Food Crops: Nutrient Fluctuations and Malnutrition

Climate change and other factors such as topsoil erosion, land management practices, and agricultural methods affect availability of food crops and potentially impact their associated nutrient levels.^1-6 Recent research notes that atmospheric carbon dioxide (eCO₂) levels may contribute to the fluctuation of nutrient availability in soil and nutrient uptake by crops, as well as the resulting levels of minerals and proteins in those plants that are ultimately consumed by people.^2,5,7,8 The climate-related mechanisms for declines in plant mineral composition are not completely understood, and the argument is made that eCO₂ potentially enhances overall crop yield, which may be a benefit in some situations, even if the mineral quality of the crop is decreased.²

When considered through a nutritional lens, the human body requires certain levels of these micronutrients for normal body processes, and deficiencies in one or more micronutrients may lead to detrimental health issues and chronic disease. Already, several nutrient shortfalls have been noted within the US population, most people in the US do not consume the recommended amounts of fruits and vegetables per day, and analysis of National Health and Nutrition Examination Surveys (NHANES) suggests that an estimated 31% of Americans are at risk of developing micronutrient malnutrition.^9-11 Several factors may contribute to mineral deficiency, including dietary patterns and the prevalence of a Western-style diet consisting of more processed foods and less vegetables. Additionally, declining nutrient density of food crops has the potential to exacerbate micronutrient malnutrition on a global scale, as well as in our own backyard.

A focus on soil

Soil is made up of organic material in addition to particles of minerals and rock, liquids, and gases. An important indicator of soil health is soil respiration, which is essentially a measure of carbon dioxide (CO₂) released from the soil due to the decomposition of organic matter by microbes within the soil and the respiration of plant roots and fauna.¹² This measurement indicates the level of soil microbial activity, the nutrients available in the soil for uptake by crops, and the soil’s ability to sustain plant growth.¹² Essential soil respiration rates depend on factors such as the amount and quality of soil organic matter, temperature, salinity, pH, the circulation of air, and moisture.¹²

Maintaining a diverse soil biota is essential for agricultural sustainability for both productive and nutrient-dense crop yields.¹³

In 2016, a government report on US soils suggested that land-use changes in the past 50 years have contributed to reduced ecosystem functions.⁶ When combined with intensive agricultural practices and soil contamination, this has the potential to reduce soil microbial abundance and impair other functions such as decomposition and nutrient retention.⁶ In addition, a 2017 European Environment Agency report indicated that effects of climate change have been seen globally and in European soil, with moisture levels significantly decreased in some regions and increased in other regions since the 1950s.¹⁴ Climate factors can also affect the level and availability of nutrients such as nitrogen, phosphorus, potassium, and iron in the soil.² One consideration is that warming air temperatures and increased solar radiation may lead to higher soil temperatures, resulting in more microbial activity, higher soil respiration rates, and potential limitations in soil nutrient availability.⁶