Can Nutritional Benefit be Considered Quantitatively When Advising Urban Gardeners Which Vegetables to Grow to Reduce Risks of Lead (Pb) Exposure?

BACKGROUND: Foods differ with respect to their nutritional content (and associated health benefits), and also in their tendency to contain potentially harmful chemical contaminants. For example, fish differ in their omega-3 fatty acid content and associated cardiovascular benefits and also in their tendency to contain mercury. Information about these relative differences in benefits and risks is published by federal agencies (DHHS, FDA, EPA, DA) to help the public make informed choices. Vegetables also contain nutrients that are important for good health, and the public is encouraged to eat vegetables. This message can be particularly important in some urban neighborhoods with poor access to fresh produce and high incidence of chronic diseases. However, vegetables grown in these same urban neighborhoods may harbor chemical contaminants (e.g., lead). Lead levels in some vegetables tend to be higher than others regardless of the lead levels in soil. As a result, gardeners in urban areas are encouraged to grow vegetables lower in lead (fruiting vegetables) over others (leafy and root vegetables). This advice does not consider relative differences in nutritional value of vegetables and associated health benefits, which could be an important consideration in these communities. In the current study, we explore the feasibility of considering nutrient content of vegetables to refine advice given to urban gardeners to minimize exposure to lead.

METHODS: We combined an existing lead dataset with available nutrient data sets (e.g., for anti-oxidant content), matching by common vegetable name and categorizing by vegetable type (e.g., fruiting vegetables). We calculated individual vegetable means, stratified by the median for all vegetables and examined data by quadrants (lower and higher lead and nutrients) for each nutrient.

RESULTS: We found that levels of lead and certain nutrients differ significantly by vegetable type. Also, while nearly all fruiting vegetables have lower levels of lead, fruits differ significantly with respect to content of some nutrients, suggesting the potential benefit of fine-tuning recommendations to consider growing those which are lowest in lead and highest in nutrient content (e.g., green beans, broccoli). Conversely, some vegetables that have higher levels of lead have particularly low levels of nutrients, and gardeners could consider not growing these vegetables.

CONCLUSIONS: Our preliminary analysis suggests that consideration of nutrient content could inform some outreach strategies for urban gardeners. However, a more comprehensive analysis incorporating a bigger lead data set and more nutrient data would be needed to confirm results.