Health-promoting microbial diversity missing from dietary recommendations

Health-promoting microbiological diversity is missing from the plates and guts of many. According to a review by the Natural Resources Institute Finland (Luke) and Tampere University, eating safe microbes from the soil can promote the development of our gut microbiota and immune defence, and have a positive impact on our mental health.

Soil microbiota was essential in the evolution of the human gut microbiome and immune defence. An adult can have 1.5 kg of gut microbes in their gut and several hundred or thousands of different species. Most microbes are bacteria, which produce compounds that regulate metabolism, endocrine function, and inflammatory factors, among other things.

Today, soil microbial diversity is missing from the plates and guts of many. According to a recent review, this may be one of the biggest causes of many of today’s health problems.

The diversity of gut microbes has declined along with urbanisation, western diets and global biodiversity loss. At the same time, the prevalence of chronic, non-communicable inflammatory diseases has increased in urbanised societies. Imbalances in the gut microbiota have been linked to obesity, cardiovascular disease, diabetes, inflammatory bowel diseases, central nervous system disorders and allergies, among others.

-Our gut microbial diversity may be compatible with our urbanised environment, but at odds with our human biology, Marja Roslund, a Research Scientist at Luke, commented on the findings in a review published in the journal People and Nature.

More research into the health benefits of eating soil

In an extensive literature review, Dr Roslund, Principal Scientists Aki Sinkkonen and Olli Laitinen reviewed the scientific evidence on the benefits and harms of soil microbial ingestion.

According to the review, human studies have shown that exposure to soil microbes modifies the human microbiota, which may have a positive effect on immune defence. For example, in gardening families, soil microbes have been found to be passed throughout the gut of the whole family, even if there was only one gardener in the family. Animal studies have shown that exposure to soil microbes can balance gut homeostasis, prevent allergies and autoimmune diseases, and reduce anxiety and stress.

The review also identified current research gaps and challenges that have hindered research and exploitation of the effects of soil microbial ingestion for health promotion.

-The literature search did not find any studies in which volunteers intentionally ingest safe and tested soil microbiota for health promotion. The studies have focused more on the risks of soil ingestion than the benefits, indicating a critical research gap, Roslund commented.

Safe soil microbes could be part of nutritional recommendations

A planetary health diet contributes to the health of the planet and people. It consists largely of vegetables, fruits, whole grains, legumes, and unsaturated fat-rich oils and can also include moderate amounts of fish and chicken but only a little red meat. However, soil microbial diversity is missing from the dietary recommendations and from the planetary health diet.

In many cultures, people have eaten soil either by accident or on purpose to remove harmful substances from the body and because of nutrient deficiencies. The phenomenon is still common among some indigenous peoples, especially during pregnancy. Soil microbes can also be eaten unconsciously

-We eat soil microbes because they are inevitably transported by the plants that grow in the soil. Or at least we do if our diets include a wide variety of organic crops grown in clean and microbial-rich soil, says Sinkkonen.

However, eating soil directly from the ground is not safe, as many pathogens and harmful substances can be present in the soil. Heavy metals, petroleum hydrocarbons, microplastics and pharmaceutical residues can be found in soil. In addition, antibiotic-resistant bacterial strains, pathogens and parasites, such as helminths may be present.

While probiotics have been shown to promote gut balance and health, they often contain only one or two strains of bacteria that have been studied. Microbial diversity has not been considered, despite studies showing that it may have beneficial health effects.

-We need new technologies and especially research and development to harness the beneficial health effects of soil microbes for society while avoiding the risks associated with soil consumption. This development can have far-reaching public health and economic benefits, says Laitinen.

The study was funded by Valio Oy. The literature review was carried out in collaboration with the Natural Resources Institute Finland (Luke) and the Tampere University in the Strategic Research Council’s research programme Environmental and Social Links to Biodiversity Loss (BIOD), the Biodiversity Interventions for Well-being (BIWE) project. Research Scientist Marja Roslund and Principal Scientist of Environmental Ecology Aki Sinkkonen from the Natural Resources Institute Finland, and Olli Laitinen from the Tampere University, Principal Scientist in Molecular Virology, participated in the research.

Link to the publication: Scoping review on soil microbiome and gut health – are soil microorganisms missing from the Planetary Health Plate?

The news is published on Luke’s website 25.4.2024.

For more information, please contact Marja Roslund, marja.roslund@luke.fi, +358295322256