Milk Thistle

Clarifying milk thistle nomenclature

It’s easy to fall into the trap of using names incorrectly, assuming that differences are unimportant.

Milk thistle extracts are being studied to treat cancer and lessen the side effects of chemotherapy. Here’s what we should know, terminology-wise.

Milk thistle extract

  • The initial extract of crushed milk thistle seeds
  • Contains 65% to 80% silymarin and 20% to 35% fatty acids, such as linoleic acid


  • The most common class of compounds in milk thistle extract


  • A purified version of milk thistle extract
  • Contains at least 7 flavonolignans and 1 flavonoid that comprises 65% to 80% of milk thistle extract


  • A semipurified, commercially available form of silymarin
  • A roughly 1:1 mixture of silybin A and silybin B


  • Similar but more potent than silibinin, and may be produced more economically

Probably more than we need to know right now, but later it might be important.

7/16/07 18:32 JR

Hi, I’m JR

John Russo, Jr., PharmD, is president of The MedCom Resource, Inc. Previously, he was senior vice president of medical communications at, a complementary and alternative medicine website.