in another.
“One such example is garlic,” says Dr. Joanna Pieczyńska. “Its beneficial health properties have been known for a long time. Garlic preparations are very popular, typically used to support blood pressure regulation and lipid profiles. Compounds contained in garlic inhibit platelet aggregation, so they should be discontinued at least a few days before surgery, as they increase the risk of bleeding. The same applies to cinnamon bark, which is an ingredient in many preparations that lower blood glucose and increase tissue sensitivity to insulin. For this reason, it is recommended for people with diabetes and insulin resistance, who, however , do not always know that they should stop taking it if they are undergoing surgery.”
The researchers examined herbal preparations and dietary supplements containing compounds with antithrombotic, antiaggregatory (inhibiting platelet clumping), or fibrinolytic (dissolving clots) properties. All of these can significantly affect blood clotting and increase the risk of perioperative bleeding. Potentially risky active substances include coumarins – found in sweet clot, cinnamon, and angelica. They may have antithrombotic effects as vitamin K antagonists. Another dangerous group of compounds in this context are salicylates – substances similar to acetylsalicylic acid (aspirin) that inhibit platelet aggregation. They are found, for example, in willow bark and aloe vera. The list of plants with fibrinolytic properties is long, including well-known and popular ones such as ginkgo biloba, ginseng, ginger, turmeric, garlic, St. John’s wort, and many others. They are also often used as spices and food additives, but Dr. Pieczyńska cautions that in this form they are harmless . The dose, the form of the preparation, and the bioavailability of the active substances are important. For example, herbal infusions contain significantly fewer active metabolites than standardized extracts – it’s difficult to overdose on cinnamon bark if you just add it to apple pie, but in concentrated form it can increase the risk of bleeding. The authors of the publication point out that when using multiple preparations simultaneously , the risk can accumulate, especially when combined with synthetic medications used before or after surgery.
“The problem is starting to be recognized worldwide,” says Dr. Joanna Pieczyńska. “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. This is for patient safety and the principle that prevention is better than risking uncontrolled bleeding. Meanwhile, in Poland, few people consult a pharmacist or other specialist before purchasing supplements . ”
This publication by the Wrocław -based authors is the first Polish-language study to systematize knowledge about plant ingredients that increase the risk of perioperative bleeding. It includes not only a list of substances and plants with this effect, but also a description of the mechanisms by which they affect blood clotting, as well as recommendations regarding the timing of withdrawal before surgery.
This is a practical tool for doctors, pharmacists and dietitians , but also an important signal for patients – before undergoing surgery, inform your doctor about all supplements and herbal preparations you are taking.
Pieczyńska JM, Grajeta H, Fecka I. The use of herbal medicines, herbal medical products , and dietary supplements before planned surgery. Part I. Ingredients of herbal medicines and dietary supplements increasing the risk of bleeding. Pharmacy Poland 2024; 80(1): 23–36.
DOI: 10.32383/farmpol/187177
photo: Tomasz Walów
