Microbial changes in the gut may underlie broccoli’s anti-cancer properties
A new University of Illinois (U of I) study shows that microbial changes that occur in the human gut microbiome after eating broccoli might be behind the vegetable’s anti-cancer power.
Along with other health benefits, broccoli has been shown in research studies to play a role in slowing certain types of cancer. A new University of Illinois (U of I) study shows that microbial changes that occur in the human gut microbiome after eating broccoli might be behind the vegetable’s anti-cancer power.
“There is interest in broccoli and cancer because broccoli has been shown to slow cancer incidence in humans. This study gives us a better understanding of which microbes are creating the metabolites that have been shown to slow cancer in humans, so that we can do additional studies to see if the microbes that are increasing are part of this cancer-fighting mechanism,” explains Hannah Holscher, assistant professor of nutrition in the Dept. of Food Science and Human Nutrition at U of I and co-author of the study.
For the study, published in The Journal of Nutritional Biochemistry, healthy adults consumed a diet provided to them that included daily servings of broccoli and daikon radish for 18 days, and a control group that did not consume the broccoli/radish mix. Participants consumed cooked broccoli, but studies have shown that cooking broccoli can reduce the amount of glucosinolates and enzymes such as myrosinase, an enzyme related to releasing the cancer-fighting compounds from glucosinolates. Daikon radish was included with broccoli to mimic raw broccoli, by adding back the myrosinase.
Blood and fecal samples were taken on days 1 and 16 to look at bacterial changes in the microbiome. Of significant interest to the researchers was an increase in abundance of the Bacteroides genus, because some members of this bacterial genus have been shown to have myrosinase activities. “These bacteria have the enzymes to break down glucosinolates into cancer-fighting isothiocyanates, including sulforaphane.
“From this study, we believe some of the changes in blood metabolites are due to the microbiota because we saw changes about five hours after the broccoli was consumed. It’s more likely that those metabolites are from the microbes than just the digestive process of humans because of the timing: most nutrients are absorbed in the small intestine, within a couple of hours of ingestion. That was an interesting finding,” Holscher says.
Results also showed the presence of sulforaphane in the blood after five hours. Sulforaphane, a health-promoting food component found in cruciferous vegetables, particularly broccoli, is related to the prevention of prostate cancer and many other types of cancer. “What that suggests is that microbes are contributing to the creation of health-promoting food components that are beneficial for humans,” Holscher explains.
While the study doesn’t allow the researchers to make cancer-prevention health claims related to broccoli, it does provide a better understanding of how the microbes are changed. “And since other research has shown that broccoli can slow cancer, once we put those two outcomes together in a study, we can link those together,” Holscher says.