Good Dirt: How the Bacteria in Healthy Soil Can Improve Your Health

We all wash our fruits and veggies before eating them. At least we should, because they may harbor illness-causing germs even if they look clean. But what if I told you that where and how your produce was grown has a major impact on whether the microbes on its surface will help or hurt your body, how clean it is before it reaches your kitchen, and even the nutritional value of the food? Read on to find out more, and to learn how you can improve the health of your intestinal tract and indeed your entire body by choosing foods from optimal sources. 

Good Bugs, Bad Bugs

How important is it to thoroughly wash fruits and veggies before eating them? The answer to that depends largely on where the produce came from and how it was grown. Bacteria, viruses, dust, mold…all of these can be invisible to the naked eye, with the ability to make us sick even though we can’t see them. Washing your produce with soap and warm water and rinsing it very well (because you don’t want to eat soap either) is one of the most basic ways to avoid foodborne illness.

However, not all microbes are created equal.

Bacteria, along with viruses, protozoa, and a host of other microscopic bugs, are everywhere. Literally. On your hands (even after you wash them), in the air, in the water, and especially in the ground. Before you pull out the disinfectant, let me assure you that many of these tiny bugs are helpful rather than harmful. Our bodies are actually comprised of more bacteria than cells, in fact. Scientists estimate that the human body houses around 1,000 different strains of bacteria, roughly 39 trillion bacterial cells total, compared to only 30 trillion human cells. Some of these bacteria can absolutely make you sick, but only if their numbers get out of control. Most of the bacteria, however, are not only beneficial for your body, they are essential for maintaining optimal health. Good bacteria are the workhorses of the gastrointestinal (GI) tract, where about 70% of your immune system resides. The GI tract is one of the body’s first areas of defense against outside invaders (along with your skin and mucous membranes). The beneficial bacteria in your gut work to maintain a healthy environment for your immune cells, so that they can do their job effectively and keep you from getting sick. Excellent gut health is achieved by striking a balance between the good and the bad bugs. Both will always be present in your gut; your job is to feed the good bacteria so that they can outnumber the bad guys. Read on to find out how to do this. Thankfully, it involves some delicious food!

You’ve probably heard of probiotics, and maybe also prebiotics. Probiotics are good bacteria found in certain food sources, such as yogurt and other fermented foods like kefir and sauerkraut. Prebiotics can be thought of as fertilizer for your beneficial gut bacteria, and are found in foods high in resistant starch and fiber. Because the human body cannot either one, they pass through the intestines and feed your good bacteria along the way. Some of the top prebiotic food sources include asparagus, bananas (especially green ones), sweet potatoes, dandelion greens, apples, and onions. Both prebiotics and probiotics are important for a healthy GI tract, to feed the good bacteria and to maintain a favorable environment so that bad bacteria don’t thrive.

Now let’s take a look at the soil. Just one teaspoon of healthy soil contains between 100 million and 1 billion bacteria. While a subset of soil bacteria are pathogens (those that can cause disease), by far the greatest numbers of soil bacteria serve the important purposes of retaining nutrients, reducing water loss, and breaking down organic matter in order to help plants grow strong and healthy. Importantly, they also work to suppress pathogenic bacteria. Most of the bacteria found in healthy soil (that which is not laden with pesticides, herbicides, and fertilizers) is not even harmful to humans. Which is not to say that eating dirt is a good idea. As we’ve discussed, there are pathogens in healthy soil too, but beneficial bacteria that work to improve the health of plants and our health far outnumber the disease-causing bacteria.

How to Find the Good Stuff

Now that you know a bit about bacteria, how can you find food that has been grown in healthy soil, providing as much good bacteria for your body as possible? Studies have shown that the soil on organic farms contains both a higher number and greater variety of beneficial bacteria, as well as more beneficial fungi and earthworms. All of these organisms work together to further enhance soil quality, meaning that with each growing season and each addition of compost and organic matter to the soil, the quality continues to improve. This translates into better food for us – better in terms of nutrition and taste.

Thus, finding a farm that produces their food according to responsible growing practices is paramount if you are serious about eating the healthiest food you can afford. To clarify, “responsible growing practices” used to mean looking for the label “organic.” Then “local” was the buzzword. Now there is a third term to watch for: “biodynamic.” A farmer who uses biodynamic growing practices actively works to improve the health of their soil, and thus the plants they grow in that soil, with various methods. These methods include incorporating compost and other organic matter from their own farm into their soil, rotating the crops grown in a given site, planting cover crops in the off season, and using animals to help turn and fertilize the ground. Biodynamic farming incorporates all of the tenets of organic growing but then takes them several steps further, with the ultimate goal of being completely self-sustainable. Some might say that biodynamics is the epitome of responsible farming: great for the environment, the land that the farmer owns, and the body of every person (or animal) who eats the food.

How do you find food that has been grown with organic and/or biodynamic practices? Start by shopping at your local farmer’s market whenever possible. There you can often talk with the grower, and ask them the following questions:

“How was this grown?”

“When was this food harvested?”

“Has it been sprayed? (If so, with what? A substance approved for organic gardening is much better than a conventional product.)

Talking to the producer about the methods they use to grow their food will quickly give you an idea of how healthy it will be for your body. As a producer who has sold at farmer’s markets, I can assure you that most farmers are more than happy to share details of their production methods. Those of us who take the time to improve the soil before any plants are growing in it have a greatly reduced need to spray anything on our plants, which in turn reduces the need to scrub noxious germs and/or chemicals off of the produce with soap and water. Now, I am not telling you not to wash your produce! Washing your food before eating it (especially if you are eating the peel) is as essential as washing your hands before you eat. But, what I am saying is that if you grow the food yourself or buy it from a local producer who has grown it without chemicals, you can simply rinse it well and eat it, giving yourself all of the nutrition and the beneficial bacteria that are on the food, as well as avoiding any pesticides, herbicides, and many of the pathogens that would be on conventionally-grown produce.


Brevik, E.C., & Burgess, L.C. (2014) The Influence of Soils on Human Health. Nature Education Knowledge, 5 (12): 1 

Ingham, E.R. The Living Soil: Bacteria. Retrieved from

Mayo Clinic Staff. Prebiotics, Probiotics and your health. May 21, 2019. Retrieved from

Sender, R., Fuchs, S., & Milo, R. (2016). Revised Estimates for the Number of Human and Bacterial cells in the Body, 14 (8), doi: 10.1371/journal.pbio.1002533

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