When we eat a food product, we don’t typically think about the byproducts of its creation, such as the hazelnut skins left behind when creating a Nutella-like spread. But researchers at the University of California, Davis think these waste streams may actually be gold mines for our gut, providing new sources of prebiotics, nutrients that feed the “good” probiotic bacteria populating our intestines.

Prebiotics benefit health by influencing the amount and types of probiotic bacteria in the intestines. Typically, prebiotics are carbohydrates called oligosaccharides. The gold standard source of prebiotics is human milk, which contains oligosaccharides with very complex structures. Of course, the supply of this ideal source is limited.

“There’s just not enough human milk in the world to suddenly start selling that [as a prebiotic],” said David Mills, a UC Davis professor who studies bacteria that influence gut health. “We have been looking for different sources from different product streams … from wine to coffee … to find structures that might be analogous.”

UC Davis researcher Daniela Barile and colleagues have already identified some potential prebiotics in hazelnut skins, which are a byproduct leftover when hazelnuts are roasted for use in food products. Barile thinks the oligosaccharides found in the hazelnut skins will be more selective than prebiotics currently on the market, such as inulin and galactooligosaccharides, due to their more complex structure. In other words, they will be more likely to encourage the growth of specific types of bacteria.

“A lot of bacteria can thrive on those [inulin and galactooligosaccharides],” Barile said. “We don’t want that. We only want a few species of bacteria to grow.”

As I explained in a post last month, every type of probiotic bacteria is not beneficial to every disease or condition. Similarly, Barile said it’s important to have prebiotics that only encourage the growth of the desired types of bacteria.

With potential found in the hazelnut world, UC Davis researchers are now looking for prebiotics in coffee production byproducts, specifically the fruit that surrounds the coffee bean, which is removed in the production process. While prebiotics from these alternative sources aren’t currently available on supermarket shelves, the idea of repurposing waste to benefit our bodies seems like a venture worth tracking.