Nutrients and non-essential metals in darkibor kale grown at urban and rural farms

Authors: KIM, BRENT - Johns Hopkins School Of Public Health; LUPOLT, SARAH - Johns Hopkins School Of Public Health; SANTO, RAYCHEL - Johns Hopkins School Of Public Health; BACHMAN, GRACE - Johns Hopkins School Of Public Health; ZHU, XUDONG - Orise Fellow; Yang, Tianbao; Fukagawa, Naomi; RICHARDSON, MATTHEW - University Of District Of Columbia; Green, Carrie; PHILLIPS, KATHERINE - Virginia Tech; NACHMAN, KEEVE - Johns Hopkins School Of Public Health

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2023
Publication Date: 4/16/2024
Citation: Kim, B.F., Lupolt, S.N., Santo, R.E., Bachman, G., Zhu, X., Yang, T., Fukagawa, N.K., Richardson, M.L., Green, C.E., Phillips, K.M., Nachman, K.E. 2024. Nutrients and non-essential metals in darkibor kale grown at urban and rural farms. PLOS ONE. 19(4). https://doi.org/10.1371/journal.pone.0296840.
DOI: https://doi.org/10.1371/journal.pone.0296840

Interpretive Summary: Kale is a nutrient-dense leafy vegetable associated with wide-ranging health benefits. It is tolerant of drought and temperature fluctuations, and could thus serve an increasingly important role in providing a safe and nutritious food supply during the climate crisis, and kale’s ease of cultivation and ability to be grown in a wide range of soils make it a good fit for urban agriculture. In this pilot study we explored potential differences in nutritional elements, non-essential metals, and select health-relevant nutrients in Darkibor kale grown at urban versus rural farms. Although sample sizes were small, we identified potentially meaningful differences in concentrations of several components between urban and rural kale samples. Concentrations of elements were generally higher in kale from urban farms; carotenoids and vitamins were generally higher in kale from rural farms. Some urban-rural differences were more pronounced than those identified in prior research, although for some elements, variation within urban and rural farms was greater than variation between urban and rural farms. Metals concentrations in all kale samples remained below public health guidelines for lead and cadmium. For some nutrients, mean concentrations were higher than upper ranges reported in prior estimates. The nutritive and metals composition of this important crop, and the factors that influence it, merit continued investigation given its growing popularity.

Technical Abstract: Kale is a nutrient-dense leafy vegetable associated with wide-ranging health benefits. It is tolerant of drought and temperature fluctuations, and could thus serve an increasingly important role in providing a safe and nutritious food supply during the climate crisis, while kale’s ease of cultivation and ability to be grown in a wide range of soils make it a good fit for urban agriculture. In this pilot study we explored potential differences in nutritional elements, non-essential metals, and select health-relevant nutrients in Darkibor kale grown at urban versus rural farms. Although sample sizes were small, we identified potentially meaningful differences in concentrations of several components between urban and rural kale samples. Concentrations of elements were generally higher in kale from urban farms; carotenoids and vitamins were generally higher in kale from rural farms. Some urban-rural differences were more pronounced than those identified in prior research, although for some elements, variance within urban and rural farms was greater than variance between urban and rural farms. Metals concentrations in all kale samples remained below public health guidelines for lead and cadmium. For some nutrients, mean concentrations were higher than upper ranges reported in prior estimates. The nutritive and metals composition of this important crop, and the factors that influence it, merit continued investigation given its growing popularity.