Interaction: Shiitake Mushroom and Warfarin

Product

• preparation is called Lentinus edodes mycelium extract (LEM). 
• LEM is rich in polysaccharides and lignans

Rationale

• Taken both as vegetable and also exist in the form of supplementation
• is used for boosting the immune system, loweringbloodcholesterol levels, treating prostate cancer, and as an anti-aging agent.
•  Lentinan, derived from shiitake (Lentinus edodes), has been injected as an adjunct treatment for cancer and HIV infection, although currently high quality human scientific evidence is lacking for many proposed indications

Vitamin K Content

• Most mushroom (shiitake, white, Portabella, etc) has very small amount to no vitamin K
• Thus it does not cause reduction in INR

Blood Thinning Properties

• Several products containing mushroom extracts have not established any relationship with warfarin
• In a laboratory study, essential oil from shiitake inhibited platelet aggregation and therefore may increase the risk of bleeding 
•  Lentinan, the polysaccharide derivative of shiitake, may cause mildly abnormal blood cell counts (thrombocytopenia)
• Lentinus edodes has been shown to inhibit cyclooxygenase activity in laboratory study 
• Mushroom polysaccharides, especially beta-glucans such as lentinan from Lentinus edodes, may interfere with the way the liver breaks down certain drugs (through the suppression of CYP1As) (minor pathway in warfarin metabolism)

Recommendation

• Moderate intake vegetable should not cause much fluctuations in INR
• However, if taken in the form of supplementation consistently, may consider to review patient after a short period to assess changes in INR (expeced to increase slightly)

References

1. http://www.shopnaturesoasis.com/ns/DisplayMonograph.asp?storeID=0E75F5E3C2DF416C896EF03680134ECB&DocID=bottomline-shiitake
2. http://www.rxlist.com/maitake_mushroom-page3/supplements.htm
3. http://www.healthaliciousness.com/articles/low-vitamin-k-foods-for-a-coumadin-warfarin-diet.php
4. http://www.researchgate.net/profile/Prakash_Bisen/publication/44619902_Lentinus_edodes_a_macrofungus_with_pharmacological_activities/links/09e414ff4f0ceb5e9d000000.