Milk Thistle May Slow Lung Cancer

June 20, 2006 -- A compound from the milk thistle plant might slow the progression of lung cancerlung cancer, according to lab tests done on mice.

The compound, called silibinin, hasn't been studied for lung cancercancer in humans yet. So the researchers -- who included Rana Singh, PhD, of the University of Colorado's School of Pharmacy -- aren't making any recommendations for people.

Lung cancer is the world's leading cause of cancer deaths. Singh's team tested silibinin to see if it could curb lung cancer in mice.

Why study silibinin? It has shown promise against other types of tumors in tests on rodents, and has few side effects, the researchers note. Their study appears in the Journal of the National Cancer Institute.

Milk thistle is a plant native to the Mediterranean area. It's been used for thousands of years for various ailments, especially liver problems, states the web site of the National Center of Complementary and Alternative Medicine (NCCAM), part of the National Institutes of Health.

Milk thistle is sold in the U.S. as a dietary supplement. It's sometimes called silymarin, which is a mix of milk thistle's active components, including silibinin, notes the NCCAM.

Mouse Study

Singh and colleagues injected 90 young, male mice with a chemical that causes lung cancer. Two weeks later, they added various doses of silibinin to food for most of the mice.

For comparison, the scientists didn't give any silibinin to a small group of mice.

After the mice had been on those diets for 4.5 months, the researchers checked on the mice's lung cancer. They found smaller lung tumors in the mice with silibinin in their diets, compared with those consuming no silibinin. They also had fewer large lung tumors.

Nine weeks later, that pattern still held. What's more, the silibinin group showed fewer new blood vessels in their lung tumors and lower levels of cancer-promoting chemicals.

The study shows no side effects with any of the silibinin doses tested on the mice.

How Did It Work?

Silibinin appeared to put the brakes on lung cancerlung cancer's growth and spread. But it didn't seem to spur cancercancer cell death, the study shows.

Singh's team isn't sure exactly how silibinin affected the mice's lung cancer.

"Although the mechanisms by which silibinin interferes with lung tumor growth in preclinical models remain to be explored, these results raise the possibility that silibinin may have chemopreventive activity against lung tumor growth and progression in humans," the researchers write.

They call for further studies of silibinin and lung cancer.

More on Milk Thistle

The NCCAM -- which wasn't involved in Singh's study -- provides this background information on milk thistle:

• Few side effects have been reported for milk thistle, though there have been occasional reports of a laxative effect, upset stomach, diarrheadiarrhea, and bloating.
• Milk thistle may also trigger allergic reactions, especially in people who are allergic to plants in the same family (such as ragweed, chrysanthemum, marigold, and daisy).
• Little is known about milk thistle's interactions with anticancer medications or other drugs, states the NCCAM.

Dietary supplements aren't regulated like prescription drugs in the U.S. That is, they haven't been evaluated by the government for safety and efficacy.

The NCCAM advises people to tell their doctors about any dietary supplements they take. "This helps to ensure safe and coordinated care," states the NCCAM's web site.

SOURCES: Singh, R. Journal of the National Cancer Institute, June 21, 2006; vol 98: pp 846-855. News release, Journal of the National Cancer Institute. National Center for Complementary and Alternative Medicine: "Herbs at a Glance: Milk Thistle." National Center for Complementary and Alternative Medicine: "Milk Thistle (PDQ) Health Professional Version."