Working in the Dutch East Indies (now Indonesia), Eijkman linked the widespread disease beriberi to the consumption of polished rice. He transformed field observations in prisons and the army into controlled chicken experiments, showing that a mysterious substance in the rice hulls prevented peripheral nerve inflammation. He called it the “antineuritic factor.” The work proved that specific nutrient deficiencies cause disease, shaping public-health nutrition policies and the development of vitamin-fortified foods.

Vitamin B1 (thiamine) functions as the co-enzyme TPP in carbohydrate metabolism, facilitating decarboxylation reactions in complexes such as pyruvate dehydrogenase. Eijkman’s chicken beriberi model became the first quantitative bioassay for a micronutrient. Subsequent work by Funk coined the term “vitamine,” and Williams determined thiamine’s chemical structure. Today vitamin B1 is routinely added to polished rice and wheat flour and is used clinically to treat metabolic acidosis and Wernicke’s encephalopathy.

Using the chicken beriberi model, Eijkman correlated peripheral nerve degeneration with impaired ATP production and suggested accumulation of keto-acids on refined-carbohydrate diets. The antineuritic factor was later identified as thiamine, phosphorylated via the HMP-P pathway to TPP. Inhibition of TPP-dependent enzymes perturbs the NADH/NAD+ ratio at the distal glycolytic step and activates apoptotic cascades, as verified in modern animal models. Eijkman’s findings paved the way for molecular studies on mitochondrial metabolic disorders and neurodegeneration.