Christiaan Eijkman (born Aug. 11, 1858, Nijkerk, Neth.—died Nov. 5, 1930, Utrecht) was a Dutch physician and pathologist whose demonstration thatberiberi is caused by poor diet led to the discovery ofvitamins. Together withSir Frederick Hopkins, he was awarded the 1929Nobel Prize for Physiology or Medicine.

Eijkman received a medical degree from the University ofAmsterdam (1883) and served as a medical officer in theDutch East Indies (1883–85). He then worked withRobert Koch inBerlin on bacteriological research and in 1886 returned toJava to investigate the cause of beriberi. In 1888 Eijkman was appointed director of the research laboratory forpathological anatomy andbacteriology and of the Javanese Medical School in Batavia (now Jakarta). Eijkman sought a bacterial cause for beriberi. In 1890polyneuritis broke out among his laboratory chickens. Noticing thisdisease’s striking resemblance to the polyneuritis occurring in beriberi, he was eventually (1897) able to show that the condition was caused by feeding the fowl a diet of polished, rather than unpolished, rice.

Eijkman believed that the polyneuritis was caused by atoxic chemical agent, possibly originating from the action of intestinal microorganisms on boiled rice. He maintained this theory even after his successor in Batavia, Gerrit Grijns, demonstrated (1901) that the problem was a nutritionaldeficiency, later determined to be a lack ofvitamin B₁ (thiamine). Eijkman returned to the Netherlands in 1896 to serve as a professor at the University ofUtrecht (1898–1928).