Our mothers told us to eat our vegetables: Now we know why
A compound in broccoli and other cruciferous vegetables may be able to not only help prevent cancer but also help to treat it—a new approach researchers at Texas A&M Health Science Center are calling “from the table to the bedside.” Although no one is suggesting giving up traditional chemotherapy and radiation treatments for cancer, compounds from food may actually help cancer drugs work more effectively.
This cancer-fighting compound is called sulforaphane, and it is found in vegetables like Brussels sprouts, kale, cauliflower and cabbage, but its highest concentrations are in the young sprouts of broccoli. Sulforaphane can also be found in a dietary supplement called broccoli sprout extract, or BSE.
Researchers at the Texas A&M Health Science Center Institute of Biosciences and Technology (IBT) in Houston, along with collaborators in Oregon, had previously found that sulforaphane could inhibit colon and prostate cancer cells in the laboratory. They’ve now shown that it seems to help humans as well.
Roderick H. Dashwood, professor and director of the Center for Epigenetics & Disease Prevention at the Texas A&M IBT, takes a “field-to-clinic” approach to cancer prevention. He and a collaborator, Praveen Rajendran, Ph.D., assistant professor at the center, published a new study in the journal Clinical Epigenetics that indicates a BSE supplement may help prevent or even treat colon cancer and hints at the biological pathways involved.
The BSE supplement seems to be generally safe. “We have not seen any serious adverse events in healthy volunteers who consumed BSE pills for seven days,” Rajendran said, although some people did experience mild abdominal discomfort. He cautions, however, that not all broccoli supplements are necessarily as effective as the one tested. “We have used a standardized broccoli extract in our study provided by Johns Hopkins University,” Rajendran said. “This BSE supplement is being evaluated in several other clinical trials around the country, but I’m not sure other, similar supplements available to the public have the same level of active ingredients, including sulforaphane.”
In a separate clinical study, 28 human volunteers over the age of 50, who were undergoing routine colonoscopies, were surveyed for their cruciferous vegetable-eating habits. When their colon biopsies were examined, those who ate more servings were found to have higher levels of expression of the tumor suppressor gene p16 than those who ate few or no cruciferous vegetables. This effect on p16 held even for people who didn’t eat these vegetables every single day, which may seem strange, as a single serving of sulforaphane is generally cleared from the body in less than 24 hours. “This hints at the possibility that epigenetic mechanisms are initially triggered by sulforaphane and its metabolites, and downstream mechanisms could be sustained, at least in the short-term, even after compounds are eliminated from the body.” In other words, eating vegetables containing sulforaphane can actually change your genes to make your body better able to prevent tumor growth.
However, it’s not all good news. In animal models, sulforaphane was shown to generally inhibit the development of colon cancer, but it’s a bit of a two-edged sword. Sulforaphane induces a protein called Nrf2, which has beneficial antioxidant and detoxifying effects—and is obviously good for fighting cancer. Later in the development of cancer, though, Nrf2 can also have a role in tumor growth and can even enhance the buildup of plaque in the arteries. “Because of all this, we believe that Nrf2 status is worthy of further investigation,” Rajendran said, “not just for cancer treatment but for its role in modulating cardiovascular disease.”
“Our work provides comprehensive proof-of-principle using cell-based, animal and human studies that dietary compounds like sulforaphane can be chemopreventive,” or able to help prevent cancer, Rajendran said. “However, we’re not quite ready to recommend everyone take a BSE supplement, and it’s certainly worth reiterating what nutritionists have said for years: eat your vegetables.”