Metals in Leafy Greens Can Be Reduced by Better Understanding How They Move in the Soil and Plants

Washington D.C. — The sensitivity of children to heavy metals and toxic elements has led the U.S. Food & Drug Administration to establish a ‘Closer to Zero’ initiative to reduce them in the food supply. This often involves addressing food groups like fruits and vegetables.

Leafy greens like spinach, kale and lettuce can absorb metals like cadmium and lead which are often naturally found in the soil but do so in different ways and in different parts of the plant.

A new study led by Dr. Angelia Seyfferth at the University of Delaware and supported by IAFNS Food and Chemical Safety Committee uses spinach as an example to compare and contrast how cadmium and lead differ in how they move through soil and accumulate in plant foods. The paper also discusses practical pre- and post-harvest techniques to reduce human exposure to these metals that can be adopted by farmers, food processors and consumers.

The new study, “Mitigating Toxic Metal Exposure Through Leafy Greens: A Comprehensive Review Contrasting Cadmium and Lead in Spinach,” appeared in a recent issue of the peer-reviewed journal GeoHealth.

This review highlights differences in the magnitude of exposure, bioavailability, and the practicality of mitigation strategies and calls for more research on cutting chloride inputs to leafy green crops like spinach, kale and lettuce to reduce plant uptake of cadmium. However, chloride-based disinfectants are important in reducing pathogens on crops like spinach, creating a risk-risk tradeoff that needs to be carefully managed. Some fertilizers are also chloride-based and could be substituted.

According to the authors, “It is paramount to understand the soil and plant factors that dictate contaminant accumulation in edible tissues to identify mitigation strategies for metals in foods.” They recommend action during both crop cultivation and product processing. “Pre-harvest techniques are generally actionable by the grower and include soil preparations and amendments, irrigation practices, and cultivar selection. Post-harvest techniques are further downstream and include spinach handling in the field, washing either by a factory or by the consumer, and other consumer-driven choices regarding diets.” The paper also looks at mitigation steps for lead and other metals in several crops.

The researchers conclude that “…more applied research on mitigation strategies at the field scale is warranted. Because growers require cost-effective or -neutral solutions, policy efforts should focus on incentivizing this change for growers to keep them competitive in global markets.”

According to lead author Angelia Seyfferth, “We interviewed stakeholders in the spinach sector and learned that producers are generally willing to adopt mitigation measures but would like to see more data on whether mitigation is needed and to what extent. Regulatory bodies must be mindful of increased costs to producers because they are usually operating on thin margins.” 

The study is available here. 

The Institute for the Advancement of Food and Nutrition Sciences (IAFNS) is committed to leading positive change across the food and beverage ecosystem. This paper was supported in part by IAFNS Food and Chemical Safety Committee. IAFNS is a 501(c)(3) science-focused nonprofit uniquely positioned to mobilize government, industry and academia to drive, fund and lead actionable research. iafns.org