What's in the Soil Is in You

Pick up a handful of good soil sometime. Not the stuff in a bag from the garden center, not the sandy substrate scraped flat by a tractor. Actual living soil from a field that has been tended for years: dark, faintly sweet, dense in a way that feels like it has purpose. There is more biology in a teaspoon of healthy soil than there are people on earth. Bacteria, fungi, nematodes, protozoa, arthropods, all of them cycling nutrients, breaking down organic matter, threading mineral pathways toward plant roots. You cannot see any of it. You just feel the weight of it in your hand and know that something important is happening.

Most people don’t think about soil when they are eating a salad. That seems like an obvious thing to say, but let's consider it for a minute, because the connection is more direct than we tend to account for. The minerals in your food do not come from thin air. They come from the ground the plants grew in, mediated by the microorganisms that made them available.

Healthy soil does not just support plant growth. It influences what the plant actually contains.

A study published in the Journal of the American College of Nutrition compared USDA data on the nutrient content of 43 fruits and vegetables between 1950 and 1999. Across those five decades, six out of thirteen nutrients studied had declined by 9% to 38%, including calcium, iron, phosphorus, riboflavin, and vitamin C. Not vanished, just quietly diminished. The vegetables looked the same. They weighed the same. They just contained less of what they were supposed to contain.

More recent research has pushed that finding further. A 2024 review in PMC found that in the last sixty years there has been what the authors called "an alarming decline" in the mineral and phytochemical content of food crops, with synthetic fertilizer practices, soil disturbance, and the disruption of microbial communities among the primary drivers.

A landmark study by soil scientist David Montgomery and biologist Anne Biklé, who reviewed close to a thousand studies for their book What Your Food Ate, compared paired regenerative and conventional farms across the United States and found that regenerative fields, with twice the topsoil organic matter, produced crops with measurably higher levels of vitamins, minerals, and phytochemicals. The soil that had been tended differently grew food that was nutritionally different.

The process is not magic. It is mycorrhizal fungi, the threadlike networks that extend plant root systems by orders of magnitude, trading sugar for minerals the plant cannot reach on its own. It is the bacterial communities that cycle nitrogen in forms plants can use. It is the aggregate structure of living soil that holds water and allows roots to penetrate and explore. Disturb that biology repeatedly, and crops can still grow. They will just have less access to what they need, and so, eventually, will we.

There is another human health angle here that usually does not make it into the farming conversation, partly because the people most exposed to the consequences of degraded soil are also some of the people least likely to be publishing about it:

Farmworkers. The people who are actually in the field, planting, cultivating, harvesting. They are breathing whatever is close to the ground, diesel exhaust from walk-behind equipment running at handle height, pesticide drift, particulate matter from dry soil turned over repeatedly. The International Agency for Research on Cancer classified diesel engine exhaust as a "Group 1 carcinogen" in 2012. Farmworkers have some of the highest occupational exposure to diesel exhaust of any labor category, and among walk-behind tractor operators that exposure is particularly concentrated because the machine shoots the exhaust stream right at breathing height.

This is a soil health story too, just a few steps removed. Degraded soil requires more inputs to maintain yield. More synthetic fertility, more chemical pest control, more equipment hours to compensate for what the land cannot do on its own anymore. Each of those inputs circles back to the people working closest to the ground.

The practical implication is not that everything is broken and fixing it is impossible. It is more that the health of the food, the health of the land, and the health of the people working it are not separate conversations. They run on the same thread.

Practices that protect soil biology, reduced tillage, cover crops, organic matter returned rather than extracted, equipment light enough not to compact the structure you are trying to build, all of them contribute to the same outcome from different directions.

The spinach has more iron. The field holds more water. The operator breathes cleaner air at the end of the row. It’s just biology, moving slowly enough that we stopped noticing it was happening.

You grow food in soil. What the soil is doing, or failing to do, ends up in the food. And then, eventually, it's inside you.

Sources

Davis et al., "Changes in USDA Food Composition Data for 43 Garden Crops, 1950 to 1999," Journal of the American College of Nutrition, 2004

Montgomery & Biklé, What Your Food Ate, W.W. Norton, 2022; summarized at The Organic Center

Montgomery et al., "Soil health and nutrient density: preliminary comparison of regenerative and conventional farming," PeerJ, 2022, PMC

Mie et al., "Human health implications of organic food and organic agriculture," Environmental Health, 2017, cited in Frontiers in Sustainable Food Systems

IARC, "Diesel Engine Exhaust Carcinogenic," press release, 2012; IARC

Zhu et al., "An Alarming Decline in the Nutritional Quality of Foods," PMC, 2024