“What we Eat”A Study From The National Research Council

Cindy MillanES 408

The Issue • Ingestion of earth soil by humans is a public health issue.

• Ingestion of soils occurs in one of two wayDirect: intentionally or consciously eating soilsIndirect: via eating (Contaminated foods etc.)

Direct Ingestion (Geophagia)

Geophagia/Geophagy: the direct consumption of soil or clay

Documented in historical timesRemains a current practice todayPractice increasing in Western society's through introduction

by several immigrant groupsSoils can be purchased in ethnic food stores that attract

specific cultures and spark interest for others

Direct Ingestion Cont.

Human/Animal Nutritionist Perspective

Acquired Habitual Response: Ingestion of soils in order to reduce toxicity of various environmental components

Innate Response: As a response to nutritional deficiency

Direct Ingestion Cont.

Problems associated with GeophagiaAssociation with mental health disorderBalancing habitual responseIncreased exposure to toxins

Microbe Effects on Earth Material• Surface soils provide a means for food production • Plant nutrition is the result of balanced earth characteristics

Free living microbes in rhizosphereSymbiotic associations between rhizobia and mycorhizal fungiSuppression of pathogens

Microbe Effects cont.• Human health and Soil-Bourne pathogens

Pathogenic organisms in soil can infect cropsAntibiotic take up by plants affects human health too Adherence of pathogens to unwashed products most common

Microbe Effects cont.• Helminthes (Worms)

Roundworms*FlatwormsTapeworms

• Most commonly ingested in developing countries and in southeastern

• Further causing anemia, vitamin deficiency's & GI blocks

Trace Elements & Metals in Earth Material• Toxic and beneficial trace elements present in soil

Soil parent mineralAtmospheric deposition of natural materials (Ash)Anthropogenic inputs

• Trace element conc. in soil VariespH 6-8 increases absorption of many minerals (Ag, Au, Cr and F) Increases conc. of other elements may not effect animal health

Trace Elements & Metals in Earth Material

Bioaccumulation of Trace Toxic Metals

• Cadmium Result from crops growing in soils high in cadmium contentOccupational exposureExposure through domestic items (Plastic, batteries and metal

coating)

Disease in humans occurs mainly through long term consumption of contaminated rice resulting in proximal tubular dysfunction

Japan: Mining and smelting resulted in contamination of rice paddy soils

*Individuals in this area were consuming 600mg/day

Bioaccumulation cont.• Selenium

A protective factor? Ecological studies have found an inverse correlation between

selenium levels in soil and mortality from cancers (Specifically prostate) Study: Men taking selenium supplements for a period of 5 years=

65% reduction incidence of prostate cancer 9 year follow up found no correlation between base selenium levels

and prostate cancer

Most studies looked into relationship between selenium supplementation and cancer risk, none have focused on relationship between low- selenium bioavailability and cancer risk

Bioaccumulation cont. • Zinc

Found in red meat, poultry, grains, dairy, legumesCritical soil nutrient

• Zinc as a protective factor?There is evidence that zinc inhibits replication of prostate cancer

cell growthCancer cells (from prostate tumors) lose their ability to amass

zinc• Reduced red meat consumption and increased cereals in diet

may attribute to zinc deficiency

Conclusion

There is much research and collaboration opportunity!

High priority research should focus on the following:1. Determine the influence of biogeochemical cycling of trace

elements in soil and its critical relationship to low dose chronic exposure through food and the influence on human health.

2. Determining distribution, survival and transfer of human and plant pathogens through soil

3. Improve public understanding of the relationship between disease and metal speciation (and that of disease and non-metal interaction)

References

National Research Council, 2007, Chapter 5- “What we Eat”