The bewildering array of probiotic drinks in supermarkets these days is testament to the diverse and sometimes surprising health benefits of nurturing specific gut microbes. Consumption of probiotics directly supplies beneficial bacteria to the gut. A more subtle approach is to fertilize the gut with foods that contain components known to encourage the growth of good bacteria. A new study on pigs has shown that this strategy is not as straightforward as it at first might appear.

In a recently published paper in Nature Communications, Phillip Pope, Leszek Michalak and Bjørge Westereng, researchers at the Norwegian University of Life Sciences, described their work to promote the growth of two specific species of microbes that are known to produce the beneficial byproduct butyrate. The short-chain fatty acid is thought to promote a number of health benefits, from increased intestinal health to reduced cancer and diabetes.

“Since butyrate is associated with good gut health and low disease state, researchers around the world are striving to stimulate bacteria that produce it,” Pope says. He notes that humans are not the only ones that stand to gain from this effort. “While a major goal is public health, agriculture can also benefit,” he says. “If we can induce a healthy microbiome in livestock, it will help maintain the health of the animals.”

The researchers first had to find a compound that would selectively promote the growth of the two butyrate-producing bacteria but not other microbes, some of which could potentially have detrimental health effects. Based on chemical considerations, they identified a component in wood from Norway spruce–a carbohydrate named acetylated galactoglucomannan (AcGGM)–that seemed to fit the bill. They then fed weaned piglets diets containing various levels of AcGGM for a month, while monitoring the bacterial makeup of their guts and the proteins produced by their gut microbes.

Analysis of proteins from colon samples collected from pigs fed either the control diet or a diet containing 4% acetylated galactoglucomannan (AcGGM). The colors in the inner circle indicate the type of bacteria that produced the proteins. The dark colored spikes around the circle indicate the different levels of proteins between the two diets. In particular, the dark-green spikes show those bacteria enhanced by the diet containing AcGGM. Two bacterial species (MAG041 and MaG243) that produce butyrate are enhanced by the AcGGM diet. Credit: Reprinted with permission from Springer Nature 2020, Nat Commun 11, 5773

The results were both encouraging and perplexing. The researchers found that initially AcGGM did promote the growth of the two butyrate-producing bacteria in the piglets’ guts. But they also discovered that the levels of other gut microbes were affected in complex ways.

The finding demonstrates that while it is possible to develop compounds that promote the flourishing of specific microbes, the broader effects on the overall gut microbiota are more complex. “You might induce the good guys, but simultaneously you may spur the growth of other ones that perhaps have undesired effects,” says Pope. “Our results show that it’s critical to look at the whole picture.” 

To read more about the research, explore the paper in Nature Communications.

Phillip Pope is an Associate Professor with the Norwegian University of Life Sciences (NMBU). He obtained a PhD at Griffith University (Australia) in 2007 and worked with the CSIRO before moving to Norway in 2010 as a Marie Curie Fellow with Professor Vincent Eijsink (NMBU). An ERC starting grant enabled him to establish his own group in 2014 (@ThePopeLab), which today focuses on the microbiomes inhabiting important environmental ecosystems, production animals, wild animals and people.