Eat your broccoli! It’s a plea made every night at dinner tables across the country. And it’s a plea worth listening to, because broccoli and other cruciferous vegetables—such as kale, cabbage, and cauliflower—are a rich source of healthful nutrients .
But the reasons that these veggies are good for us turn out to be more complicated (and more interesting) than people thought in the past. Whether your body can take full advantage of the health benefits of these veggies may, in fact, depend on the microbes (bacteria) living in your gut.
Elizabeth Sattely, winner of a 2013 NIH Director’s New Innovator Award and a chemical engineering professor at Stanford University in California, is now busy learning more about how our bodies process the nutrients in the vegetables we consume. In particular, she wants to identify the species of microbes responsible for transforming each type of plant nutrient into beneficial health-promoting molecules, and then trace the chemical reactions involved.
Sattely’s primary area of study is the special molecules found in plants, including a group of sulfur-containing metabolites, known as glucosinolates, that give broccoli, cauliflower, and Brussels sprouts their distinctive aroma and taste. But that’s just part of the story. During digestion, glucosinolates are broken down and transformed by microbes into biologically active compounds, such as indoles, nitriles, thiocyanates, and isothiocyanates. These compounds, which can provide benefit by reducing inflammation, have been found to inhibit bladder, breast, colon, liver, lung, and stomach cancers in animal models. In addition, experiments with animals and cells grown in the lab have shown that these compounds protect DNA from damage, inactivate carcinogens, and trigger the death of sick cells. But you need your microbes to make that possible.
Sattely also suspects that some people may benefit more than others. Why on earth would she think this? Well, we do know that the community of microbes—the so-called “microbiome”—in the gut varies among different people. And that has led Sattely to hypothesize that some individuals’ intestines may not contain enough of certain key species of microbes to carry out the chemical reactions needed to produce optimal levels of plant-derived nutrients.
In her project, Sattely plans to test a panel of common gut bacteria in the lab to see if they activate the health-promoting properties of the natural chemicals found in various vegetables. To do this, she will cultivate each bacterial species in the presence of plant-derived nutrients and then use an analytical chemistry technique called high-performance liquid chromatography (HPLC) mass spectrometry to determine if the bacterium has chemically transformed the plant-derived nutrient. After identifying the critical microbial species, she will use animal models to test how each species unlocks dietary plant nutrients.
Figuring out which microbes are key to generating nutrients that lower the risk of disease could help us identify individuals who may benefit from more of these microbes. If that pans out, a preventive care visit to the doctor might someday include a prescription for an extra dose of microbes, along with recommendations on diet and exercise.
Sattely even envisions the day when certain foods, such as yogurt, might be precisely engineered to contain certain communities of microbes—each tailored to helping a particular individual reap the most health rewards from a particular diet. Just imagine a future in which drinking a yogurt smoothie could help you get the biggest bang out of your dinner veggies!
 Anticarcinogenic activities of sulforaphane and structurally related synthetic norbornyl isothiocyanates. Zhang Y, Kensler TW, Cho CG, Posner GH, Talalay P. Proc Natl Acad Sci U S A. 1994 Apr 12;91(8):3147-50.
Elizabeth Sattely, Stanford University, Project Title: Liberation of Plant Nutrients by the Gut Microbiota
Cruciferous Vegetables and Cancer Prevention. (NIH/National Cancer Institute fact sheet)
Dietary Guidelines for Americans. (USDA)
NIH support: Common Fund