As for most herbs, the mechanism of action of milk thistle remains in doubt. In mushroom poisoning and other liver-toxic exposure, silymarin is believed to get in the way of toxins trying to bind to liver cell membrane receptors by binding to the receptors itself. This is called competitive inhibition. Incidentally, glutathione, a compound that our body normally produces to protect the liver and kidney from reactive chemicals, works in a similar fashion. Many other suggestions of how milk thistle may function have been made, but which one is correct remains unclear.
Some evidence supports the idea that silymarin bound to phosphatidylcholine is better absorbed.
This form should be taken at a dosage of 100 to 200 mg twice daily. Safety Issues Milk thistle is believed to possess very little toxicity. Animal studies have not shown any negative effects even when high doses were administered over a long period of time. 13 A study of 2,637 participants reported in 1992 showed a low incidence of side effects, limited mainly to mild gastrointestinal disturbance. However, on rare occasions severe abdominal discomfort may occur.