In the US, soil is often casually called "dirt." It's what you wash off your hands, sweep off the floor, and scrub from vegetables. Soil, earth and clay are older words, and they say something truer: this is the material that every living thing on land depends on, including us.
Most of us are disconnected from that. We think of nutrition as something that starts in a supermarket or a supplement bottle. It starts in the ground.
What soil actually is
Healthy soil is a living system. It's made of weathered rock (the source of its minerals), decayed plant and animal matter, water, air, and billions of microorganisms in every teaspoon: bacteria, fungi and other tiny life forms, plus larger residents like earthworms. Clay and organic matter act like a storehouse, holding onto minerals and releasing them slowly so roots can take them up.
That's why "dirt" is such a poor word. Dirt is what's left when soil has been stripped of its life.
How soil becomes your body
Plants can't make minerals. They can only draw up what is already in the soil around their roots, and most of them get help from partner fungi (mycorrhizae) that extend their reach and help them absorb minerals like zinc and phosphorus. Animals eat those plants, and we eat both.
So the chain runs: rock → soil → plant → animal → you. The zinc in an egg, the selenium in a Brazil nut, and the iodine in a glass of milk all started in the ground. If a link in that chain is weak, the mineral content of the food at the end of it can be too.
How soil gets depleted
Modern farming has done a lot of good, feeding far more people than was ever possible before. But some of its methods can wear soil down over time:
- Intensive tillage and monocropping reduce the organic matter and biological life that help soil hold and release minerals.
- Synthetic fertilisers replace nitrogen, phosphorus and potassium, the nutrients that drive yield, but not the full range of trace minerals.
- High-yield crop varieties can grow bigger and faster without taking up proportionally more minerals, so the minerals get diluted. Researchers call this the dilution effect.
- Erosion carries away the topsoil, which is the most mineral- and life-rich layer.
Several studies comparing food composition tables from past decades to today's have found lower levels of some minerals in some crops. The size of the decline is debated, but the direction of concern is clear enough that it's worth taking seriously.
Geography matters too
Some soils are low in certain minerals simply because of geology and climate. Heavy rainfall and past glaciation tend to wash minerals like iodine and selenium out of the ground, and Irish soil is naturally low in both. That's why farmers here often add selenium and iodine to livestock feed, since pasture alone can fall short, and why intake of these minerals in Ireland can run low even when someone eats well. It's also why mineral-rich foods like fish, eggs and dairy matter more than they might seem to.
Soil and your immune system
There's a second connection that goes beyond minerals. Early research suggests that regular contact with diverse soil microbes, through gardening, time outdoors, and eating food grown in living soil, may help train and diversify our own microbiome and immune system. The evidence in humans is still developing, so it's too soon to make big claims. But it fits a pattern: we evolved in close contact with the earth, and we've largely moved away from it.
What you can do about it
You can't test the soil under your dinner, but you can stack the odds in your favour:
- Eat a varied, whole-food diet that includes the foods that concentrate minerals: seafood, eggs, organ meats, nuts, seeds and pulses.
- Choose producers who look after their soil, such as regenerative and organic farms, where you can. The direct nutritional benefit to you is still being researched, but healthier soil is the right direction.
- Grow something yourself. Even herbs on a windowsill or a small raised bed put you back in touch with the process.
- Don't assume a "good" diet is enough. In Ireland, iodine and selenium are two minerals where a gap is common, and it's worth checking rather than guessing.
If you're not sure where your gaps might be, our FREE Health Questionnaire is a good place to start.
We are made from the same minerals that are in the ground. It's not dirt. It's where we come from, and it's worth looking after.
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