What lessons about the microbiome can we learn from considering the history of using growth promoters in food for livestock? This was the theme of Hannah Landecker's talk and workshop with the OxIMP network, the second in this term's seminar series.
In Wednesday's session the focus was on the 'food of our food'. Through linking together stories around human metabolic processes and animal feed, Hannah raised a number of key themes pertinent to the social implications of the microbiome. These included shifting from linear to systemic modes of thinking, shifting from considering things to considering processes, 'thinking chemically', and developing the concept of the anthropocene at a cellular scale.
The first part of the talk considered the metabolic processes through which humans cope with toxic compounds in the environment. Hannah explained in some detail the links between the metabolism of both foods and toxins, and how the latter links to chromosomal instability - and thus also to various diseases. She gave the example of arsenical compounds in the environment being linked to diabetes through the effect they have on genome instability.
The second part turned to the history of using growth promoters in animal feed - largely antimicrobial or antibiotic compounds, and with a history that pre-dates the antibiotic era. In the 1930s farm animals were, in the US, increasingly conceptualised as machines made of food. The agricultural logics centred around input/output ratios - how much food was required to produce how much meat. Growth promoters were seen as a way to improve efficiency, with little regard to their possible wider impacts. Various derivatives of arsenic were among the 'magic bullet' precursors to antibiotics, and became important in agriculture. They were found to be very good at controlling intestinal parasites in chicken - but also had growth promoting qualities.
The two parts of the talk started to draw together as Hannah discussed the emerging links between the historical use of these arsenical compounds, and contemporary human health. She cited a 2012 US Consumer Reports study that showed babyfood sweetened with brown rice syrup had high levels of arsenic. One pathway: historical chicken feed had incorporated arsenical compounds as a growth promoter; waste from these chickens had been used as a fertiliser in rice production (arsenical compounds in pesticides are also implicated).
The last section of Hannah's talk drew these two stories together, by making links between arsenic and the microbiome. The microbiome metabolises arsenic too. Arsenical exposures in the microbiome change population structures of bacteria and thus also the production ratios of metabolites. They also lead to antimicrobial resistance. So there are microbiome mediated effects on human health - the final irony in this tale is that a western diet has been shown in mouse models to accentuate the injurious effects of arsenic - i.e. the substance has a stronger deleterious impact in the context of the dietary systems that it makes possible. As Hannah put it, 'nurture metabolises nature'.
The OxIMP network would like to thank Hannah for her time, company and insight.
Hannah Landecker is a sociologist at UCLA and the Director of the Institute for Society and Genetics. She has written previously on the history of antibiotic use and the development of antibiotic resistance, and is currently working on a book provisionally titled 'American Metabolism'. The book aims to explore recent developments in the metabolic sciences and their various social implications.