Iron, Zinc and Iodine Flashcards
1
Q
What are the amounts of micronutrients needed?
A
ug or mg
2
Q
Are micronutrients essential? Why?
A
- Not synthesized at rates sufficient to meet requirements
- Perform specific biological functions
- If withdrawn, deficiency occurs
3
Q
Compare reversible and irreversible vitamin A deficiency.
A
Reversible: night blindness
Irreversible: blindness
4
Q
Name the pigment that is non-essential.
A
Beta-Carotene, nothing happens if withdrawn
5
Q
Define bioavailability.
A
% mineral ingested that is available for absorption
6
Q
How is bioavailability highly variable?
A
Absorption can vary with need (ex: iron - 5%-50%)
7
Q
Name 3 characteristics of bioavailability.
A
1) Potential toxicity from excess
2) Metabolic interactions (transporting)
3) General function in metalloenzymes or at least metalloproteins
8
Q
Give an example of how micronutrients can function in metalloenzymes.
A
In redox reactions
9
Q
Name the most abundant minerals.
A
Calcium -> phosphorus -> potassium -> sulphur -> sodium -> chloride -> magnesium
10
Q
Name the minerals that are electrolytes.
A
Potassium, sodium, chloride
11
Q
Which minerals appear in amounts higher than 1/2 a kilogram?
A
Calcium and phosphorus
12
Q
What is free calcium used for?
A
Nerve impulse transmission
13
Q
Where is calcium kept?
A
99% in bones
14
Q
Where is iron mostly circulating?
A
Red blood cells
15
Q
Define vitamins.
A
Essential organic nutrients required in small amounts
16
Q
Which vitamin was first discovered?
A
Vitamin B1: Beriberi
17
Q
Define vitamers.
A
Different forms of a vitamin that can have different functions, conversion between forms and from precursors
18
Q
What is the general function of vitamins?
A
As coenzymes
19
Q
Name the fat soluble vitamins.
A
A, D, E, K
20
Q
Name the water soluble vitamins.
A
B complex, C
21
Q
Vitamins are subject to what in food?
A
Degradation (light, oxygen, temp)
22
Q
Why is there no vitamin F?
A
Whatever was proposed as vitamin F turned out not to be essential
23
Q
Why are there so many vitamin Bs?
A
They thought it was just one compound, pulled out, found 12 different ones
24
Q
What are the B vitamins essential for?
A
Intermediary metabolism
25
What is vitamin B1?
Thiamin
26
What is vitamin B2?
Riboflavin
27
What is vitamin B3?
Niacin
28
What is vitamin B5?
Pantothenic acid
29
What is vitamin B6?
Pyridoxine
30
Which B vitamins is the RDA based on energy?
B1 to B5
31
Which B vitamins is the RDA based on protein?
B6
32
How would an enzyme function without its coenzyme?
Wont catalyse, inactive, no chem reaction
33
Name 2 hormonal functions of vitamins.
- Vitamin A as retinoic acid - cell differentiation
| - Vitamin D as calcitriol - Ca availability
34
Name an antioxidant function of vitamins.
Vitamin C and E -> lipid soluble, protect lipid membranes from fatty acids being oxidized
35
Define hypochromic.
Low in colour red cells
36
Define microcystic.
Small, low hemoglobin
37
How are the red blood cells in iron deficiency?
Hypochromic and microcystic
38
How are the red blood cells in folate or vitamin B12 deficiency?
Megaloblastic or pernicious anemia
39
Name examples of structures made from amino acids but are NOT a protein.******
- Heme
40
Define the structure of hemoglobin.
- 4 protein units, each has a disk, each has an iron
41
What is the function of myoglobin?
Muscle storage of oxygen
42
What is the main function of iron?
Carries oxygen
43
How do we diagnose iron deficiency anemia?
1st stage: serum ferritin
2nd stage: serum iron falls and transferrin increases
3rd stage: hemoglobin decreases
44
Name the signs and symptoms of iron deficiency anemia.
- Weakness, fatigue, headaches
- Decreased work performance and cognitive function
- Pale skin, nail beds, mucous membranes, and palm creases
- Concave nails, inability to regulate body temperature, pica
- Decrease in childhood development (psychomotor and intellectual)
45
Why does iron deficiency anemia increase lead poisoning susceptibility?
Fe2+ ressembles Pb2+
There is a transporter for the +2 cation, if someone is iron deficient the adaptation is to increase the efficiency of the absorption from the intestine, there is an increase in those active transporters, less competition from iron, more efficient iron of lead
46
What hemoglobin concentration indicates iron deficiency anemia in men? Women?
Men: Hgb < 140 g/L
Women: Hgb < 120 g/L
47
Compare the prevalence of iron deficiency in developed vs. developing countries.
Developing: 50% women + children, 25% men
Developed: 7-12% women + children
48
What percentage of low income infants in Montreal have iron deficiency?
25%
49
How many people worldwide have iron deficiency anemia?
4-5 billion people
50
What should iron metabolism be if an individual is healthy?
Iron intake = Iron losses
51
Describe free iron.
Toxic (oxidative stress)
52
Describe iron metabolism.
Learn it
53
How do you make Heme?
Fe2+ and protoporphyrin
54
How many transfer sites does transferrin have?
6
55
How long do circulating RBCs live?
120 days
56
What makes feces brown and urine yellow?
Bilirubin
57
In what state does iron function in?
2+ state
58
Compare Fe2+ and heme sources in terms of absorption.
Fe2+ : not well absorbed (10%)
| Heme: up to 50% absorbed
59
Why does vitamin C help iron absorption?
It is a reducing agent: Fe3+ to Fe2+ = more absorbed
60
What substances will decrease iron absorption?
Coffee and tea
61
Define the 4 components of iron balance.
1) Iron intake (dietary iron + bioavailability)
2) Amount of iron in storage
3) Rate of erythrocyte production
4) Iron losses
62
How do we measure advanced iron deficiency?
Measure hemoglobin (abnormal functions in the body)
63
How do we measure primary deficiency of iron?
Primary: food diary
64
How can we know more about iron liver stores?
Some of ferritin is circulating in plasma, measuring ferritin can tell us about liver stores
65
Define free erythrocyte protoporphryin.
Defective process of making red blood cells: some red blood cells are JUST protoporphryin (no Fe2+)
66
Name the 4 sequential changes with development of iron deficiency.
1) Depletion of iron stores
2) Changes in iron transport
3) Defective erythropoiesis
4) Iron deficiency anemia
67
What happens during depletion of iron stores?
decrease in plasma ferritin
68
Name the 4 changes during changes in iron transport.
1) Increased absorption efficiency
2) Increased transferrin iron binding capacity
3) Decreased transferrin saturation %
4) Increased transferrin receptors
69
What happens during defective erythropoiesis?
1) Decrease plasma iron
| 2) Erythrocyte protoporphyrin
70
What happens during iron deficiency anemia?
1) Microcystic hypochromic erythrocytes
| 2) Associated behavioural signs
71
Name the 4 causes of iron deficiency.
1) Decreased dietary iron
2) Inhibition of absorption
3) Increased red cell mass
4) Increased losses
72
Why would decreased dietary iron cause iron deficiency?
- Less iron absorbed
| - Vegetarians lack heme
73
Why would inhibition of absorption cause iron deficiency?
- Mineral interaction: Ca, Zn supplements decrease Fe absorption
- Absorption inhibitors
74
Why would increased red cell mass cause iron deficiency?
Pregnancy, growth
75
Why would increased losses cause iron deficiency?
Hemolysis, GI bleeding (occult), heavy menstrual losses
76
How many grams of iron do we have in RBCs? Is there a lot of iron in stores?
- 2.4 g in RBCs
| - Very little in stores
77
What are treatment options for iron deficiency anemia?
- Changes in diet
- Supplements (3.5 mg elemental iron + 100 mg sulphate = ferrous sulphate)
- Retest after 1-3 months
78
What are prevention options for iron deficiency anemia?
Fortify food supplies (FeSO4 added to flours)
79
What is the problem with iron supplements? And multivitamins?
- Multivitamins only have 8 mg of iron
| - Supplements cause serious constipation
80
Describe the characteristics of heme iron.
- 10% dietary iron
- Hemoglobin and myoglobin (meat, fish, poultry)
- 25% absorbed, absorbed as Heme
81
Describe the characteristics of elemental iron.
- 90% of dietary iron
- Mostly plants (nuts, fruits, veggies, enriched grains)
- 1-50% absorbed, mostly under 10%
82
What is elemental iron absorption increased by?
Sugars, vitamin C, acids (including amino acids)
83
What is elemental iron absorption decreased by?
Calcium, Phosphorus, phytates, oxalates, polyphenols, tannis, EPTA
84
Name some good sources of iron.
Clams (canned), beef liver, parsley, legumes and meat
85
Why is the variability of absorption of elemental iron high?
Depends on what you eat it with
| ex: taking an iron supplement with orange juice is good (vit C)
86
What is a good iron supplement for infants?
Ground meat (Heme)
87
Name 3 adaptations to increase iron availability in deficiency.
1) Increase efficiency of absorption and release from intestinal epithelial cells
2) Increase transferrin synthesis and transferrin receptors
3) Decrease ferritin synthesis
88
Explain how iron is transferred. What does it require?
- Taking iron out of membrane: Fe3+ to Fe2+
| - Requires copper, vitamin B2 and B3 (riboflavin, niacin)
89
Iron deficiency can be secondary to what?
To copper deficiency (not common, fortified in water)
90
How many transferrin sites are usually saturated? What is it occupied by?
1/3, occupied by Fe3+
91
What does low saturation of transferrin indicate?
Indicates deficiency of iron
92
What does high saturation of transferrin indicate?
Indicates over-supply of iron
93
How can transferring receptors be regulated?
Highly regulated, increase in iron adequate environment and decrease in iron rich environment
94
Where is iron stored?
Liver, bone marrow and spleen
95
What kind of iron is stored?
Ferritin or homosiderin
96
How many grams is total body iron?
2.5 to 3.8 grams
97
What is a window on iron stores?
Plasma ferritin
| - 1 microgram/L plasma = 10 mg storage iron
98
Compare the total daily iron losses for men and women.
Men: 1.0 mg
Women: 1.4 mg
99
Name the 4 types of iron losses.
1) GI losses (GI blood, GI mucosal, bile)
2) Desquamated skin cells and sweat
3) Urinary losses
4) Menstrual losses
100
When do women lose iron from their periods?
Not just during 5 days, relatively constant during month, reason why women need more iron ALL the time
101
What percent of absorption of iron does the RDA take into account?
10-15%
102
What is the RDA for iron for men? Women?
Men: 8 mg (only 1mg loss, RDA takes into account)
Women: 18 mg
103
What percentage of women meet the RDA for iron?
25%
104
What is the RDA for women on contraceptives, pregnant, and vegan?
Contraceptives: 11mg/d (less)
Pregnant: 27 mg/d (more)
Vegan: 33mg/d (more)
105
What is the UL for iron?
45 mg/d
106
What is the DRI value for iron in mg? Why?
- 14 mg/d
| - In between men and women
107
Name 3 reasons that can cause iron overload and toxicity.
1) Acute iron toxicity or poisoning (supplements)
2) Iron overload from repeated transfusions
3) Megadoses of vitamin C (pro-oxidant)
108
How can megadoses of vitamin C cause iron overload?
- Can reduce ferric iron bound to transferrin to free ferrous iron
- Free iron is a powerful oxidant: fenton reaction (formation of free radicals from reactive oxygen species)
109
Define hemochromatosis.
- Chronic overload with potential tissue damage
- Very efficient iron absorption due to defective hepcidin production (hormone that inhibits iron release from intestinal epithelial cells)
110
What is the cause of hemochromatosis? Treatment?
Cause: iron deposition as hemosiderin, cirrhosis
Treatment: phlebotomy
111
Name some functions of zinc.
- Zinc is involved in everything, makes deficiency difficult to diagnose
- Metalloenzyme: DNA and protein synthesis, growth/development
112
Name some sources of zinc. What is it not in?
- Beef, seafood, legumes, oysters, crab
| - Not in fruits/veg
113
What is zinc deficiency misdiagnosed as?
General protein energy malnutrition
114
Why can't we measure zinc in the plasma?
Since it switches forms, there is no specific zinc test
115
What substance in the body is high in zinc?
Pancreatic juice
116
Which population group is most vulnerable to zinc deficiency?
Children: poor appetite, compromised growth
117
What is parakeratosis?
Rash specific to zinc deficiency
118
How were pigs used to define parakeratosis?
To find specific biomarkers for mild zinc deficiency
119
Explain the enteropancreatic circulation of zinc.
Learn it.
120
What does the pancreas use zinc for?
To make digestive enzymes and secretes them into the digestive tract
121
During deficiencies, is absorption higher in zinc or iron?
Zinc > iron
122
Name the enhancers of zinc absorption.
Acids and amino acids
123
Name the inhibitors of zinc absorption.
Phytates, oxalates, polyphenols, fibre (insoluble) other cations, folate, H2 blockers
124
How is zinc homeostatically regulated?
- Absorption efficiency of dietary zinc (increased with low intakes)
- Endogenous secretions in pancreatic fluid (endogenous fecal losses increase several folds at high intakes)
125
Name the 4 steps in dietary zinc deficiency.
1) Increased absorption/decreased losses (re-establishes homeostasis)
2) Tissue zinc conversion
3) Mobilization of zinc from exchangeable pool
4) General tissue dysfunction
126
What is copper deficiency induced by? How? How does it impact iron?
- By zinc toxicity
- Increased intestinal metallothionein, copper not released in blood, lost in shed mucosal cells WHICH could impact iron (small pale RBCs)
127
What are symptoms of acute zinc toxicity?
nausea, vomiting, diarrhea
128
What is copper deficiency characterized by?
Decreased ceruloplasmin
129
Name the 2 kinds of signs and symptoms for copper deficiency.
- Iron deficiency S&S since you can't get iron out of intestinal epithelial cells
- Liver: iron overload S&S because you can't get iron out of stores
- -> decreased ceruloplasmin (contains ++ copper) which reduces iron transport
130
Name the 2 thyroid hormones.
Thyroxin (T4) and T3
131
Name a non-protein product of amino acids.
Tyrosine with 3 or 4 iodines = thyroid hormones (T4 or T3)
132
What are the roles of the thyroid hormones?
Metabolic rate of every cell, body temperature, RBC synthesis, growth, reproduction, brain development
133
What are the consequences of iodine deficiency (Severe)?
Goiter, super enlarged thyroid because thyroid hormone production declines
134
Is iodine deficiency the only cause of goiter?
The only nutritional based cause
135
How many people does goiter affect?
200 million
136
What is cretinism? Who does it affect?
Babies, brain development, iodine deficiency
137
What is the treatment for iodine deficiency?
exogenous thyroid hormones
138
Why is iodine deficiency not a problem in North America?
Fortified table salt
- Delivers RDA in 2 g of salt
- Avg consumption of salt is 8g/d in USA
139
Explain how iodine deficiency develops.
1) Decrease in T3 and T4 due to decreased iodine
2) Hypothalamus acts on
3) Pituitary gland, which acts on thyroid stimulating hormone (TSH)
4) If the deficiency persists, cells of the thyroid gland enlarge to trap as much iodide as possible -> visible lump
* If no iodine, no negative feedback, continuously stimulated thyroid gland -> enlarged thyroid -> goiter
140
How does high levels of iron affect zinc?
Iron overload (Fe occupies all transferrin binding sites) decreases zinc absorption and transport
141
How does high levels of zinc affect copper?
High diet in zinc increases metallothionein (copper bound more strongly), not released from mucosal cells, copper deficiency
142
How does low levels of protein affect zinc?
Less albumin, less zinc released from mucosal cell: more growth failure, immune dysfunction
143
What is the role of ceruloplasmin in iron transport?
Oxidizes iron from its ferrous state to the ferric form that is required for iron binding
144
What is niacin a precursor for?
NAD+, NADP
145
What is riboflavin a precursor for?
FAD, FMN
146
What is pantothenic acid a precursor for?
CoA in acetyl CoA
147
What is thiamin necessary for? Pyridoxine?
```
Thiamin = pyruvate decarboxylation
Pyridoxine = transamination reactions
```
148
What is the RDA for zinc for men? Women? UL?
- Men: 11mg/day
- Women: 8mg/day
- UL = 40 mg/day
149
What is the absorption efficiency of zinc?
33%
150
How is iron balance primarily maintained? Is it difficult to excrete iron?
- Primarily through absorption
| - It is difficult to excrete iron
