University Park, Pa.-- Ordinary rosemary -- the commonly used cooking
spice -- appears to help prevent breast cancer in laboratory rats, according
to a study in Penn State's College of Health and Human Development.
Rosemary interfered with cancer's initiation phase, or the transformation of normal cells to cancerous ones. The study, directed by John Milner, professor and head of the Department of Nutrition, is reported in the May issue of the Journal of Nutrition.
The results have "profound dietary implications," according to Milner. "We have found a spice that offers protection against a classic model of breast cancer," he says.
Rosemary significantly inhibited the binding of a known cancer-causing agent to the DNA in the rats' mammary cells. Scientists believe that that binding process is a necessary event in the formation of tumors.
The Penn State researchers fed the rats a diet supplemented with 1 percent rosemary for two weeks, using the same powdered rosemary readily available in grocery stores. They then treated the rats with DMBA, a chemical known to cause cancer. (DMBA has a structure similar to benzopyrenes, a class of carcinogens found in auto emissions and cigarette smoke.)
The rosemary diet reduced by 76 percent the number of instances of DMBA binding to the mammary cells, compared to rats fed a control diet.
In a separate experiment, the researchers fed rats a diet with half as much rosemary, then gave them half a dose of DMBA. The results were similar: DMBA's binding to mammary cells was reduced by 66 percent.
The researchers also found that rosemary's effectiveness against tumor formation increased with the amount of fat in the diet.
"It suggests that people who eat high-fat diets will actually get the most benefit from rosemary," Milner says. "For typical Americans, who eat more fat than they should, rosemary may be particularly important."
However, the type of fat consumed was important: Diets high in saturated fats seemed to block the protection that rosemary offered, while diets high in unsaturated fats were more beneficial.
Milner has already published a number of studies demonstrating the anti-cancer properties of another flavoring agent: garlic.
"We had worked with garlic and were curious if other compounds with antioxidant properties, such as the compounds in rosemary, would inhibit breast cancer," he explains.
The rosemary study was funded by the American Institute for Cancer Research and by Wakunaga of America, a food and pharmaceutical company.
Harunobu Amagase, a former research associate in Milner's laboratory, is the lead author on the Journal of Nutrition article. Other researchers on the study were research associate Kazuko Sakamoto, former undergraduate student Ellen Segal, and Milner.