Feeling low this winter? Here’s why your body might need soil microbes

Getting dirty is good for your health – it’s official. We’ve long known the benefits of getting out in the garden for helping brighten our spirits – after all, a dash of winter sunshine and fresh air can do wonders for the soul. But scientists have now found that direct exposure to soil and soil microbes can help alleviate depression and stress.

A new study from Korea, published in the journal Nature in August 2025, found that direct soil exposure alleviated depression-like behaviour in mice, thanks to the presence of Streptomyces rimosus. This soil microbe is known to produce the natural compound geosmin, which gives soil its distinctive, earthy smell and has been found to have positive effects on mental health.

Research from Konkuk University, Seoul, published in 2025 and using the same soil microbe, found that the inhalation of compounds from soil during horticultural activities helped alleviate depression, reduce stress and enhance relaxation in 30 volunteers. Furthermore, a study from the University of Helsinki and University of Tampere in 2018, published in MicrobiologyOpen, found that people who handled soil for 20 seconds, three times a day – then rinsed with water – had increased diversity in their microbiota, which is thought to have beneficial effects on human health.

The hygiene hypothesis – the idea that children need to be exposed to germs in order to develop healthy immune systems – suggests that reduced contact with natural biodiversity and increased hygiene levels are related to an increase in immune‐mediated diseases, so that’s even more reason to reconnect with your garden.

Making the connection

So what is it about soil that’s so special? According to the Soil Association, one teaspoon of healthy soil holds more microbes than all the people on Earth, and studies are increasingly showing how exposure to soil-bound microorganisms can strengthen our immunity.

There are lots of similarities between soil and the human gut – they contain approximately the same number of active microorganisms per gramme of material, although our gut microbiome diversity has decreased dramatically over the years, thanks to our modern lifestyles. Research has shown that increased microbial activity may contribute to increased gut microbial diversity. This is important because gut microbes are key to many aspects of human health.

‘Research shows that gardening can be great for our gut health,’ explains Dr Megan Rossi, gut health scientist and founder of The Gut Health Doctor. ‘One study from the University of Illinois Urbana-Champaign [2022] compared families who regularly gardened with those who didn’t, and found that the green-fingered families had a more diverse range of gut microbes, which is linked to better overall health, as these microbes play a key role in digestion, immunity and even our mental wellbeing.’

Exposure to garden soil is also thought to build tolerance in your immune system and protect against allergies and asthma. Numerous studies suggest that exposure to soil in early childhood can help reduce the likelihood of these ailments. So it really does makes sense to listen to your granny and let your kids loose in the garden making mud pies.

‘People with a more diverse gut microbiome tend to have stronger, more resilient immune systems, as around 70 per cent of our immune system is found in the gut,’ says Dr Rossi. ‘Research shows that greater gut diversity – which can be supported through the microbes found in soil – is linked to a reduced risk of up to 70 chronic conditions, including heart disease and type 2 diabetes.’

Soil health and food

The foods we eat also have a direct effect on our gut microbiome. Currently, there’s a booming interest in regenerative farming, which promotes biodiversity to allow soil, water and nutrients to regenerate themselves, leading to increased levels of nutrients in our food. ‘We’re starting to understand vital links between soil health and human health,’ says Dr Lucy Williamson, registered nutritionist and gut health expert. ‘Foods grown in healthy soils from nature-based farming systems are richer in microbes – as well as certain nutrients and antioxidants – than those that aren’t grown in this way. It follows that by supporting soil biodiversity in nature, we support the microbiome within us and, ultimately, our overall wellbeing.’

Dr Williamson explains how, in nature-friendly farming systems, where pesticides aren’t used, crops can’t depend on chemicals to protect from disease, so they build their own defences by increasing their antioxidants. ‘These are like rocket fuel for our gut microbes,’ she says. ‘If we choose food that’s organic or has been farmed using a regenerative farming system, generally we find that the levels of antioxidants are higher. And eating foods rich in antioxidants is one of the top four ways to look after your gut health.’

Taking care

But if handling soil is good for our gut, what about current advice that suggests gloves should be worn when gardening, to minimise the risk of disease? ‘Glove-wearing may be sensible to avoid physical injury, but a tetanus vaccination is essential if working with soil,’ advises Kevin Butt, Reader in Ecology at the University of Lancashire. ‘This helps protect against a deep or soil-infected injury. Nevertheless, the feeling of soil on injury-free hands can be quite therapeutic, particularly when potting plants.’

However, you don't have to wear gloves for all gardening jobs – many people prefer gardening with their hands au naturel, and find it easier to weed and plant seeds with direct contact with the soil. What’s most important is to use good judgement, always taking care to cover up any cuts, washing your hands thoroughly after gardening, ensuring your jabs are up to date, and always wearing gloves when handling manure, chemicals or working with potentially harmful plants or cutting tools.

And, whether or not you’re getting a mental boost from garden soil, simply being outside can help lift your spirits – that’s one good reason not to hibernate this winter!