Do the former colonizing powers, like their former colonies, have "postcolonial medicine," and if so, where does it take place, who practices it, and upon whom? How has British medicine in particular responded to the huge cultural shifts represented by the rise of the New Commonwealth and associated postcolonial immigration? I address these questions through a case study of the medical and political responses to vitamin D deficiency among Britain's South Asian communities since the 1960s. My research suggests that in these contexts, diet frequently became a proxy or shorthand for culture (and religion, and race), while disease justified pressure to assimilate.