What Does Soil Have to Do With Mental Health?

It’s well understood that getting in touch with the earth—literally—can be good for our mental health. The mechanics of this are simple: Direct skin contact with the incredibly diverse range of microbes in the soil directly impacts our microbiome, which itself is inextricably linked with our mental functions.

Yet soil affects the mind in ways that extend far beyond physical contact. Healthy foods grow from healthy soils. Our foods' nutritional content is directly correlated with the health of our soils. Finally, without the soil beneath our feet, we would not have the trees above our heads. The green spaces our bodies and minds rely on are directly dependent on soil.

Today, we see a broad range of quick-fix mental health solutions. Few may realize that nature’s answer lies below our toes.

Soil and the Gut Microbiome

In the modern world, we’ve long equated sanitized spaces with health. Yet our current understanding of the gut-brain axis challenges this assumption. We now understand that every bacteria in our gut has a function, from digesting complex carbohydrates and producing vitamins to regulating the immune system.

This is why bacterial diversity is so crucial. The broader the range of microbes we are exposed to, the wider the range of biological workers we have operating in our bodies. As stated by Dr. Elaine Ingham of the Soil Food Web School, "Everything nature does is done for a reason and done by biology, by the microorganisms."

This applies to our minds too. Microbes in the gut are responsible for the production of hormones like serotonin, which moderates both mood and behavior.

Studies show that exposure to a diverse range of microbes helps maintain a healthy gut-brain connection, which can buffer us against many mental disorders.

Where does soil come in? In just one teaspoon of healthy soil, there are more microbes than there are people on the planet. What’s more, humans share many of the same microbial groups as those found in soil. Most of the microbiomes of the human body are spread in the human intestines and skin.

The amount of human contact with the soil affects the diversity (and, therefore, health) of the human gut microbiota and gut health. Dr. Emeran Mayer, who directs the Digestive Research Disease Center at UCLA, explains that the microbiomes in the soil not only stimulate the production of polyphenols in the plants but also unpack them in the human gut, leading to their easier nutrient absorption.

Speaking about a recent report published by the Save Soil organization outlining the relationship between human health and soil health, Director of NHS Foundation Trust Board Sumita Hutchinson stated: “From nutrition to gut health to mental well-being—human well-being and soil health are intertwined. This analysis is important because it underscores how connected our health is to our natural environment.”

In short, to protect your mental health, you may have to get your hands dirty.

Soil and the Nutritional Content of Our Food

The connection between human health and soil health extends far beyond physical contact. The amount of nutrients found in our food is directly associated with the health of the soil it grows in.

Human physiological and psychological functions require macronutrients, namely carbohydrates, proteins, and fats, that provide the main source of energy for the human body.

Studies outline the link between depleting organic matter in soil and the impact it could have on our foods. Various studies show that the nutritional content of our food has dropped significantly since 1950. For example, one U.S. study found that the amount of important nutrients in some garden crops was up to 38 percent lower in 1999 than in 1950.

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This soil degradation has been attributed to intensive farming practices and excessive use of synthetic fertilizers.

Nutrient deficiencies in our food can have a real impact on our mental health. A research review suggests that dietary nutritional deficiencies can lead to the development of depression.

This is because specific vitamins in our foods are crucial for the production of neurotransmitters that influence mood regulation, such as serotonin. The proper functioning of the antioxidant system, which is involved in developing psychiatric disorders, depends on the density of nutrients.

Yet this trend of depleted nutritional content in our foods is not irreversible. Studies reveal that foods grown using regenerative farming methods can have increased nutritional content. One study revealed that crops grown through regenerative practices were about 30 percent higher in vitamins K, C, E, and B1 than their conventionally grown counterparts.

Speaking about the link between our soil’s health and human health, Dr. Uma Naidoo of Harvard Medical School has said, “The biodiversity of the soil really impacts the biodiversity of your gut microbiome, and the health of your microbiome is related scientifically to healthy changes in your body and brain. Thinking about the foods you eat mindfully can have a real impact.”

Ancient wisdom suggests that the health of all living things is inextricably linked. Modern science reveals that this link can be found in our soils.

Soil and the Great Outdoors

Finally, the link between spending time in green spaces and improved mental health has been established. From the Japanese practice of Shinrin Yoku, or ‘forest bathing,’ to the NHS’s ‘Green Social Prescribing in the UK,’ time in nature has been proven to boost mental health.

A review study investigated the effects of forest bathing on salivary or serum cortisol levels as a stress biomarker to understand whether forest bathing can reduce stress. Results showed that cortisol levels were around 16 percent lower in groups exposed to forests compared with those exposed to urban areas.

Yet again, soil is the silent hand governing our health and wellness.

The link between human health and soil health is growing clearer with every study conducted. That’s why it’s time to stop thinking of soil as the dirt that must be avoided. Instead, it is the one organism that protects all others.