Broccoli sprouts 'cut gut infection'

Monday April 6 2009

“Eating a daily portion of broccoli sprouts could help tame the H. pylori bacteria, linked to stomach ulcers and even cancer,” BBC News reported. It said that research in 50 people in Japan found eating broccoli sprouts might give some protection. The news service continued that UK experts said while the vegetable may have an effect on levels of the bacteria, it probably made no difference to the risk of cancer.

This research involved both mice and humans infected with Helicobacter pylori and fed a diet of broccoli sprouts, which contain high levels of the compound sulforaphane (SF). Previous research has demonstrated that SF kills the H. pylori bacteria and enhances antioxidant and anti-inflammatory enzymes. This research found that mice fed broccoli sprouts had reduced stomach inflammation. In a trial in humans, a diet of SF-rich broccoli sprouts also reduced H. pylori levels.

The findings are promising but more research is needed to determine the possible implications for human illness, particularly cancer. At present, H. pylori infection is effectively treated with a combination of antibiotics and stomach acid-reducing treatments.

Where did the story come from?

Akinori Yanaka and colleagues from Tokyo University of Science, Japan, carried out this research. The study was funded by the Ministry of Education, Culture, Sports, Science and Technology in Japan, the Lewis B and Dorothy Cullman Foundation (New York, NY), and the American Institute for Cancer Research (Washington, DC). The study was published in the peer-reviewed medical journal: Cancer Research Prevention.

What kind of scientific study was this?

The researchers say that the Helicobacter pylori bacteria is associated with the development of stomach ulcers and stomach cancer. They say that research shows certain chemical compounds, such as salt, amines from burned fish, and nitroso (made in the stomach) may accelerate the development of stomach cancer.

Meanwhile, many vegetables and fruits are believed to have anti-cancer properties although it is uncertain why. Cruciferous vegetables, in particular broccoli, have been of particular interest for the possible anti-cancer properties of certain compounds they contain, such as isothiocyanate sulforaphane (SF). SF has bactericidal (bacteria killing) effects against H. pylori , and has demonstrated to prevent chemically induced stomach tumours in mice. Broccoli sprouts are rich in SF.

This research examined the effects of SF on genetically engineered mice infected with H. pylori and given a high salt diet (known to increase H. pylori growth in mice). It also looked at the effects of feeding broccoli sprouts or the ‘placebo’ alfalfa sprouts (that do not contain SF) to 48 human patients infected with H. pylori .

SF encourages the body to produce protective enzymes that have antioxidant and anti-inflammatory properties in cells. It does this through Nrf2 (a transcription factor involved in the transfer of genetic information from DNA and the production of enzymes). The researchers infected two groups of six-week-old female mice with H. pylori . One group consisted of normal mice and the other contained mice genetically engineered to lack the transcription factor Nrf2.

Once the mice had tested positive for H. pylori , they were given a high-salt diet for two months. Both groups of mice were then each split again into two groups, with two of the subgroups given plain water and the other two given water with a mix of blended broccoli sprouts with high amounts of SF. After eight weeks, the researchers analysed the effects on the mouse stomach lining in the laboratory.

The human patients that were infected with H. pylori received eight weeks treatment with either the alfalfa sprouts or 70g/day of SF-rich broccoli sprouts. All the patients visited the hospital for collection of blood, stool samples (for measurement of H. pylori), and urine samples (for measurement of a breakdown product of SF) at days 0, 28, 56, and 112. Severity of current H. pylori colonisation was assessed by the urea breath test, a routine clinical test for H. pylori .

What were the results of the study?

Giving SF-rich broccoli sprouts to normal female mice infected with H. pylori and fed on a high-salt diet reduced stomach bacterial colonisation. The diet was also found to reduce expression of inflammatory markers (tumour necrosis factor-α and interleukin-1β) in the stomach mucosa and reduced stomach inflammation. It also prevented atrophy (wasting) of the stomach caused by the high-salt diet. In mice who were genetically engineered to lack the nrf2 gene (and so who were not able to produce the transcription factor that allows SF to exert its effects in producing protective enzymes), these effects were not seen. The researchers say this strongly implies that Nrf2 and SF-are involved in the production of antioxidant and anti-inflammatory proteins.

Compared to patients given a placebo, those people given broccoli sprouts had decreased levels of urease (measured by the urea breath test) and also had reduced H. pylori in the stool antigen, demonstrating a reduced H. pylori colonisation. Markers of stomach inflammation (taken from stomach samples) were also reduced.

What interpretations did the researchers draw from these results?

The researchers concluded that daily intake of SF-rich broccoli sprouts for two months reduces H. pylori colonisation in mice and improves the outcome of infection in both mice and humans. They say the treatment seems to enhance cancer protection of the stomach mucosa against H. pylori –induced oxidative stress.

What does the NHS Knowledge Service make of this study?

This research involved both mice and humans that had been infected with H. pylori and fed a diet of SF-rich broccoli sprouts. It demonstrated that SF appeared to reduced stomach inflammation and H. pylori levels. It is not known whether this was due to SF-induced inhibition of H. pylori colonisation (its bacteria-killing effects), or to increased Nrf2-dependent anti-inflammatory and antioxidant enzyme activity or by some combination of these two modes of protection.

These promising findings are from a randomised trial, which increases the confidence in the results. However, it involved only small numbers of patients and more research is needed to reveal the possible implications for human health. Studies that assess the clinical impact on humans, such as the incidence of stomach ulcers or cancer, will be important. At present, H. pylori infection is effectively treated with a combination of antibiotics and stomach-acid-reducing treatments.

Analysis by Bazian
Edited by NHS Choices