Broccoli Sprouts May Protect Against Gastric Cancer

Roxanne Nelson

April 08, 2009

April 8, 2009 — Preliminary research suggests that broccoli sprouts have chemopreventive properties. In a pilot clinical trial and an animal study, researchers found that the consumption of broccoli sprouts can reduce colonization of Helicobacter pylori, which is associated with the development of gastritis and gastric cancer. In addition, consuming broccoli sprouts appears to enhance antioxidant and anti-inflammatory enzymes in the stomach.

The study, published in the April issue of Cancer Prevention Research, builds on earlier research about the potential value of sulforaphane, a naturally occurring biochemical that is found in relative abundance in fresh broccoli sprouts. Laboratory experiments using purified sulforaphane have shown that it displays antibacterial properties against helicobacter and even kills strains that are resistant to commonly used antibiotics (Proc Natl Acad Sci U S A. 2002;99:7610-7615).

"In our 2002 study, sulforaphane killed helicobacter directly in the test tube," said study author Jed W. Fahey, MS, ScD, a nutritional biochemist in the Lewis B. and Dorothy Cullman Cancer Chemoprotection Center at the Johns Hopkins University School of Medicine, in Baltimore, Maryland. "It also reduced the rate of gastric cancer in mice."

Although the pure compound effectively eliminated helicobacter, it was not clear whether the same effect could be reproduced with dietary sources of sulforaphane. The current study showed that a dietary source might to exert a similar but milder effect.

We're now giving people the science that shows why eating fruits and vegetables is good for your health.

"The key take-home message harkens back to the old message — eat veggies," Dr. Fahey told Medscape Oncology. "We're now giving people the science that shows why eating fruits and vegetables is good for your health."

Research has shown that fruits and vegetables contain phytonutrients, which might have a protective effect. "Right now," said Dr. Fahey, "we're providing the evidence that shows that broccoli is good for you."

The current research is actually 2 complementary studies — 1 in mice and 1 in humans infected with H. pylori — in which sulforaphane-rich broccoli sprouts were added to the diet.

Reduction Seen in Biomarkers of Inflammation and H. pylori Colonization

The human trial was conducted in Japan, where there is a high incidence of chronic H. pylori infection. A cohort of 48 people with H. pylori infection were randomized to consume either 70 g/day of broccoli sprouts (containing 420 μmol of sulforaphane precursor) for 8 weeks, or an equal amount of alfalfa sprouts. Although rich in phytochemicals, alfalfa sprouts do not contain sulforaphane.

All study participants had blood, stool, and urine samples collected on days 0, 28, 56, and 112. In stool samples, H. pylori stool antigen (HpSA), which is a biomarker of H. pylori colonization, was analyzed, and in blood samples, serum pepsinogens (PG)I and PGII, biomarkers of gastric inflammation, were measured. The severity of current H. pylori colonization was assessed using the urea breath test.

The researchers found that the level of HpSA was reduced by more than 40% in the broccoli-sprout group but was unchanged in the alfalfa group. During the intervention period, there were also significant reductions in both PGI and PGII (P < .05), but only in the broccoli-sprout group.

However, values for HpSA and PGI/II returned to baseline levels 2 months after the intervention. Broccoli-sprout consumption does reduce H. pylori colonization, the researchers note, but does not completely eradicate the pathogen.

Data From Experimental Model

In the first experiment of the mouse trial, C57BL/6 female mice infected with H. pylori Sydney strain 1 were maintained on a high-salt diet (7.5% NaCl) and were fed broccoli sprouts. The result was reduced gastric bacterial colonization and attenuated mucosal expression of tumor necrosis factor-α and interleukin-1β, which are major proinflammatory cytokines that are elevated in gastric mucosa by H. pylori infection. Broccoli sprouts added to the diet suppressed the upregulation of these cytokines.

They also observed that the protective effect against gastric mucosa inflammation was paralleled by significant inhibition of gastric atrophy and reduced levels of both 8-OHdG and single-stranded DNA, which are markers of apoptosis.

A second experiment was conducted using H. pylori–infected mice that had been genetically engineered to lack the Nrf2 gene, which activates protective enzymes. Consumption of broccoli sprouts did not appear to offer the same protection to this group of mice. This finding confirmed previous findings that Nrf2 plays a role in protecting against H. pylori–induced inflammation and gastritis, according to the researchers.

Possible Reduction of Cancer

"In our study, we reduced levels of H. pylori," said Dr. Fahey. "Reducing the risk of stomach cancer was not the outcome, but the progression is clear — the risk of cancer is 3- to 6-fold higher with H. pylori infection."

"If you reduce colonization, then you can reduce infection," he added. "We didn't cure anyone, but we never expected dietary intervention alone to do that."

As the population ages, the incidence of cancer is expected to increase. "The number of new cases will double in the next 25 years, so the burden on the health system will be intolerable," said Paul Talalay, MD, the John Jacob Abel Distinguished Service Professor of Pharmacology and director of the Laboratory for Molecular Sciences at Johns Hopkins University School of Medicine.

"It is not a choice to look at prevention or protection against cancer, it is a mandate," said Dr. Talalay in a statement.

It is not a choice to look at prevention or protection against cancer, it is a mandate.

Although not involved in this study, Dr. Talalay is a pioneer in the study of dietary phytochemicals that might help protect against cancer, and he is scheduled to receive the Linus Pauling Institute Prize for Health Research on May 18, 2009. The award is one of the leading honors in the world for scientists studying micronutrients, diet, and other natural approaches to disease prevention or therapy.

The study was supported by the Ministry of Education, Culture, Sports, Science and Technology, Japan; the Lewis B. and Dorothy Cullman Foundation; and the American Institute for Cancer Research. Dr. Fahey is a cofounder of Brassica Protection Products LLC, a company that is licensed by Johns Hopkins University to produce broccoli sprouts. Dr. Fahey's coauthors have disclosed no relevant financial relationships.

Cancer Prev Res (Phila Pa). 2009;2:353-360. Abstract

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