selenium

Question 1

what type of element is selenium

Answer 1

a trace element

Question 2

selenium is Present in foods bound to what protein amino acids

Answer 2

acids methionine and cystine, as selenomethionine (plants) and selenocysteine (animals)

Also selenide (H2Se), selenite (H2SeO3) and selinate (H2SeO4) found in beets, cabbage, yeast

Question 3

selenium is absorbed through what

Answer 3

Absorbed through amino acid transporter

Question 4

explain the varying absorption of different selenium forms in food

Answer 4

(SeMet > SeCys,
eg Plant material sources are better sources as more bioavailable and better absorbed)

Question 5

explain why we need selenium

Answer 5

To make seleno proteins

Glutathione Peroxidase (a selino protein) :

Antioxidant enzyme – part of cellular defence system, protecting aginst free radicals and oxidative stress. It converts H2O2to water
Peroxides converted to hydroxy forms e.g. LOOH converted to LOH

In the process, 2GSH oxidised to GSSH (eg glutathione is converted into oxidised form to detoxify lipid peroxide to protect against oxidative stress)

Question 6

what do deiodinases do

Answer 6

Remove iodine molecules from thyroxine e.g conversion of T4 to T3
T3 is biologically active. All thyroid hormones are mediated by T3

Question 7

what are selenoproteins involved in

Answer 7

many are involved with antioxidant reactions
Selenium is important in thyroid function and protect against oxidative stress

Question 8

what are the requirements of selenium based on and how do we measure this

Answer 8

based on glutathione peroxidase activity

we measure this by looking at saturation of enzyme, above intakes of 41 µg/day (LRNI set at 40 µg/day)

Question 9

what are the RNI requirements for men and women and explain the difference

Answer 9

RNI in males is 75 µg/day
RNI in females is 60 µg/day

Males need more than females as are more muscular. Physical activity is associated with oxidative stress, so as more muscular they generate more free radicals from physical activity so require greater amounts of selenium

Question 10

explain selenium deficiency

Answer 10

No clear clinical deficiency state
Selenium in soil in china is particularly low so they are at risk of deficiency as are very very low intake of selenium

Keshan disease (very dangerous as means there muscle isn’t strong enough and isn’t contracting strongly enough):
In China, intakes below 12 µg/day increased incidence of Selenium-responsive cardiomyopathy

Kashin-Beck’s disease:

what see is osteoarthropathy – so develop osteo arthritis which is sensitive to selenium

The 2 deficiency occur in different areas of china. The deficiency makes then vulnerable to something in their environment as don’t have same antioxidant defence in their cells. Rather than it causes these deficiencies, it just makes them more vulnerable to these environmental stresses. The antioxidant defences protect us from these oxidative stresses from the environment.

Question 11

when does selenium deficiency occur

Answer 11

occurs in long term parenteral nutrition (when put nutrients straight into a vein)

Question 12

explain symptoms of selenium deficiency

Answer 12

Poor growth (which associated with low thyroid function)
Muscle pain
Depigmentation of skin, hair

Question 13

Serum [selenium ] inversely linked to risk of what

Answer 13

Serum [selenium ] inversely linked to risk of heart disease and some cancers e.g oesophageal; stomach.
Eg higher ur selenium level the lower ur risk in developing these diseases

Question 14

what are some good sources of selenium

Answer 14

nuts and seeds