micronutrients and minerals

Question 1

define a trace mineral

Answer 1

Mineral for which daily intake is < 100 mg.

Question 2

Define bioavailability and how this relates to minerals

Answer 2

Bioavailability: the extent to which other dietary constituents affect the absorption & retention of a nutrient. Trace minerals especially susceptible to interference w/ absorption

Question 3

functions of iron

Answer 3

1. O2 transport in blood & muscle (Hb & myoglobin). 2. Electron transport (cytochromes). 3. Enzymes for activation of O2 (wbc, oxidases, oxygenases). 4. Enzymes: dopamine synthesis, CNS myelination (< 1% of total body iron)

Question 4

Total body iron

Answer 4

5g. 50% as hemoglobin

Question 5

Iron sources

Answer 5

Heme: meats/flesh, liver. Milk is poor source. Non heme: legumes, whole grains, nuts, Fe fortified foods (infant formula, cereals, grains)

Question 6

compare absorption of heme vs non heme iron

Answer 6

absorption of non-heme iron, much lower (<10%) compared to animal sources (≥ 20%)

Question 7

Factors affecting absorption of Fe

Answer 7

Insoluble complexes in plants inhibit absorption: phytate binds Zn, Fe and Ca in gut (maize/wheat > legumes > rice), oxalate, polyphenols (tea), phosphate, fiber.

Question 8

iron homeostasis

Answer 8

Absorbed better in Fe2+ form (ascorbic acid reduces Fe). Also host factors- if deficiency, increased absorption. If inflammation, decreased absorption b/c hepcidin produced by liver decreases uptake by enterocytes.

Question 9

main site of Fe regulation

Answer 9

intestinal absorption- once absorbed, it is efficiently retained

Question 10

Stores of Fe

Answer 10

ferritin- liver, bone marrow, spleen

Question 11

function of transferrin

Answer 11

transports Fe in body

Question 12

Who is at risk for iron

Answer 12

Breast fed infants (>6months) due to low stores and high requirement. Premature infants. Young children due to poor intake and increased requirement. Women due to menstrual loss. Pregnant women due to increased requirement. Blood loss. Obese pts (inflammation) and bariatic surgery

Question 13

how do iron needs change over time in infancy

Answer 13

At 12 months, needs double b/c increased hemoglobin production

Question 14

Causes of iron deficiency

Answer 14

1. poor bioavailability of dietary Fe- plant/cereal staples. 2. dietary inadequacy- excessive milk intake 3. high demand: hemolysis, pregnancy, infants. 4. Chronic immuno-stimulation: increased hepcidin

Question 15

Effects of iron deficiency

Answer 15

1. decreased work capacity/exercise tolerance. 2. fatigue, irritability, sleep disturbance. 3. impaired growth. 4. anemia (microcytic, hypochromic). 5. ID without anemia - impaired cognitive function in developing brain (irreversible)

Question 16

Iron toxicity

Answer 16

Potent pro-oxidant. Can lead to decreased growth, oxidant stress, decreased neuro-cognitive development, increased inflammatory markers, and effect on microbiome. Also hemorrhagic gastroenteritis, shock, liver failure, death

Question 17

Hereditary hemochromatosis

Answer 17

defect in hepcidin leads to excessive absorption > accumulating Fe > liver damage

Question 18

Iron deficiency without anemia

Answer 18

–Behavioral & learning/developmental effects

Question 19

iron deficiency in setting of acute inflammation

Answer 19

Absorption will be poor due to hepcidin stimulation. Administering Fe can be pro-inflammatory and ineffective. Likely cause of iron deficiency in devloping coutnries

Question 20

Zinc function

Answer 20

1. Regulation of gene expression (Zn fingers). 2. Stabilize molecular structures - subcellular constituents and membranes. 3. Co-factor for hundreds of enzymes. 4. Modulates activity of hormones & neurotransmitters

Question 21

total body zinc

Answer 21

2g

Question 22

Physiologic roles of zinc

Answer 22

1. growth and tissue proliferation- somatic/linear growth, immune system, wound healing, GI tract integrity, skin. 2. antioxidant. 3. sexual maturation. 4. sense of taste

Question 23

Zinc sources

Answer 23

Beef > poultry > fish (animal sources greatest), plants (whole grains, legumes)

Question 24

Zinc absorption

Answer 24

inhibited by phytate, typically 25-30% absorbed, NOT increased by Zn deficiency. Lower absorption from plant foods.

Question 25

Zinc homeostasis

Answer 25

Minimal control of absorption. Secretion and reabsorption/excretion are controlled

Question 26

compare zinc vs Fe homestasis

Answer 26

Fe is not excreted, Zn is!

Question 27

Zinc in milk

Answer 27

Levels are high at birth, then decrease over the course of 10 months

Question 28

Who is at risk for zinc deficiency

Answer 28

Breast fed infants and young children, pregnant and lactating women, elderly (low intake), monotonous plant based diets (increased phytate), GI illness/ijury (increased losses), wound/burns (tissue repair)

Question 29

Clinical sx of moderate to severe zinc deficiency

Answer 29

dermatitis, personality changes, immune dysfunction, delayed sex maturation, anorexia, diarrhea, stunting and hypogonadism

Question 30

Inherited defect in Zn absorption

Answer 30

Acrodermatitis Enteropathica (AE)- presents as severe zinc deficiency

Question 31

mild zinc deficiency clinical sx

Answer 31

growth delays, anorexia, impaired immune function

Question 32

Is mild or moderate/severe Zn deficiency more common?

Answer 32

mild

Question 33

Stunting is associated with what mineral

Answer 33

zinc deficiency

Question 34

impact of Zn supplementation in young children in developing countries

Answer 34

decreased incidence of diarrhea, pneumonia and deaths

Question 35

zinc toxicity

Answer 35

Occurs less than iron. Causes decreased Fe and Cu absorption (and neuropathy). Also decreased HDL and impaired immune function

Question 36

benefits of high zinc

Answer 36

May prevent macular degeneration and help with acute pharyngitis