Which herbal supplement is least likely to increase the risk of perioperative bleeding?

St. John's wort is the herbal supplement least likely to increase the risk of perioperative bleeding due to its primary action as an antidepressant and its influence on neurotransmitter systems rather than on blood coagulation. Unlike the other options, St. John's wort does not have a significant impact on platelet function or blood thinning properties.

Garlic and ginkgo biloba are both known to possess properties that can affect platelet aggregation and may enhance bleeding risk. Garlic has natural anticoagulant effects, which can interfere with blood clotting mechanisms. Similarly, ginkgo biloba is recognized for its ability to affect blood flow and may inhibit platelet activating factors, increasing the likelihood of bleeding during surgery.

Saw palmetto, while often used for urinary tract health, has been associated with some potential for anticoagulation, albeit less strongly than garlic or ginkgo. However, it has not been shown to have as direct an effect on bleeding risk as those two.

In summary, St. John's wort stands out for its lack of connection to perioperative bleeding risk, making it the safest choice among these supplements when considering their potential effects on surgical outcomes.