A number of chemicals or enzymes may destroy or degrade thiamine (vitamin B1). These antithiamine compounds can result in thiamine deficiency in a person with limited thiamine intake.
Mechanism of action:
(1) thiaminase enzymatic activity
(2) antagonists (polyphenol, flaonoids, hemin)
Sources of antithiamine compounds:
(1) raw or fermented fish (thiaminase)
(2) shellfish (thiaminase)
(3) ferns (thiaminase)
(4) bacterial contamination (thiaminase)
(5) tea or coffee (polyphenols)
(6) betel nut (polyphenol)
(7) vegetables such as red cabbage, brussel sprouts or red beets (polyphenols)
(8) berries such as blueberries or red currants (polyphenols)
(9) certain fruits and vegetables containing flavonoids
(10) red meat (haemin)
Thiaminase can be inactivated by heating.
Other conditions that can degrade thiamine (but usually not listed as antithiamine factors):
(1) prolonged heating of food containing thiamine
(2) sulphites and bisulphites
(3) oxidizing and reducing agents (copper ion)
(4) chlorine, including chlorinated water
(5) alkaline pH, including treating food with lime
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