Lecture 8- Thiamin Flashcards
food sources of thiamin
wholegrains,
pork (also other meats)
potatoes and their skin
what is enrichment
when you add in the nutrient to make up for some kind of processing that removed the nutrient
what is fortification
adding the nutrient to food that lots of people eat
3 examples of food related thiamin losses
1- refining grains
2- thiamin antagonists
3- thiaminases = enzymes that act on thiamin
how does refining grains result in thiamin losses
going from something like wholegrain down to brown down to white flour or bread etc
this removes thiamin, but improves shelf life as the embryo germ is removed
what are 3 thiamin antagonists and what are they found in
sulfites (preserve the colour of meat)
cyanogenic glycosides (in cassava)
tannins (tea, coffee, betel nuts)
how do tannins make thiamin less bioavailable
they will oxidise thiamin, making it less easy for your body to absorb
what are thiaminases
enzymes that act on thiamin
how can thiaminases cause thiamin losses
plants such as bracken fern
some kaimoana such as carp, mussels
some insects including African silk worm larvae
where is betel nut chewing an important practice
in South and South-East Asia, Asia Pacific
what is betel nut chewing considered
a stimulant drug, addictive
(one portion has the effect of about 6 cups of coffee)
what are the long term impacts of betel nut chewing
discolouration of teeth and gums, mouth ulcers and oral cancers
what is the chemical structure of thiamin
colourless organosulfur compound
is thiamin water soluble or water insoluble
water soluble
when is thiamin stable
when in acid solution and when frozen
when is thiamin unstable
unstable to heat, UV light and alkali
what are 3 of the 5 phosphorylated forms of thiamin (one of them has two names)
thiamin monophosphate (TMP)
thiamin diphosphate also known as thamin pyrophosphate (TPP)
thiamin triphosphate (TTP)
all forms of thiamin can be interconverted in tissues but what is the distribution of these usually
80% is TPP
5-10% is TTP
remainder TMP, free thiamin
how is thiamin converted to thiamin pyrophosphate
thiamin diphosphotransferase converted thiamin to its active form (TPP) via TMP
so converts it to thiamin monophosphate first and then thiamin pyrophosphate
where is thiamin absorbed
mainly in the jejunum and ileum
what are the two forms of thiamin absorption and when do they usually happen
active carried mediated process at low concentrations
passive diffusion at high concentrations (more at supplement level)
what is the bioavailability of thiamin
little information
absorption can be inhibited by alcohol consumption
absorption will increase when intakes are low