Peanut storage shed in rural Senegal.

The toxic imperial metabolism of Senegalese peanuts

The identification of aflatoxin in the 1960s troubled plans for Senegalese peanuts. Blamed for the acute poisoning of English poultry fed with Brazilian peanut meal, this fungal metabolite was soon found to cause liver tumours in rats – could it also be carcinogenic in humans? – and to be pervasive in hot-weather crops. One project that aflatoxin disrupted was “Farine 21,” a nutritionist-designed flour that would solve the West African “protein-gap” while recycling the residue of Senegal’s oil processing industry – the protein-rich oilcake left after extraction.[1] In early 1950s, nutritionists noted that Africa was exporting the protein that its human inhabitants were newly diagnosed as deficient in.[2] They proposed a new loop in the circuit that had been drawing over half of Senegal’s farming output, through newly installed factories (following a post-war reversal of the imperial policy of not-industrializing the colonies), towards French tables, as cooking oil, and through the oilcake-based feeding of livestock. After a decade of experiments and investments, involving French and West Africa scientific institutions, international agencies (FAO and UNICEF) and French-owned oil processing firms, Farine 21 was nearly ready for launch. The project was stalled then abandoned, when an FAO-sponsored test detected aflatoxin in Senegalese peanuts, and a UNICEF-funded field trial failed to identify an easy way of producing an aflatoxin-free crop.[3]

Attention to aflatoxin in peanuts destined for West African eating was brief; the focus soon turned to peanuts exports and exportability. The new republic’s development plans, after political independence in 1960, depended heavily on boosting peanut production and nationalizing its market to fund the state’s expansion and interventions. While aflatoxin was drawn out of oil during its industrial extraction, it was thereby concentrated in the oilcake. European regulation of aflatoxin in feed, as well as in the higher-value trade in “edible” peanuts that Senegal hoped to invest in, was evoked as early as 1963, as a group of expat scientists lobbied the government to fund research that would save its economy.[4] By the turn of the 1970s, imminent standards were announced by the European community, provoking a “shock” and a burst of research that Marie-Thérèse Basse, director of Senegal’s Institut de Technologie Alimentaire (ITA) and the first Senegalese woman to be certified as a biomedical doctor, complained was exclusively aimed at generating a “product … acceptable to the European market.” This research had turned away from the development of agronomic control methods, by which Senegal’s whole harvest might be made safer for eating, towards methods she called “technological,” such as sorting, which she worried would produce a good lot for export and a contaminated one “that would be consumed locally.” [5] Years earlier, the nutrition researcher J. Toury warned that Senegalese peanut-eating was already residual to the export trade in ways that amplified local exposures. The surveys he conducted, thanks to FAO-sponsored training, showed that “restes-à-terre” [literally, remain-in-ground] – pods that stayed stuck in soil when plants were pulled during the main harvest – contained high concentrations of aflatoxin. These, he told the audience of the annual meeting of the Dakar Faculty of Medicine, were the peanuts that farming families usually kept for their own consumption. Thus, Toury warned, “recent discoveries on mycotoxins will be soon called to pose a significant public health problem.”[6]

These three moments call attention – via aflatoxin detection and the stakes of its control – to how Senegalese peanut-eating has long been entangled with, and residual to, the farming and sale of peanuts-for-export. Farine 21 planned to shift how nutrients flowed through peanuts, from Senegalese labour and soil, into human or (b)ovine, European or West African bodies. Critics had, in the postwar years, accused Senegal’s peanut economy of depleting local soils, displacing subsistence farming, and creating dependence on imported food.[7] Farine 21 would not radically rebalance these nutrient circuits, but promised to redirect – albeit still through French-owned industrial waste and profit – some protein towards West African growth and vigour. Toury’s aflatoxin survey revealed that the peanuts Senegalese were already eating were contaminated by being left over after harvesting for export-sales. The threat to Senegalese health he anticipated that aflatoxin research would reveal was, Basse complained several years later, ignored as research efforts turned to maintaining the exportability of Senegalese peanuts – efforts she worried would shunt contaminated kernels back into Senegalese diets and bodies.

Disused SONACOS oil processing factory in Dakar
Disused SONACOS oil processing factory in Dakar. Photo credit Moussa Mbaye Gueye

In this essay, I take up these invitations to view aflatoxin as part of metabolic relations that were formed as Senegalese peanuts move across space, into and out of labouring soils and bodies, via factories, laboratories, and kitchens. Inspired by Alf Hornborg’s formulation of “imperial metabolism,”[8] I sketch out some of the temporal and spatial scales in which we might locate the energetic and nutrient transfers – and potential release of toxicity – attendant to the growing, processing, and eating of Senegalese peanuts. This takes us beyond agronomists’ focus on fungal-plant metabolisms, nutritionists’ interest in protein-deficient ones, or economists’ calculation of the losses incurred by trade regulation: the separated scales at which aflatoxin is usually problematized. Metabolic thinking, I hope, will bring into view the co-constitutive economic, ecological, and embodied exchanges through which peanuts absorb, carry and release energy, nutrients and perhaps toxins across land, bodies, and borders.

I cannot give a finely detailed, much less quantitative, description of these commercial-toxic-nutritional flows here. This is not only beyond the scope of my essay; it is also precluded by gaps in information, notably on Senegalese peanut-eating and aflatoxin exposure that were produced in the wake of efforts to manage aflatoxin’s threat to the value and safety of exported peanuts. I want instead to suggest ways in which we can draw into a common frame the various metabolizations of Senegalese peanuts, from fungus feeding on kernels and the gleaning and eating of restes-à-terre in Senegal to the European consumption of milk from oilcake-fed cows. This draws attention to how Senegalese peanut-eating, as both an energizing and potentially toxifying act, has long happened within imperial/global scales of trade. The stakes and qualities of this consumption have been actively shaped – but also neglected and obscured – by investments in an export-oriented peanut economy. I am particularly interested in how the colonial configuration of this economy had durable effects, into the post-independence decades, on how aflatoxin was known, controlled, and consumed after it emerged as an identifiable and risky molecule in the 1960s. 

Imperial Metabolism

Hornborg proposes “imperial metabolism” as a framework for thinking about, as he puts it in a chapter subtitle, “empire as a process of ecologically unequal exchange.”[9] Political expansion and domination enable the appropriation of land and labour in ways that redistribute ‘natural’ resources – notably energy – to the net benefit of imperial centres. This concept resonates with critical analyses of the Senegalese peanut trade. From the 1930s, observers noted that the increase in land being turned over to farming peanuts for cash was leading to deforestation and a neglect of fallowing, thus eroding soil fertility. This incipient “ecological critique” of the colonial economy was fleshed out by agronomists advocating for policies of soil conservation, in response to French metropolitan pressures to boost peanut production to fill an oilseed supply gap at the end of World War II.[10] Later, the economist Bernard Founou-Tchuigoua integrated these critics’ diagnoses of soil depletion into a Marxian frame, in which he set the price paid to farmers for peanuts against the real cost of maintaining Senegalese (re)productive capacities, and as a product of French political and industrial interests in keeping the price of cooking oil low.[11] He argued that the underpayment of Senegalese peanuts was compensated by farmers’ own labour and land investment in feeding themselves by growing millet, while gradually using up the “capital” of soil fertility: a “super-exploitation” of both “men (sic.)” and of “nature.” Agronomists had, in the 1950s, proposed ways of replenishing this “soil capital,” but Founou-Tchuigoua concludes that they were rejected by the administration due to being “incompatible with the underlying strategy [of the colonial peanut economy], based on the minimisation of fixed capital and the extraction of ‘sufficient’ profit rates for the oil industry.”[12] Cast in Marxist terms, Founou-Tchuigoua’s analysis can also be seen as a metabolic one, demonstrating how nutrient intakes and outputs of peanuts and millet, soil ecologies and labouring bodies – French and Senegalese – were harnessed to maintain advantages for French firms and administrations determined to reinvest as little as possible into production.

Like the researchers on whose work he draws, Founou-Tchuigoua theorises peanuts mainly as a cash crop, drawing energy away from Senegal, and subsistence crops (chiefly millet) and imported foods (chiefly rice) as the main metabolic inputs. He nonetheless offers some clues as to how Senegalese peanut-eating was entangled in these uneven imperial metabolic exchanges. Citing the influential Mission Portères report of 1951, he notes that Senegalese domestic consumption of peanuts – for eating and as seed stock – had grown steadily in both absolute terms and as a proportion of the harvest since the beginning of the century. Yet this consumption, he points out, had developed at the margins of the colonial export economy, particularly following the prohibition of small-scale oil pressing in the early 1930s, when a sharp drop in world prices prompted Senegalese farmers to eat their harvest and seed stocks instead of selling them. Founou-Tchuigoua quotes the merchant Assane Diop’s statement to a 1949 economic conference, condemning this prohibition as unjust given farmers’ calculation they could get more nutritional and monetary value from crushing their own peanuts than from selling them to oil factories.[13] Thus, while Senegalese peanut-eating grew alongside the expansion of cash-cropping, French administrative and commercial demands and interventions, prioritising sale-for-export, put constraints on which peanuts could be eaten and how. 

Peanut storage shed in rural Senegal.
Peanut storage shed in rural Senegal. Photo credit: Noémi Tousignant

Eating Residue

Founou-Tchuigoua’s observations on the prohibition of artisanal oil-crushing join Toury’s warnings about “restes-à-terre” and Basse’s concerns about control-for-export in highlighting the residuality of Senegalese peanut-eating within an export-oriented agricultural economy. By the mid-1980s, Senegalese were growing fewer peanuts under farming and trading conditions destabilised by drought, the withdrawal of state support, and global market prices. Oil factories, run by a nationalized firm since 1975, were undersupplied. To break even, the firm imported and refined cheaper cooking oils for the Senegalese market, saving higher-quality peanut oil for export.[14] A growing share of the harvest may have been traded within Senegal, in the so-called “parallel” market (but legalised in 1988). In his PhD thesis, Matar Gaye describes a thriving local (so-called “artisanal”) industry processing and selling peanut oil, paste and flour in the mid-1990s.[15] Formally illegal until 2010, this sector initially took off, Gaye found, in towns under Sufi religious authority and was increasingly tolerated by the state as it grew after peanut markets were liberalised in the mid-1980s. A decade later, shops in some areas sold more of this oil than the imported refined oils that Senegalese “homemakers,” Gaye notes mildly, “do not prefer.”

Gaye also observed that the women running this sector could only turn a profit by processing the cheapest peanuts: the damaged kernels sorted out during shelling, called sax-sax. Earlier research had found that broken kernels were likely to be much more contaminated than intact ones. Some Senegalese cooks’ preference for peanut oil, which was sometimes cheaper, always tastier and better suited to high-heat cooking methods than imported vegetable oil, suggests that the latter was the residual product, dumped on the margins of the global market. This has made the potential toxicity of unrefined peanut oil a politically delicate matter in Senegal, a French agronomist told me. Rural businesswomen and cooks, I also heard, suspect that the state and oil industry overemphasize this hazard to limit access to “their own” peanuts, reminiscent of colonial prohibitions.

Senegalese-eaten peanuts are not always or merely the toxic leftovers of an export economy. And yet, even as they are valued for their taste, domestic marketability, high smoke point and contribution to food sovereignty, these peanuts still occupy a space that is deeply marked by ongoing histories of imperial/global metabolic exchange. It is in this space that the carcinogenicity of peanuts has been embodied by Senegalese eaters and warned against by experts such as Basse and Toury, but also often dismissed, by farmers, traders, politicians and other experts, as a myth or an exaggeration, meant to block their export or to secure their supply for industrial processing.


A 1990 headline in Senegal’s pro-government newspaper, Le Soleil, proclaimed “aflatoxin conquered.”[16] In 1981, the firm, SONACOS, implemented an innovative ammonia-based detoxification method: “a veritable prowess of the Senegalese, the only ones to have this process.”[17] Feed standards were fixed in 1976, but the detection of aflatoxin in French milk in 1981 – traced to oilcake from a highly contaminated drought-year Senegalese harvest – revealed lax implementation. French coverage worried about children being fed carcinogenic milk and reported the demands of dairy professionals to ban peanut-cake imports, as well as other farmers’ plea to maintain access to this cheap source of protein.[18]

Detoxification, coupled with regulatory tightening, saved Senegal’s oilcake market. Or so claimed the head of SONACOS, reported by Le Soleil in 1992 under the headline “ammonia, a necessary evil.”[19] Days after a deadly ammonia tanker explosion at the Dakar oil factory, he defended detoxification, without which there would be “no [Senegalese] peanut economy…peanuts would have no value.”[20] Critical journalists, calling the carcinogenicity of aflatoxin into doubt, charged that Senegalese lives and livelihoods had been sacrificed in a meaningless performance of European safety. One headline ran “75 dead for safe peanuts,” while Tidiane Kasse commented acidly that SONACOS had worked harder to meet “the technical standards required to ensure the health of European community cattle” than to protect “the safety of its [own] workers.”[21]

Oilcake detoxification was pursued as an alternative to “agronomic” farm-level control strategies. Early agronomic research had meticulously documented how aflatoxin concentration changed in relation to factors such as weather patterns, insect damage, planting and harvesting timings, and ways of picking, stacking, and threshing. As state-run farmer outreach expanded in the early 1970s, aflatoxin researchers presented the ministries of planning and of rural development with an ambitious program to encourage farmers – through education and higher prices – to grow, dry, and sell a less contaminated, higher-quality crop.[22] The proposal was ranked as low priority.[23] Detoxification was cheaper and could circumvent the fickleness of weather, farmers and fungal metabolisms.[24]

Detoxification was deadly because it turned out, with the ammonia tanker explosion, to be catastrophically unsafe for Senegalese factory workers and bystanders. But it may have also killed more “slowly” by separating aflatoxin control from Senegalese farming and eating. This allowed exposures that, by the turn of the 1990s and increasingly thereafter, were widely deemed carcinogenic; especially when combined with chronic hepatitis B infection, also a risk factor of liver cancer, and known to be highly prevalent in Senegal since the 1970s. Some, in response to the SONACOS tragedy, questioned this carcinogenicity, evoking a relation between the overprotection of European cattle and milk-drinkers and the ammonia exposure of Senegalese workers. But if we side with evidence that Senegalese peanuts were and are carcinogenic – but, in Senegal, not worth considering as such – this also brings into view Senegalese bodies that farm, eat peanuts, and carry viruses, as well as soils as fungal and crop habitats, as potential but bypassed loci of toxicity, protection and care.  

Recall how Founou-Tchuigoua argues that measures of care for Senegalese soil fertility were, in the 1950s, deemed incompatible with the need to maintain a French supply of cooking oil that was both cheap and profitable enough. This history of underinvestment in the conditions of peanut/farmer (re)production also, in the early 1970s, made the farmer outreach program a hard sell. Detoxifying oilcake made the quality of Senegalese farming irrelevant to peanuts’ exportability, within an architecture of trade and regulation, with its colonial roots and postcolonial stakes, oriented towards the feeding and protection of European bodies. Persistent Senegalese exposures to aflatoxin appear, in this view, as the cost of eating on the margins of imperial/global metabolism.

[1] Henri Dupin, “Propositions pour une étude sur les possibilités de diffusion et de commercialisation de la farine d’arachide propre à l’alimentation humaine,” ORANA. Unpublished report, dated June 1960, likely submitted to the Government of Senegal, held at the National Library of Senegal (call number po III 4° 797).  

[2] John Nott, ““No one may starve in the British Empire”: kwashiorkor, protein and the politics of nutrition between Britain and Africa,” Social History of Medicine 34, 2 (2021): 553-576.

[3] Pierre Goarin, Jacques Toury, et al., “Rapport au Gouvernement du Sénégal sur les contaminations de l’arachide par aspergillus flavus, les études en cours et les études à réaliser,” unpublished document, circa 1964, held at the National Library of Senegal (call number Bi III 4° 2802).

[4] Ibid. 

[5] A. J. Tuyns, « Report on a visit to Dakar, 21-25 February 1971,” Box J1, Folder L4/3 Dakar, Archives of the International Centre for Research on Cancer (IARC), Lyons, France. Tuyns is a cancer epidemiologist looking to set up IARC-sponsored studies of aflatoxin and liver cancer in Senegal.

[6] Jacques Toury, “Communication faite aux Journées Médicales de Dakar, 4-10 janvier 1964, » Unpublished document held in the collections of the Organisation de Recherche sur l’Alimentation et la Nutrition Africaine (ORANA).

[7] Bernard Founou-Tchuigoua, Fondements de l’économie de traite au Sénégal (La surexploitation d’une colonie de 1880 à 1960), Senegal : Panafrika/Silex/Nouvelles du Sud en coédition avec NENA, 2016 [1981]. 

[8] Alf Hornborg, “Imperial Metabolism,” In Peter Fibiger Bang, C. A. Bayly and Walter Schedel (eds.) The Oxford World History of Empire (2021): 437-459.

[9] Hornborg, « Imperial Metabolism. »

[10] Céline Pessis, “Les sols sénégalais malades de l’arachide, 1944-1952.” Monde (s). Histoire, Espaces, Relations (2013): 127-144.

[11] Founou Tchuigoua, Les fondements de l’économie.

[12] Ibid, chapter IV.

[13] Ibid, chapter II.

[14] Claude Freud, Ellen Hanak Freud, Jacques Richard and Pierre Thénevin, L’arachide au Sénégal: un moteur en panne. KARTHALA Editions, 1997.

[15] Matar Gaye, “Les politiques d’ajustement dans le secteur agricole sénégalais : analyse critique des implications sur la filière arachidière » Doctoral thesis, Univresity of Leuven, 1998.

[16] Cited in Pierre Barrot, « Soixante-quinze morts pour une arachide saine, » Syfia news agency, 1 April 1992.

[17] Ibid.

[18] « Dossier « Aflatoxines » printemps 1981, » press cuttings from French newspapers, march-june 1981, Agriculture; Cabinet et services rattachés; Sous-direction de l’information; Bureau gestion, information (1979-1984), côte 19850125/60, Archives Nationales de France (Pierrefitte-sur-Seine), 

[19] Abdallah Faye, “Filière arachidière. L’ammoniac, un mal nécessaire déclare Abdoulaye Diop; Pas de filière arachide sans traitement à l’ammoniac,” Le Soleil, 27 March 1992: p. 1 and 8.

[20] Ibid, p.8.

[21] Tidiane Kasse, « Frapper haut, frapper fort »  Wal Fadjiri, 27 March-2 April: p.4; Barrot 1992.

[22] Anonymous (1973). Moyens à mettre en oeuvre pour l’exécution d’un projet de vulgarisation sur la prévention de l’aflatoxine de l’arachide au Sénégal. Campagne agricole 1973/74. Document A61-33, Centre de Documentation de l’ISRA, Dakar.

[23] Ibid (loose letter kept in copy of report).

[24] James Pattinson and J. Deuse  « Les problèmes de stockage de grains au Sénégal et les mesures entreprises et proposées pour leurs résolutions, FAO and ITA. » 1970. Unpublished report held in National Library of Senegal, call number Po III 4° 2282.

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