Lecture 4-Selenium Flashcards
selenium is a what type of element and what does this mean
trace element = found in very small amounts in the body
what is the geographic intake of selenium intake like
large variations from deficiency to toxicity
what is the RDI of selenium for men and women
women is 60ug/day
men is 70ug/day
what is the New Zealand upper limit for selenium
400ug/day
there are different species of selenium, what are the ones that we need to remember
the organic ones
what are the organic species of selenium and their sources
selenocysteine (SeCys) = animal products
selenomethionine (SeMet) = plant products
in where is the selenium incorporated in a selenium protein
selenium is incorporated in the amino acid in place of sulfur
where does selenium enter the food chain and how does it get to us
enters the food chain through plants
- animals eat plants
- we eat animals and plants
what is the availability of Se in soil limited by
total soil Se content
bioavailability of Se to the plant
what makes Se less bioavailable to a plant
organic matter in soil absorbs Se ( makes it not available for the plant to take up )
Fe hydroxides, clay minerals bind Se (makes them unavailable)
how does pH of soil and selenium species affect the bioavailability
alkaline soils favour selenate > more bioavailable
acidic neutral soils favour selenide = less bioavailable
what are hyperaccumulators of selenium
accumulate > 1000mg Se/Kg DW in Se rich soils
food that demonstrates hyperaccumulators of selenium
brazil nuts = very efficient way to increase intake of selenium
what are secondary accumulators of selenium
exaple of these
accumulate up to 100-1000 mg Se/Kg DW
brassica (broccoli, cabbage)
allium (garlic, onions, leeks)
what are non accumulators of selenium
example in food
accumulate <100 mg Se/Kg DW
will only draw up small amount of selenium = how ever we eat a lot of them
wheat crops (wheat, oats, barley, rye)
rice
examples of Se low regions
NZ, Korea, Finland
examples of Se rich regions
USA, Canada, Japan, China
common food sources of selenium
brazil nuts
mussels
lamb kidney
blue cod
mushroom
what is the intake of Se like in New Zealand
low soil in NZ = low intakes however this changes throughout the country
in the 2008 nutrition survey what was the main source of selenium in NZ
bread = not super high in selenium but we consume a lot of it
what part of NZ has higher Se levels and why
North island has higher levels than south island
Bread in north island is imported from high Se areas in Australia and US
why is the Se content of animal products more reliable than plants
animals have an absolute requirement for Se, so the content will reflect what you eat but plants depend on bioavailability