New research suggests the unique blend of fungi and bacteria in a region’s soil is more strongly linked to childhood allergic disease rates than demographics, wealth or climate.
Although a causative connection has yet to be established, the researchers say the pattern appears with remarkable consistency across the globe.
“We’ve analyzed the data in every way we can think of—adding datasets, looking at different measures of soil diversity…no matter how we’ve done it, this result is consistent,” said co-author Joshua Ladau, a microbial ecologist at Arva Intelligence, a farmer-focused environmental solutions company. “At this point, I’m exceedingly confident this association is real.”
Allergic disease affects an estimated 2.5 billion people worldwide, or roughly 30% of humanity. A growing body of research suggests that exposure to a diversity of microbes as a child can help limit allergic disease, but significant data is missing—including how soil microbes stack up when comparing with things like access to health care, genetics, climate and pollution.
“Soils are not generally the things people point to first when thinking about health,” said Ladau.
To try to answer this question, Ladau and colleagues at Oak Ridge National Lab, University of California and California State University Fresno hit the data—hard. They drew on datasets recording the prevalence and severity of atopic dermatitis, asthma and allergic rhinitis among over 1 million children in more than 250 cities across 97 countries, plus three global surveys of soil fungal and bacterial diversity amounting to over 8,200 soil samples from around the globe. The researchers then used a model to tease out the associations between the disease rates and soil biodiversity represented in the data.
Based on the massive dataset and model, the team concluded that soil microbes are up to four times more predictive than the next most important variable in terms of both disease prevalence and severity.
The study showed simply having a broader diversity of microbes is not the important criteria—rather, it’s which microbes are present.
“It looks like there are a number of taxa that are promoting health, and ones that are negatively associated, “Ladau said.
The negative microbes are newly identified and weren’t already known as pathogens, adding to the novelty of the discovery.
In addition to establishing whether the connection is causative, the research team said they want to investigate ways to promote public exposure to potentially healthful soils. The obvious way to do this is by encouraging people to spend more time outdoors, but it can also be accomplished through policies and land management strategies aimed at conserving and restoring soil. This, in turn, will improve soil’s ability to sequester carbon, remediate fire damage, decompose detritus and control pest prevalence.
“Linking soil biodiversity to public health provides a major additional facet to the importance of soils and what’s living in them,” said Ladau.
The microbiologist presented this research on Tuesday at AGU25, where more than 20,000 scientists convene to discuss the latest Earth and space science research.