Sulforaphane, a compound found in broccoli and broccoli sprouts, has been found to kill the bacterium responsible for the majority of stomach cancers. The findings should lead to clinical trials to see whether eating vegetables containing the chemical can relieve infection, according to researchers from John Hopkins and the French National Scientific Research Centre.
In all but 15 to 20 per cent of cases, combinations of powerful antibiotics can kill helicobacter pylori, the bacterium recognised 20 years ago to be the cause of debilitating stomach ulcers and often fatal stomach cancers. Unfortunately, the regions of the world where the infection is most common are the same places where using antibiotics is most economically and logistically difficult.
"In some parts of Central and South America, Africa and Asia, as much as 80 per cent to 90 per cent of the population is infected with helicobacter, likely linked to poverty and conditions of poor sanitation," said study leader Jed Fahey, a plant physiologist in the Department of Pharmacology and Molecular Sciences at the Johns Hopkins School of Medicine.
"If future clinical studies show that a food can relieve or prevent diseases associated with this bacterium in people, it could have significant public health implications in the United States and around the world," he said.
In the experiments, the scientists discovered that purified sulforaphane even killed helicobacter that was resistant to commonly used antibiotics. They also proved that sulforaphane can kill the bacterium whether it is inside or outside cells. In people, cells lining the stomach can act as reservoirs of helicobacter, making it more difficult to get rid of the infection, said Fahey.
Even though the pure compound kills helicobacter efficiently, it remains to be seen whether dietary sources of sulforaphane (broccoli or broccoli sprouts, for instance) have similar effects. If so, vegetables native or adapted to various regions could be used by local populations to reduce helicobacter infection, noted Fahey, who has compiled a list of vegetables that contain sulforaphane or related compounds.
"We've known for some time that sulforaphane had modest antibiotic activity," said Fahey, who is also affiliated with the Center for Human Nutrition at the Johns Hopkins Bloomberg School of Public Health. "However, its potency against helicobacter, even those strains resistant to conventional antibiotics, was a pleasant surprise."
Sulforaphane was initially isolated from broccoli at Johns Hopkins because of its ability to protect cells against cancer by boosting their production of "phase 2" enzymes, a family of proteins that detoxify certain cancer-causing agents and damaging free radicals. However, the compound's antibiotic abilities are not well understood and are likely to occur through some other mechanism, claimed Fahey.
Sulforaphane can protect against chemically-induced stomach cancer in mice, the research team also found, but more studies are needed to know whether it can do the same against helicobacter-induced stomach cancer and whether dietary sulforaphane, rather than pure sulforaphane, will do the trick.
Fahey and The Johns Hopkins University own stock in Brassica Protection Products (BPP), a company whose mission is to develop chemoprotective food products and which sells broccoli sprouts.
The findings were reported in the 28 May issue of the Proceedings of the National Academy of Sciences.