From Disorder to Distinction: Lactose Intolerance and the Racialization of Digestion in Postwar Medicine (1950–1980)

Abstract This article examines how scientific research on lactose digestion from 1950 to 1980 became entangled in shifting discourses on race, heredity, and population. It traces how scientific framings of lactose digestion changed during this period—initially racialized as a disorder (lactase deficiency) affecting Black Americans, later reclassified as an ethnic trait, and ultimately reinterpreted as a biomarker of European ancestry. Drawing on medical research on “lactose science” and archival sources, this study explores how geneticists, medical researchers, and anthropologists jointly navigated the complexities of race and human variation in the postwar period. Using Peter Galison’s concept of trading zones , the paper traces how ethnicity and population emerged as strategic alternatives to race, facilitating interdisciplinary collaboration while preserving racialized assumptions about biological difference. The paper argues that despite efforts to align with UNESCO’s post-racial scientific agenda, research on lactose digestion came to produce a normative discourse around whiteness. In doing so, it raises a critical question: how did an ostensibly anti-racist science inadvertently revive older racial biologisms?