By Savanna Henderson, Humanitas Global
Though iodine was among the first nutrients recognized as vital to humans today, deficiency affects 780 million people worldwide. Inadequate intake of iodine can result in a number of disorders including: miscarriage, stillbirths, cretinism (permanent, severe mental retardation, deaf-mutism and motor spasticity disorders), goiters, impaired mental function, retarded physical development and hypothyroidism. Iodine deficiency disorder is the leading cause of preventable brain damage in children worldwide and deficiency alone can lead to IQ levels 10 to 15 points lower than those with adequate levels of iodine consumption. In 1990, it was found that nearly 30% of the world population was iodine deficient and 11 million people were affected by cretinism. When taking a closer look at Iodine Deficiency Disorder (IDD), it is found to characterize areas with low bioavailability of iodine in soils.
Regardless of food preference, lifestyle and consumption patterns, micronutrients come from the same source: the Earth. Minerals are naturally occurring substances in the Earth’s crust and vitamins are chemical substances found in food that is grown in the Earth or raised on plants. It is well understood that plant growth and crop yield depends on the nutrients present in the soil and as such, these nutrients can be modified to optimize both growth and yield. While some food plants and meat are richer sources of micronutrients, the soil is the predetermining factor of micronutrient levels in any plant. Crops grown in low-quality or deficient soils have lower nutrient content in both shoot and seed. Furthermore, soil type is an identifier of micronutrient deficient populations. For example, soils with low organic matter and highly weathered parent materials are prone to zinc deficiencies. Sedimentary rock, especially shale, is rich in iodine while igneous rock has very low levels of iodine.
While other nutrients, like zinc, are derived from the parent materials of the soil (minerals and organic material transported by water, ice, wind, etc. that make up soil) the majority of iodine in soils is derived from the atmosphere and ultimately, the oceans. But the organic content, texture, oxidation and pH condition of the soil (which parent material does have a role in) determines retention and concentration of iodine. Sandy soils and low clay soils report very low levels of iodine while clay-rich soils, organic rich soils and alkaline soils report much higher levels of iodine. Despite the high concentrations of iodine in organic-rich soils, the iodine is strongly fixed and in the form of iodate, which is insoluble to plants or the food supply. So, iodine deficient soils and iodine rich soils alike present problems for raising healthy, nutritionally robust citizens.
Be sure to check back for the follow-up to this blog that examines the potential for soil to improve nutrition in deficient populations and contribute to both nutrition and food security.