Increased concentrations of atmospheric carbon dioxide and zinc deficiency
Authors: Brian Thompson, Marc J Cohen
Journal: The Lancet Global Health (2015)

Inadequate dietary zinc contributes to stunting in young children, which WHO identifies as “one of the most significant impediments to human development”.1WHOGlobal nutrition targets 2025: stunting policy brief. World Health Organization, Geneva2014http://apps.who.int/iris/bitstream/10665/149019/1/WHO_NMH_NHD_14.3_eng.pdfGoogle Scholar Stunting's long-term effects include “diminished cognitive and physical development, reduced productive capacity and poor health, and an increased risk of degenerative diseases such as diabetes”.1WHOGlobal nutrition targets 2025: stunting policy brief. World Health Organization, Geneva2014http://apps.who.int/iris/bitstream/10665/149019/1/WHO_NMH_NHD_14.3_eng.pdfGoogle Scholar In The Lancet Global Health, Samuel Myers and colleagues2Myers SS Wessells KR Kloog I Zanobetti A Schwartz J Effect of increased concentrations of atmospheric carbon dioxide on the global threat of zinc deficiency: a modelling study.Lancet Glob Health. 2015; 3: e639-e645Summary Full Text Full Text PDF Scopus (97) Google Scholar estimate that 138 million additional people will be at risk of zinc deficiency in 2050 on the assumption that elevated atmospheric carbon dioxide (CO2) concentrations lower the zinc content of key food crops. The paper postulates that the biggest increases in zinc deficiency will occur in regions where the contribution of staple crops to the diet is highest—south Asia and sub-Saharan Africa; these regions currently have the world's highest prevalence of stunting.3UNICEFThe state of the world's children 2015: executive summary. UNICEF, New York2015http://www.unicef.org/publications/files/SOWC_2015_Summary_and_Tables.pdfGoogle Scholar Myers and colleagues point out that, whereas wealthier people will be responsible for most of the projected increases in CO2 emissions, people with lower incomes will bear the brunt of the resulting zinc deficiency, making this an issue of social justice. The study makes an important contribution to our knowledge of the effects of climate change on human nutrition. However, we do find that certain aspects are problematic. First, Myers and colleagues indicate that there is evidence that elevated CO2 concentrations will also mean reduced iron and protein content in key food crops. The paper's single-nutrient focus and policy recommendations are not in keeping with current best practice. The 2014 Rome Declaration on Nutrition, endorsed at the Second International Conference on Nutrition, summarises this ethos, calling for a holistic approach to “the elimination of malnutrition in all its forms”, with “nutrition policies [that] promote a diversified, balanced, and healthy diet at all stages of life”.1WHOGlobal nutrition targets 2025: stunting policy brief. World Health Organization, Geneva2014http://apps.who.int/iris/bitstream/10665/149019/1/WHO_NMH_NHD_14.3_eng.pdfGoogle Scholar, 4FAO and WHORome declaration on nutrition. FAO, Rome2014http://www.fao.org/3/a-ml542e.pdfGoogle Scholar Second, despite the paper's emphasis on social justice, its policy recommendations (zinc supplementation, fortification of staple foods, application of zinc-containing fertilisers to food crops, biofortification of staple crops, and cross-breeding of staples with varieties with less nutritional sensitivity to rising CO2 levels) are all top-down in nature. A rights-based approach to addressing the effect of climate change on food security and nutrition would also focus on empowering poor farmers and food consumers to improve their own nutrition and make informed choices about combatting malnutrition. It would include community-based promotion of good nutrition, balanced diets, and healthy practices.5Thompson B Cohen MJ The impact of climate change and bioenergy on nutrition. Springer for FAO, Dordrecht2012Crossref Scopus (16) Google Scholar Third, Myers and colleagues assert that “Anticipating how the global diet is likely to change over the coming decades is difficult.” However, several studies have examined various scenarios of future food consumption,6Msangi S Rosegrant MW Feeding the future's changing diets: implications for agriculture markets, nutrition, and policy. International Food Policy Research Institute, Washington, DC2011Google Scholar, 7ForesightThe future of food and farming. Government Office for Science, London2011https://www.gov.uk/government/publications/future-of-food-and-farmingGoogle Scholar, 8Alexandratos N Bruinsma J World agriculture towards 2030/2050: the 2012 revision. ESA working paper 12-03. FAO, Rome2012http://www.fao.org/economic/esa/publications/details/en/c/147899/Google Scholar, 9OECD and FAOOECD-FAO Agricultural Outlook 2015-2024. Organisation for Economic Co-operation and Development, Paris2015http://www.oecd-ilibrary.org/agriculture-and-food/oecd-fao-agricultural-outlook-2015_agr_outlook-2015-enCrossref Google Scholar and the paper's failure to engage with this literature is a noticeable shortcoming. Related to this oversight, the paper bases its conclusions on a dietary model that remains unchanged with respect to calories and composition, an assumption Myers and colleagues acknowledge as being simplistic, and despite the above-mentioned studies, which indicate that future dietary composition is likely to involve a reduction in staples and increases in vegetable oils and animal-sourced foods which are expected to increase zinc intake. Furthermore, the paper does not take population growth or urbanisation into consideration, despite the considerable evidence that these factors will have a considerable bearing on the composition and quality of diets, including the adequacy of zinc and other micronutrient intakes.10Cohen MJ Garrett JL The food price crisis and urban food (in)security.Environ Urban. 2010; 22: 467-482Crossref Scopus (137) Google Scholar Additionally, the paper suggests in passing that economic growth might improve the quality of diets, but does not explore this point adequately. Finally, the data used in the paper are not disaggregated below the national level, between urban and rural regions, or between males and females. Myers and colleagues obviously could not control this problem, but further research should explore whether there are substantial within-country, urban–rural, or gender differences in growing vulnerability to malnutrition. In summary, the paper grapples with key public health issues and pressing matters that global policy makers need to address. As we have argued elsewhere, agriculture, food security, and nutrition need to have a high place on the agenda of policy discussions about climate change and sustainable development.5Thompson B Cohen MJ The impact of climate change and bioenergy on nutrition. Springer for FAO, Dordrecht2012Crossref Scopus (16) Google Scholar The high-level meetings on these topics in New York and Paris later this year need to address the effects of a changing climate on nutrition and the implications for development. We declare no competing interests. Effect of increased concentrations of atmospheric carbon dioxide on the global threat of zinc deficiency: a modelling studyOur results indicate that one heretofore unquantified human health effect associated with anthropogenic CO2 emissions will be a significant increase in the human population at risk of zinc deficiency. Our country-specific findings can be used to help guide interventions aimed at reducing this vulnerability. Full-Text PDF Open Access