Micronutrients

Question 1

What is the biochemical function of Iron

Answer 1

Tissue oxygenation
O2 transport in blood & muscle (Hb & myoglobin)
Electron transport (cytochromes)/respiratory chain
Enzymes for activation of O2 ( oxidases, oxygenases)
CNS myelination: Dopamine synthesis, (< 1% of total body iron)

Question 2

What are food sources of iron?

Answer 2

Heme:
Meats/flesh, liver
Non-heme:
Plant sources: legumes, whole grains, nuts;
Fe-fortified foods (infant formula, cereals/grains)

Question 3

Iron Absorption

Answer 3

Occurs in proximal duodenum
Ferroportin is the portal for iron into the body- regulation
Hepcidin blocks iron absorption- increased with inflammation
Phytate, excessive Zn or CU reduces iron absorption
Vit C helps with iron absorption

Question 4

Risk for iron deficiency

Answer 4

Poor bioavailability dietary Fe – plant/cereal staples
Dietary inadequacy – e.g. excessive milk intake
High demand
Hemolysis:  losses /  rbc production (e.g. helminths)
Pregnancy & infancy:  rbc production & growth, low stores at birth (“early” cord clamping)
Chronic immuno-stimulation ( hepcidin)

Question 5

Who’s at risk for iron deficiency?

Answer 5

BF Infants (> 6 mo ) - low stores / requirement
Premature/SGA infants
Young children - poor intake / ~  requirement
Adolescent girls/young women – menstrual loss
Pregnant women -   requirement
Blood loss (e.g. chronic infestations)
Obese (inflammation) & s/p bariatric surgery

Question 6

What are findings in iron deficiency

Answer 6

Microcytic, hypochromic anemia
decreased exercise tolerance
impaired cognitive function
fatigue

Question 7

How is iron deficiency diagnosed

Answer 7

Low Hgb

low serum FE with high TIBC

Question 8

What happens with iron toxicity

Answer 8

hemorrhagic gastroenteritis, shock, liver failure;± fatal

Hereditary hemochromatosis

Question 9

What is the biochemical function of Zn?

Answer 9

Regulation of gene expression (Zn fingers)
Stabilize molecular structures - subcellular constituents and membranes
Co-factor for hundreds of enzymes
Modulates activity of hormones & neurotransmitters
Sexual maturation
Growth & cellular/tissue proliferation
Immune Function

Question 10

Dietary sources of Zn?

Answer 10

animal sources
legumes, whole grains
Breast milk until 6 months

Question 11

What is the RDA of Zn?

Answer 11

Men 11mg
Women 8 mg
Pregnant- 13 mg

Question 12

Absorption of Zn

Answer 12

Determined by 2 factors:
The amount of zinc ingested
The dietary phytate

Question 13

Risk for Zn deficiency

Answer 13

BF Infants (> ~ 6 mo) & young children – high growth rate, low intakes
Pregnant & lactating women
Elderly – low intake
Monotonous. plant based diets:  phytate
GI illness/injury:   endogenous losses
Wounds/burns healing: tissue repair

Question 14

Symptoms of Zn deficiency?

Answer 14

dermatitis, personality changes, immune dysfunction, delayed sexual maturation, anorexia, diarrhea

Question 15

What is an inherited Zn deficiency

Answer 15

Acrodermatitis Enteropathica (AE)- stunting hypogonadism

Question 16

Why is linear growth velocity important?

Answer 16

growth velocity within the first year is predictive of IQ 9 years laters

Question 17

What happens with Zinc toxicity

Answer 17

High doses (> 50 mg/d) cause decreased Fe and Cu absorption 	(& neuropathy)
 High doses associated w/ decreased HDL-cholesterol 
nausea, diarrhea

Question 18

Zn deficiency while pregnant

Answer 18

congenital malformation, intrauterine growth retardation