Trace Minerals Flashcards
Iron
two forms: ferrous (reduced/2+) and ferric (oxidized/3+)
RDA = 18 mg/d (F)
27 mg/d (pregnancy)
8 mg/d (M)
Iron functions
heme protein/O2 carrier electron transport cytochromes activators of molecular oxygen - monooxygenase (H) - cytochrome P450 (H) - peroxidases (H) - catalases (H) - hydroxylases (NH) - lipoxygenases (NH) DNA synthesis: ribonucleotide reductase (NH)
Heme iron
better absorbed than non-heme
10% of daily Fe intake
Non-heme iron
plant-derived and in meat
(60% of iron from meat = non-heme))
poorer absorption than heme iron
enhanced absorption with MFP factor, Vit C, citric/lactic acid, fructose
absorption inhibited by phytates, vegetable proteins, calcium, and tannic acid
Iron metabolism
stored as ferritin
- short-term = intestinal mucosal cells
- long-term = liver
transported as transferrin (carries 2 atoms, must be oxidized, which requires copper)
Iron-nutrient interactions
zinc - Fe may inhibit its absorption d/t shared transport protein
calcium - decr Fe absorption
copper - required to oxidize Fe; Cu deficiency may exacerbate IDA
Iron toxicity
iron overload hemochromatosis - cirrhosis - DM - cardiomyopathy
Iron deficiency
storage depletion early functional iron deficiency IDA (microcytic/hypochromic): - ssx = fatigue, weakness, tachycardia, tachypnea restless leg syndrome impaired cognitive development in children: - hypomyelination - disrupted dopamine metabolism
Risks for iron deficiency
children 6 mo - 4 yo pregnancy blood loss celiac dz vegetarians/vegans regular intense exercise
Iron sources
heme - meat, poultry, fish
non-heme - meat, nuts, seeds, legumes, green leafs
cast iron cookware
Copper
2+ = cupric/oxidized \+ = cuprous/reduced
important for redox rxns
incorporated into cuproenzymes
RDA = 900 mcg/day UL = 10,000 mcg/day (10 mg)
Copper functions
iron metabolism: absorption/heme synthesis/ferroxidases
energy production: ETC/cytochrome c oxidase
nervous sys function: DA production/myelin synthesis
collagen synthesis/cross-linking
melanin synthesis: tyrosinase fx
anti-oxidant: SOD
Copper:
nutrient interactions
iron - part of Fe transport protein
zinc - competitive inhibition (must add Cu to Zn supplementation)
vitamin c - supplementation may induce deficiency
Copper excess
Wilson’s dz (AR)
= accumulation of copper in brain and liver
Copper deficiency
unresponsive IDA
Copper food sources
seafood (esp oysters) nuts seeds legumes whole grains liver
Zinc
RDA =
8 mg/day (F)
11 mg/day (M)
UL = 40 mg/day
95% = intracellular, mostly in muscle and bones
Zinc absorption
inhibited by : phytates, divalent cations (calcium/iron)
enhanced by : protein
absorption rate varies from 5 - 50%
Zinc functions
catalytic (>300 metalloenzymes)
structural
regulatory - cell signaling/gene regulation
Zinc : enzymatic functions
insulin production taste perception vit A metabolism (retinol >>> retinal) wound healing spermatogenesis growth of developing fetus digestive enzymes (esp brush border)
Zinc : structural importance
zinc fingers = protein stabilization of AA sequences high in cys and his
- SOD (requires Zn and Cu)
metallothionein (intracellular transport protein)
- regulates Zn uptake/transport/regulation
- modulates oxidative stress
- regulates gene transcription
Zinc : regulatory
Gene repression/activation
- apoptosis
- cytokine gene regulation
Cell signaling pathway regulation
- hormone release
- nerve impulse transmission/gate kinetics
(affects NDMA and GABA)
Zinc toxicity
N/V/D
HA
fatigue
impaired copper absorption/deficiency
usu d/t supplementation
Zinc deficiency : children
stunted growth/immature sexual development
Zinc deficiency : adults
- impaired digestion/absorption
- poor motor/cognitive ability
- impaired vitamin A metabolism (photophobia/night blindness)
- weakened immune system : decr phago/depressed T cell fx/impaired cytokine production
- alopecia
- skin lesions/nail dystrophy
- delayed wound healing
Zinc food sources
meat eggs seafood - posters, lobster, crab legumes nuts dairy
Iodine
necessary for thyroid function
RDA = 150 mcg/day
pregnancy - 220 mcg/day
lactation - 290 mcg/day
UL = 1100 mcg/day
Iodine : thyroid
thyroid uptake regulated by TPO
TPO = heme-containing protein
IDA may»_space;> decr thyroid function
affected by anti-TPO Aby of hashimoto’s
Iodine excess
goiter
Iodine deficiency
goiter
decr thyroid hormone production
cretinism
selenium def may exacerbate iodine def
Iodine food sources
seafood seaweed iodized salt (0.5 tsp = RDA) dairy plants grown in iodine-rich soil (coastal)
Goitrogens
spinach cabbage/broccoli/kale soybeans peanuts peaches strawberries >>> bind iodine, making it unavailable for absorption cooking limits this
Selenium
incorporated into proteins (selenoproteins)
- antioxidant systems : GSH peroxidase
- thyroid metabolism : iodothyronine deiodinase
RDA = 55 mcg/day
UL = 400 mcg/day
Selenium excess
loss/brittleness of hair and nails
rare
Selenium deficiency
may exacerbate iodine def
immune dysfx
Keshan disease - cardiac abN»_space;> fibrous cardiac muscle
Selenium food sources
brazil nuts meat seafood eggs whole grains brown rice mushrooms produce - soil dependent
Manganese
important for function of metalloproteins
- SOD
- xanthine oxidase
- arginase
- glutamine synthase
- prolidase (collagen synthesis)
Manganese absorption
9-16% absorbed in SI
most concentrated in mitochondria
25% stored in bone
AI = 2.3 mg/d for M; 1.8 mg/d for F UL = 11 mg/d
Manganese deficiency
maybe CT/bone issues
correlation with seizures and DM II
Manganese excess
not from diet, maybe from environment (pesticides)
|»_space;> CNS disturbances and Parkinson-like sxs
Manganese food sources
whole grains - oats legumes nuts coffee tea spinach pineapple
Chromium
component of holochromodulin
- incr insulin receptor activity
0.5 - 2.5% absorbed from diet
AI = 25 mcg/d (F); 35 mcg/d (M)
UL not established
Chromium deficiency
impaired glucose metabolism
Chromium excess
teratogenic, genotoxic, carcinogenic
|»_space;> kidney failure (1 mg/d for > 6 weeks)
Chromium food sources
broccoli whole grains legumes nuts meat
Molybdenum
important for O2 transport
component of :
- molyboenzymes of N metabolism (nitrate»_space; ammonium)
- xanthine oxidase
- sulfate oxidase (cys and met metabolism)
AI = 45 mcg/d
UL = 2 mg/ d
Molybdenum deficiency
very rare inborn metabolic disorders»_space;>
- cerebral atrophy
- intractable seizures
Molybdenum excess
little evidence of toxicity
potential for seizures, hallucinations, gout-like sxs
Molybdenum food sources
legumes - lentils/peas
whole grains
nuts
avg intake = 76 mcg/d (F); 110 mcg/d (M)
Fluoride
95% in bones/teeth
prevents dental caries
not considered essential mineral
AI = 4 mg/day UL = 10 mg/day
Fluoride sources
black tea
fruit juice
crab
municipal water
