Eijkman produced beriberi experimentally in fowls; from this he was led to conclude that a diet of over-milled rice was the chief cause, both in fowls and humans. Thus his work was of great importance in determining the aetiology of beriberi, and he further had the distinction of being the first to produce experimentally a disease of dietary deficiency origin. German translation in Virchows Arch. path. Anat., 1897, 148, 523-32.

In 1929 Eijman shared the Nobel Prize in Physiology or Medicine with F. G. Hopkins "for discovery of the antineuritic vitamin."