The herb, used for as long as 2,000 years to battle a variety of ailments, may help protect against liver damage from chemotherapy, researchers say in Cancer, the journal of the American Cancer Society.
Previous studies have looked into whether milk thistle could be used to treat liver damage from hepatitis and cirrhosis, the researchers note.
Elena Ladas, MS, RD, of Columbia University Medical Center and colleagues set out to test whether milk thistle could help treat people with chemotherapy associated liver problems.
They conducted a study in children with acute lymphoblastic leukemia (ALL) with liver toxicity related to chemotherapy. The researchers enrolled 50 children, and participants were randomly assigned to receive either milk thistle or placebo for 28 days.
All children at the start of the study had evidence of liver inflammation as measured by elevations in blood levels of the liver enzymes aspartate amino transferase (AST) and amino alanine transferase (ALT).
The researchers measured liver enzymes on all the children at day 56, which was 28 days after receiving either milk thistle herb or the placebo. Children who had received milk thistle had improvements in their liver enzymes compared with the children in the placebo group.
The youths who took milk thistle had significantly lower levels of AST and a trend toward significant lower levels of ALT, the researchers say.
Milk thistle also seemed to help keep fewer patients from having to lower the dose of their chemotherapy drugs.
Chemotherapy doses were reduced in 61% of those on milk thistle, compared to 72% in the placebo group. Milk thistle appeared to be safe for consumption, the researchers write.
"Milk thistle needs to be studied further to see how effective it is for a longer course of treatment and whether it works well in reducing liver inflammation in other types of cancers and with other types of chemotherapy," says co-researcher Kara Kelly, MD, of New York-Presbyterian Hospital.
The researchers write that scientists have begun to understand more about the workings of milk thistle in the past two decades. It is available in the U.S. as a dietary supplement but most often is used for its effects on the liver.
"This is the first randomized, controlled clinical study to investigate the feasibility and safety of the herbal plant milk thistle," the researchers write, "in combination with the administration of chemotherapy in children undergoing treatment for cancer."