Soil and Human Health:
Correlation between soil composition and our well-being
We, human beings, live from about 25cm of topsoil, containing bacteria, fungi, earthworms and other forms of microscopic life, that sustain vegetation, insects, birds and animals.
Soil and human health are deeply interconnected, yet mainly ignored by our modern medical practices, that “treat” the symptoms, not the causes.
The soil is what feeds us throughout our entire lives, to gently embrace us back into the cycle of life when we are gone.
It’s the greatest natural resource we have.
True wealth is a fertile soil.
First links between the environmental geochemistry and human health were found in Chinese medical texts dated back to the third century BC, while in the West such information became more relevant around 1921-1959 thanks to pioneers like McCarrison,
Albert Howard, Eve Balfour, J.I.Rodale and André Voisin, who were writing about the links between soil and human health, in particular the effect of soil fertility on the nutrient content of foods.
In 1959 Voisin published a study on the potential links between soil and human health, which was probably the most comprehensive and extensive study on the subject up to that time.
In his book Soil, Grass and Cancer:
Health of Animals and Men is Linked to the Mineral Balance of the Soil he stated that
“all living things are biochemical photographs of their environment."
Our ancestors, were well aware of the fact that the dust of the soil itself is what finally determines vigor and health.”
His predicament about the increase of degenerative diseases in both animals and people as a consequence of overuse of artificial fertilizers progressed geometrically worldwide, to the present day.
The health and well-being of all living things on our planet, including plants, animal and humans, is directly connected to the health of the soil.
Soil study- Permaculture course (Sep 2020, Azores)
Micronutrients in Soil and Human Health
Usualy scientists say there are 14 elements essential for plant growth that come from the soil, and many of these elements are also essential for human health but some people of the regenerative movement talk about 90 and even 102 different elements we should have available.
These essential nutrients end up in the human diet either directly through the consumption of plants or indirectly through the consumption of animal products.
“In the pyramid of life, plants play an essential role, as man cannot ingest essential elements directly from the soil.
They must be brought to him through the good graces of living plants, which likewise feed all animals, directly or indirectly.
Via plant and animal our bodies grow out of the soil.”
(The secret life of plants, Peter Tompkins)
Hydrogen, oxygen, carbon, nitrogen, sodium, potassium, calcium, magnesium, phosphorous, sulphur and chlorine make up 99.9% of the atoms in the human body, with all but hydrogen, oxygen and carbon having soil as their major source.
However, the remaining 0.1% consists of approximately 18 additional elements (iron, manganese, copper, zinc, sodium, iodine etc) known as micronutrients or trace elements that are essential in small amounts to maintain human health.
These trace elements required by humans cannot be synthesized; therefore, there is a direct link between soil composition with its geographical particularities, food and health issues.
The diets of more than two‐thirds of the worlds population lack or are deficient in one or more essential elements, with more than 60% deficient in iron, around 30% in zinc, almost 30% in iodine and about 15% in sodium.
Dietary deficiencies of calcium, copper and magnesium are also prevalent in many countries.
Cardiovascular diseases are common where the soil is deficient in trace elements, as more recent investigations have suggested.
A study in the Netherlands showed that mortality from arteriosclerosis (hardening of the arteries) was greatest where the soil was formed from sea clay and peat, and least on sandy glacial soil.
Beeson & Matrone (1976) discovered more incidences on the Atlantic Coastal Plain of the USA where the soil is sandy, leached and often poorly drained, than on the Great Plains where the soil is muchless leached.
Shacklette et al. (1972) observed more disease on the coastal plain in Georgia than in the Appalachian Mountains where there is more variation in the soil.
Anaemia in sedentary populations was found to be linked to micronutrient deficiencies in the soil, especially iron.
Iron deficient soil can lead to small iron concentrations in plants and in humans who consume them.
This is especially problematic in arid soils and in populations whose diets rely on a large intake of cereal grains.
Iron deficiency causes anaemia because it is an essential component of haemoglobin.
About 25% of the world’s population and 47% of pre-school children are estimated to have iron deficiency making it one of the most common nutrient deficiencies worldwide, mainly in developing countries.
Selenium deficiency in Scandinavia has a similar distribution to that of iodine: both are prevalent on glacial soil.
This is because of the low temperatures, high humidity, low pH and large Fe concentration in the soil.
In the late 1970s it was shown that all agricultural products from Finland contained exceptionally small amounts of selenium, that apparently contributed to common diseases, especially cardiovascular ones and cancer (Varo et al., 1994).
Iodine deficiency has been identified as the single most preventable cause of brain damage world-wide by the World Health Organization, with other known effects such as congenital anomalies and delayed physical development.
Deficiencies are common in regions where soil does not supply adequate iodine to the crops grown in it, and although widespread, they are most common in the high altitude interiors of continents.
He observed that goitre was more frequent in the Alps than near the sea; a difference explained by the iodine content of soil and water. However, goitre was known to the Chinese possibly as early as 2700 BC, and around the fourth century AD they realized that seaweeds provided a cure (Ellis, 2001).
The main source of iodine in soil is from the oceans via atmospheric deposition in either rain or dry deposition.
There is no simple correlation between iodine in soil and distance from the sea, although the largest concentrations are typically 0–50 km from the sea. Iodine deficiency occurs worldwide; it is most pronounced in high mountain areas, inland areas of continents and some alluvial plains, being less concentrated in leached sandy soil and more in loamy clay soil.
The soils potential to fix and retain iodine depends principally on soil organic matter content, and humus might be the main reservoir of iodine.
In Romania people develop goitre on acid soil formed from conglomerates, sandstones and marls, whereas it does not occur on the near neutral chernozems- grassland soils rich in humus (Rauta et al.,1986).
Zhang (1987) noted that deficiency of iodine in the hills and mountains of Jilin Province, north-east China, gave rise to goitre.
Thilly et al. (1972) studied Idgwi Island in Kivu Lake (Congo) and found that goitre was common where the soil had formed on granites in the north of the island, whereas in the south-west, where the soil had formed from basalt, there was none.
Soil pH and nutrients availability
Among all the aspects that affect soil quality, like composition, proportion of organic matter, redox potential, moisture, human management, the pH is of particular importance because it controls the behaviour of metals and the availability of elements and essential nutrients for plant uptake.
Acid soil, which represents about 40% of the worlds agricultural land, has toxic concentrations of manganese and aluminium that limits crop production, whereas on sodic and saline soils (10% of agricultural land) too much sodium, boron and chloride mostly reduce crop production.
Alkaline and calcareous soils (25–30% of all agricultural land) have small availability of iron, zinc and copper, coarse‐textured, calcareous or strongly acidic soils contain little magnesium. Consequently, crops also have inherently small concentrations of certain elements.
Differences in soil moisture, acidity or alkalinity, arising naturally or from cultivation or irrigation, from industry or urbanization, can also affect the availability of specific elements to plants and the water supply.
Irrigation affects trace element availability.
If the water is alkaline it decreases the availability of zinc and enhances plant uptake of molybdenum and selenium.
Iron-rich water restricts selenium uptake.
In general the more acid the soil the more available are iron, aluminium, manganese and heavy metals such as lead and cadmium which can be harmful to health.
In addition, where the soil is acid, iodine and selenium are less available.
Human impact on soil quality
Composition and concentration of elements reflect the natural condition of the soil, however the anthropogenic or human impact is an alarming aspect that we simply cannot ignore anymore when we speak about soil-human health nexus.
Soil is the primary nitrogen source for plants, and given that nitrogen is required for human health, nitrate is an essential nutrient.
Plants can quickly diminish nitrate concentrations in soil.
For production agriculture to succeed, the nitrogen consumed has to be replaced frequently, and this is usually done with the use of chemical fertilizers.
Overuse and improper management of chemical fertilizers, among other faulty agriculture techniques applied worldwide, can lead to leaching of excess nitrate into groundwater or surface water.
Nitrate-contaminated water can cause serious toxicity when the gut microflora convert nitrate into nitrite, which reacts with haemoglobin, preventing oxygen from being carried throughout the body.
Nitrate has also been identified as a risk factor in the development of stomach cancer.
Soil degradation through irresponsible agriculture involves the depletion of nutrients and organic matter, increase in leaching, acidification, compaction, erosion, salinization, sodification and desertification.
Salinization in arid and semi‐arid regions from irrigation and internal drainage reduces biodiversity, efficiency in nutrient cycling and productivity, which increases food insecurity and diseases in plant, animal and humans.
Salinity, desiccation and drought reduce crop cover and increase wind‐borne dust, which leads to bronchitis and asthma.
Such dust often contains fungi and pathogens that affect humans (anthrax, Mycobacterium tuberculosis, influenza viruses, hantavirus).
Of the total agricultural land, 40% (2 billion ha) is degraded.
These adverse and cumulative effects reduce the soil capacity to sustain crop growth and animals and thereby have a direct impact on the quantity and quality of food accessible to human beings and their health, whereas pollution of surface waters by fertilizers and pesticides is an indirect effect.
Urban soil is contaminated from sources such as traffic, the combustion of leaded petrol, industrial manufacturing, mining, use of lead-based paints, recycling and disposal of wastes, application of lawn chemicals and so on, leading to toxic concentrations of heavy metals like lead, arsenic, cadmium, chromium, copper, nickel, mercury etc.
They affect local crops and human health directly.
Given the large numbers of people who live in urban centers (over 54% of the world’s population and increasing), particularly in developing countries, there is large exposure to these contaminants in this particular environment.
Lead and arsenic are probably the most relevant contaminants worldwide because they been widely introduced into soil from anthropogenic sources such as petrol (gasoline), lead-based paint, mining and smelting, and other industrial activities.
Mass lead poisoning was reported in Senegal in 2009 and Nigeria, in 2012, in villages that participated in informal recycling of used lead-acid batteries and gold ore processing, respectively.
The recycling and gold processing activities resulted in lead contaminated soil, with dust from such soil being inhaled, ingested or both, causing lead poisoning.
Soil has a large capacity to immobilize lead because clay and organic matter adsorb it.
The more lead there is in the soil the more concentrated it is in plants (Davies, 1995), and hence in food.
Arsenic is a naturally occurring element that can concentrate in drinking water, especially water obtained from wells.
Millions of people worldwide are exposed to potentially toxic levels of arsenic each day.
Another problem is the use of arsenic contaminated water to irrigate rice crops; the arsenic then accumulates in people who consume the rice.
Rice is the dietary staple for about half the world’s population, and for most of these people rice also represents their primary exposure to arsenic.
Biosolids , sewage sludge and animal slurries applied to agricultural land result in the introduction of pharmaceutical products in the soil, such as antibiotics, hormones, antiparasitic drugs and a large numbers of bacteria carrying genetic elements that are antibiotic-resistant.
Humans end up beings exposed to these antibiotic‐resistant genes or bacteria through crops, water and animal products, thus continuing the vicious cycle.
“A degraded habitat will produce degraded humans.”
Poor soil grows poor food, together with faulty farming and agricultural practices leading to disease, first to the land, then to the plant, then to the animal, then to people.
Healthy soil, with the proper composition of microorganisms produces strong, healthy plants which naturally repel pests, feeding healthy animals and strong healthy humans, that naturally develop immunity to diseases.
To keep these beneficial microorganisms and fungi in balance, consistent quantities of decaying organic matter need to be added to the land, returning to the soil what plants and trees took as nutrient.
In Permaculture this is accomplished by different techniques such as “chop and drop”, mulching, composting, cover crops, and basically turning “waste” into nutrition- it all goes back in the syntropic cycle of life.
With the growing awareness of the cyclic nature of life comes the opportunity of change, and the chance to break free from the destructive loop.
When we realize the reciprocity of our actions, we make better choices, making space for regeneration.
Our peace and well-being depends on the relationship we have with our natural resources.
Not their exploitation, but their nurturing-
a PERMAnent CULTURE of caring.
References and inspiration:
Happy Soil- Happy People, Permaculture internship (Sep 2020, Azores)
Soil, Grass and Cancer: Health of Animals and Men is Linked to the Mineral Balance
of the Soil, by André Voisin
Department of Soil Science, The University of Reading, Whiteknights, Reading RG6
WHO (1996) publication Trace Elements in Human Nutrition and Health