Antivitamins

Antinutritional factors that destroy vitamins or block their metabolic action. The textbook examples: thiaminase, the anti-vitamin B1 enzyme in raw fish and some shellfish that cleaves thiamin; certain caramel colorants with anti-vitamin B6 activity; and dicoumarol, the anti-vitamin K compound that forms in spoiled sweet clover and caused cattle haemorrhages before its anticoagulant mechanism was understood. They matter most where raw or minimally processed foods dominate — populations eating large amounts of raw fish have historically faced thiamin deficiency. Cooking destroys thiaminase, which is why the risk tracks raw consumption.