Consuming a diet high in cruciferous vegetables is known to be associated with reduced cancer risk. Now, researchers find that daily consumption of broccoli sprouts inhibits the growth of Helicobacter pylori and reduces gastritis in patients infected with the bacteria, according to work presented at the AACR Frontiers in Cancer Prevention Research meeting.
Gastric cancer risk increases as much as six—fold in individuals infected with H. pylori. And though physicians sometimes use antibiotics to try to control the infection in patients, intracellular bacteria escape the effect of the drug. Also, drug—resistant strains are becoming more common, making multidrug combinations necessary to reduce the level of H. pylori colonization.
With these problems in mind, researchers have been working to find antimicrobial agents that are effective against both intracellular and extracellular bacteria.
One promising compound is sulforaphane, which is the major anti—cancer chemical found in broccoli. Sulforaphane kills H. pylori in vitro, even when the bacteria resides inside human epithelial cells.
More recently, Akinori Yanaka, MD, PhD, Assistant Professor at the Institute of Clinical Medicine at the University of Tsukuba in Japan, and colleagues found that feeding broccoli sprouts to mice infected with H. pylori reduced gastritis in the animals.
To find out if regular broccoli sprout consumption had a similar effect in humans, Dr. Yanaka's group enrolled 50 H. pylori—infected individuals into a clinical trial. Half of the participants were assigned to eat 100 grams of fresh broccoli sprouts each day for two months, and half were assigned to eat the same amount of alfalfa sprouts.
Alfalfa sprouts were chosen as the control food because they have a similar chemical composition to broccoli sprouts except they lack sulforaphane. (Broccoli sprouts were chosen over mature broccoli because the young plants have a higher concentration of sulforaphane.)
The researchers estimated the level of H. pylori colonization in each volunteer based on results from urea breath tests and measurements of H. pylori—specific stool antigen.
When measurements obtained at baseline were compared with those taken after one or two months of intervention, significant decreases in the amount of bacteria were evident in individuals eating broccoli sprouts, but not in those eating alfalfa sprouts. In no cases was the H. pylori infection completely eliminated, however.
The degree of gastritis was determined by measuring serum levels of pepsinogen, including the ratio of pepsinogen I to pepsinogen II. Again, there was an improvement in gastritis in the individuals eating broccoli sprouts, with overall decreases in both pepsinogen types and an increased ratio of pepsinogen I to II. No change was detected in the control arm.
All of the measurements returned to baseline within two months after the intervention was stopped.
“The results suggest these treatments may be useful for chemoprevention against gastric cancer,” said Dr. Yanaka. The team plans to test that hypothesis in a longer clinical trial in high—risk patients to determine whether consumption of broccoli sprouts can decrease the rate of either gastric cancer recurrence or progression from premalignant to malignant lesions.
Reductions are Significant
Commenting on the study, the Chair of the meeting, William G. Nelson, V, MD, PhD, Professor of Oncology at Johns Hopkins Medical Institutions, said that the H. pylori reductions caused by the isothiocyanates (sulforaphane) in the broccoli sprouts are significant and that the broccoli sprouts may have anti—inflammatory effects that may further reduce risks for gastric cancer.
“The upcoming trials may ascertain whether the broccoli sprouts can prevent stomach cancers,” Dr. Nelson said.
Broccoli Sprout Extract Decreases Skin Damage after UV—Exposure
Also reported at the AACR Cancer Prevention meeting, researchers from the Lewis B. and Dorothy Cullman Cancer Chemoprotection Center at Johns Hopkins School of Medicine found that topical application of broccoli sprout extract reduced cellular damage after ultra—violet light exposure in mice.
Hairless mice were exposed to UV light twice weekly for 20 weeks. After the exposure, the mice were divided into three groups, with one group treated topically with a concentrated sulforaphane extract (1.0 mmol); another treated with a low—dose extract (0.3 mmol); and a control group treated with acetone only, which was used as the solvent in all treatment arms. All groups were treated five times a week for 11 weeks.
After treatment, all of the animals in the control group had tumors, while only half of the animals in the high—concentration treatment group did.
Moreover, the tumor burden was halved in that arm compared with the control animals. The low—concentration extract also reduced the tumor burden, but all of the animals in that treatment arm developed tumors, suggesting that the higher—concentration extract was more effective than the less—concentrated one.
“We concluded from the study that broccoli sprout extract could be used as a treatment for skin cancer after exposure of UV light,” said Albena Dinkova—Kostova, PhD, who works in the laboratory of Paul Talalay, MD, and who presented the work at the meeting.
“Normally we think about eating broccoli but in this case the extract was applied topically, almost like a sunscreen, except it is blocking not the sunlight but its damaging actions,” said the Program Chair, William G. Nelson, V, MD, PhD, Professor of Oncology at Johns Hopkins Medical Institutions.
Dr. Dinkova—Kostova and colleagues now want to test whether feeding mice a diet rich in broccoli sprouts will have a similar protective effect. Interestingly, when Dr. Dinkova—Kostova was asked whether the full benefit of the food could be replicated in an extract, she said that previous in vitro work suggested that sulforaphane is the major active component.
“I do believe other components could have some synergistic effect and influence the absorption,” she said. “But, at least in our animal studies, we can attribute everything to sulforaphane in terms of induction of Phase II enzymes,” which are the protective anti—oxidant enzymes triggered by broccoli sprouts and other cruciferous vegetables.