A compound found in broccoli and related vegetables
may have more health-boosting tricks up its sleeves, according
to a new study led by researchers at the University of California,
Berkeley.
Veggie fans can already point to some cancer-fighting properties
of 3,3'-diindolylmethane (DIM), a chemical produced from the
compound indole-3-carbinol when Brassica vegetables such as
broccoli, cabbage and kale are chewed and digested. Animal studies
have shown that DIM can actually stop the growth of certain
cancer cells.
This new study in mice, published online (Monday, Aug. 20)
in the Journal of Nutritional Biochemistry, shows that DIM may
help boost the immune system as well.
"We provide clear evidence that DIM is effective in augmenting
the immune response for the mice in the study, and we know that
the immune system is important in defending the body against
infections of many kinds and cancer," said Leonard Bjeldanes,
UC Berkeley professor of toxicology and principal investigator
of the study. "This finding bodes well for DIM as a protective
agent against major human maladies."
Previous studies led by Bjeldanes and Gary Firestone, UC Berkeley
professor of molecular and cell biology, have shown that DIM
halts the division of breast cancer cells and inhibits testosterone,
the male hormone needed for growth of prostate cancer cells.
In the new study, the researchers found increased blood levels
of cytokines, proteins which help regulate the cells of the
immune system, in mice that had been fed solutions containing
doses of DIM at a concentration of 30 milligrams per kilogram.
Specifically, DIM led to a jump in levels of four types of cytokines:
interleukin 6, granulocyte colony-stimulating factor, interleukin
12 and interferon-gamma.
"As far as we know, this is the first report to show an immune
stimulating effect for DIM," said study lead author Ling Xue,
who was a Ph.D. student in Bjeldanes' lab at the time of the
study and is now a post-doctoral researcher in molecular and
cell biology at UC Berkeley.
In cell cultures, the researchers also found that, compared
with a control sample, a 10 micromolar dose of DIM doubled the
number of white blood cells, or lymphocytes, which help the
body fight infections by killing or engulfing pathogens. (A
large plateful of broccoli can yield a 5-10 micromolar dose
of DIM.)
When DIM was combined with other agents known to induce the
proliferation of lymphocytes, the effects were even greater
than any one agent acting alone, with a three- to sixfold increase
in the number of white blood cells in the culture.
"It is well-known that the immune system can seek out and destroy
tumor cells, and even prevent tumor growth," said Xue. "An important
type of T cell, called a T killer cell, can directly kill certain
tumor cells, virally infected cells and sometimes parasites.
This study provides strong evidence that could help explain
how DIM blocks tumor growth in animals."
DIM was also able to induce higher levels of reactive oxygen
species (ROS), substances which must be released by macrophages
in order to kill some types of bacteria as well as tumor cells.
The induction of ROS - three times that of a control culture
- after DIM was added to the cell culture signaled the activation
of macrophages, the researchers said.
