From soil to nutrition: micronutrients and heavy metals

Human nutrient deficiencies and toxicities can result from soil nutrient deficiencies and toxicities, e.g. when too low levels of essential micronutrients or too high levels of heavy metals occur. Contents in soils are determined by the substantial natural variation in soils and are influenced by fertilisation, cropping, weather and emissions from industrial processes. Bioavailability for plants is influenced by many chemical and physical soil characteristics such as pH, organic matter content, soil aeration, moisture, soil particle size, and interaction with other elements.

A proportion of the micronutrients and heavy metals in the soil can be taken up by plants. Effects of the amount taken up, e.g. on plant growth and development, vary among plant species.  Bioavailability and uptake is determined by soil characteristicsin interaction with crop characteristics (e.g. rooting depth and active or passive transport into the plant) and soil management practices. Plant internal distribution will ultimately determine the contents in the edible or harvested parts of the plant.

To lead a healthy and productive life, humans need a balanced supply of essential micronutrients and should limit the intake of heavy metals.

Retention of micronutrients and heavy metals in food items is determined by storage, processing and food preparation conditions, consisting of exposure to water, air, heat, UV light and oxygen. Bioavailability to humans is determined by food-related factors (e.g. diet, chemical form, binding to organic compounds, presence of inhibitors or enhancers of absorption, amount of the nutrient in a meal, nutrient interactions) and human-related factors (age, nutrient and health status of a person, physiological stage, fat mass, genetic factors).