URBANA, Ill. — Love it or hate it, broccoli is chock-full of health-promoting chemicals linked to heart health, cancer prevention, immune function, weight management, and more. However,  some people are less efficient than others at unlocking those chemical benefits. A research team at the University of Illinois Urbana-Champaign suggests gut microbe communities may be responsible for the variation. With a new grant from the USDA’s National Institute of Food and Agriculture, the team plans to identify which microbes maximize the benefits of broccoli and other brassica vegetables. 

Gut microbes only factor in when we eat cooked broccoli. When eating the vegetable raw, healthy compounds — and a bitter taste — are unleashed with every gnash of our teeth, the result of a chemical reaction activated by physical damage. Eliminating the bitterness is easy; we just have to cook it. But cooking inactivates the enzyme involved in the reaction, myrosinase. Thankfully, some microbes manufacture their own version of myrosinase, making it possible for them to complete the reaction in the gut with varying levels of efficiency. 

“Gut bacteria can metabolize glucosinolates in broccoli to isothiocyanates (ITCs), the bioactive compounds with known health benefits, but they can also break glucosinolates into other inactive materials that do nothing for us. We’re focusing on the flux between these metabolic outcomes and how we can potentially steer that flux towards ITCs and away from the non-bioactive products,” said Michael Miller, principal investigator of the grant and professor in the Department of Food Science and Human Nutrition, part of the College of Agricultural, Consumer and Environmental Sciences (ACES) at U. of I.

The first step is identifying which bacteria are involved and how efficiently they produce ITCs versus non-beneficial compounds. Miller’s team has a study underway in mice, a model system that can provide clues for future human studies. He is feeding the mice broccoli and kale, both cooked and uncooked, to understand the chemical and microbial dynamics of the system. 

Once ITCs are unlocked — whether in the mouth or the gut — they trigger bitter-taste receptors in cell membranes, starting a series of reactions that produce hormones affecting glucose homeostasis and the perception of fullness.

“We actually have bitter taste receptors all the way down, not just in our mouths, but in our colon and small intestine, too,” Miller said. “The goal of our work is to show that the bitter compounds (ITCs) made by gut bacteria from metabolizing broccoli trigger bitter taste receptors in the gut and impact satiety, causing mice to eat less.”

Once he identifies bacterial superstars that maximize ITC production for anti-cancer and weight management benefits, Miller says custom probiotics could be developed to help level the playing field for people with lower-efficiency microbial communities. He also predicts his research will inform recommendations about whether raw or cooked broccoli (or kale) might be more useful for weight loss.