For years, scientists who theorized that women could avoid breast cancer by eating foods packed with certain chemical compounds were regarded as renegades.
Now some of those theories are producing intriguing results, and some scientists have trained a spotlight on a family of kissing cousins -- cruciferous vegetables, including cabbage, cauliflower, collard greens and, most of all, broccoli.
"A variety of healthy foods can provide a broad range of protective compounds," said Karen Collins, nutrition consultant for the American Institute for Cancer Research, a charity that supports research on diet and cancer prevention. "We are only beginning to scratch the surface into what they may involve."
Even as food science and medical research increasingly intersect, many doctors are cautious about sweeping recommendations that focus on a single family of plant foods. Research into foods that combat breast cancer faces a powerful institutional barrier: money. Consumer advocates note that conducting studies that follow people for years to see they do not get sick as they eat certain foods is expensive. By comparison, drug approval is more efficient.
"The world is still not ready for prevention as a way to handle the medical problems of an aging population," said Dr. Paul Talalay of Johns Hopkins University, the leader on research that suggests the cancer-thwarting potential of broccoli.
Still, the menu of possible cancer-fighting foods is growing. Collins said there was also evidence compounds from an array of foods may work together. Walnuts recently have been found to possess a powerful effect against breast cancer cells because they contain a type of omega-3 fatty acid (alpha-linolenic acid -- ALA) that reduces inflammation, prevalent in a variety of medical conditions, including cancer. Canola oil and flaxseed are additional ALA sources, she said.
New research also has pointed to pigment compounds in strawberries, pomegranates and green tea as providing protection against breast cancer.
Talalay was the first to isolate a broccoli-related compound called sulforaphane glucosinolate in 1992, which shows potent activity against breast cancer cells. Other scientists, such as Dr. Jerry Kosmeder of the University of Chicago, also have demonstrated that sulforaphane may be a powerful anti-cancer agent.
Researchers say the compound energizes enzymes in the body that inhibit cells from becoming cancerous. Sulforaphane is present in all cruciferous vegetables but is most abundant in broccoli.
The compound can also enhance the activity of two key enzymes in the body that fight against tumor development. "We found that cruciferous vegetables were very effective in boosting these enzymes and it now appears to be associated with their unique chemistry," Talalay said.
In a Talalay study, lab mice dosed with sulforaphane never developed cancer. However, rodents fed their usual diet developed debilitating cancers.
Talalay has found the highest concentration of sulforaphane is in broccoli sprouts, which contain about 20-50 times more than mature plants. Working with a plant physiologist at Johns Hopkins, Talalay's team has developed a seed that produces sprouts with exceptional sulforaphane levels. He and his university team sell the seeds to a network of growers who grow them into sprouts for sale in supermarkets.
Yet, after nearly 20 years, Talalay has not conducted a large-scale clinical trial that could produce the kind of evidence needed to win sulforaphane's official endorsement from the medical community.
Prevention trials, he said, are difficult to conduct because they require thousands of people who would have to be monitored over 20 years. The cost of managing such a trial, he added, would be too high.
Arthur Levin, director of the Center for Medical Consumers in Manhattan, is not surprised. In a prevention trial based on a vegetable chemical, he noted, the aim is to show a disease did not occur, a concept often difficult to prove, whereas, with drugs, the aim is to prove the treatment of an existing disease.
"If they have to run a trial for 15 or 20 years that means they're not going to see any return on their investment for a very long time," said Levin, who has served on numerous advisory committees of the Food and Drug Administration, which oversees the approval of pharmaceuticals.
From the October 13, 2008, Prepared Foods e-Flash