2.3 Macro and microminerals reqs in adults Flashcards
Calcium
- 3 functions
- AI/RDA based on what?
- 98-99% of bones and teeth –> hydroxyapatite
- second messenger in intracellular signaling
- nerve cell signaling
RDA based on Ca2+ balance studies –> intakes to achieve small gains in bone mass concentration –> based on clinical trials showing an increase in bone mineral density in women provided with intakes of 1000 mg/d
reqs for calcium? UL?
EAR = 840 mg/day
RDA = 1000 mg/day
for both men and women 19-50 yo
UL = 2500 mg –> based on supplements
- excessive calcium will block iron
- heart disease in post-menopausal women
- increase risk of prostate cancer for men
- downregulation of vit D2
- large amount at once (from supplement) –> increase risk of plaques (atherosclerosis)
Phosphorus:
- occurs as what? –> in 3 types of molecules ish
- essential constituent of what?
- how can it maintain normal pH?
- temporary storage for what?
- required for _________ for the activation of what?
- occurs at PO4 –> in phospholipids, nucleotides, nucleic acids
- essential constituent of bones –> 85% of adult body P is in bone
- buffers acid and alkali XS to maintain normal pH (in bones)
- temporary storage and transfer of energy derived from metabolic fuels
- required for phosphorylation –> activation of many catalytic proteins
Phosphorus:
- EAR based on what?
- intake = amount absorbed?
- EAR/RDA?
- UL?
- based on lower end of the normal [Pi] range (0.86 mmol/L)
- need 18.7 mmol/L (580 mg) of intake to = 0.86 mmol/L
- EAR = 580 mg/day
- RDA = 700 mg/day
for both women and men >=19yo - UL = 4000 mg
- causes hyperphosphatidemia –> disrupts normal calcium metabolism
Magnesium:
- 50-60% in ______ –> 1/3 exchangeable for what?
- required _________ for what?
- 50-60% in bone! –> 1/3 skeletal Mg exchangeable as reservoir for maintaining normal extracellular [Mg]
- required cofactor for over 300 enzyme systems
Magnesium:
- EAR based on what?
- EAR/RDA?
- UL?
- based on maintenance of total body Mg (balance studies)
RDA: - Men 19-30 yo: 400mg/d
- Men > 30 yo: 420 mg/d
- Women 19-30 yo: 310 mg/d
- Women >30 yo: 320 mg/day
*over 30, decrease in tubular kidney function so need to increase - UL = 350 mg based on supplements NOT dietary sources of magnesium (ie nuts and seeds)
- adverse effect = osmotic effect, diarrhea, bloating, GI effects
IRON:
- component of which proteins (3 ish)
- almost 2/3 in Hb (erythrocytes)
- 15% in myoglobin in muscle
- rest in variety of iron containing enzymes necessary for oxidative metabolism and many other critical functions
what are the factors that are included when evaluating iron requirement? (4)
- EAR based on which losses for men vs women?
- basal iron losses (hair, skin, urine, feces)
- menstrual losses
- fetal requirements in pregnancy
- growth: expansion of blood volume and/or increase tissue and storage iron
- men: basal iron losses
- women: basal iron losses + menstrual losses
what is the iron EAR based on? (2 ish)
- based on need to maintain a normal, functional [Fe]
- but only a minimum store (serum [ferritin] of 15 ug/L)
major difference btw heme and non-heme iron?
- present in what foods?
major factor = bioavailability!
HEME IRON:
- meat, poultry, fish
- always well absorbed, slightly influenced by dietary factors (vit C)
NON-HEME IRON:
- present in all foods in ferric (3+) form
- strongly influenced by solubility and interaction with other meal components
- food iron is released by what in stomach?
- must be in what form for uptake by duodenal enterocytes?
- what food factors can reduce ferric to ferrous?
- which type of iron in more readily absorbed?
- which 3 things will decrease absorption of iron?
- released by acid digestion in stomach
- must be reduced to ferrous (Fe2+) prior to uptake by duodenal enterocytes
- ascorbic acid can reduce ferric (3+) to ferrous (2+) in intestinal lumen
- ferrous! and is present only in animal sources
- elevated levels of oxalic acid in vegetables, phytic acids in grains and tannins in tea will decrease iron absorption
- EAR/RDA based on what % bioavailability of iron?
- EAR set by estimating requirement for absorbed iron at which percentile? vs RDA?
- 18% bioavailability/absorption –> from typical mixed diet
- estimating reqs for absorbed iron at 50th percentile for EAR
- vs 97.5th percentile for RDA
which 2 populations are more at risk of iron deficiency? how to adjust requirement?
- completely vegetarian diet
- 14 mg/d for adult men and post-menopausal women (instead of 8 mg)
- 33 mg/d for premenopausal women (instead of 18 mg) - athletes doing intense exercise
- increase microscopic bleeding from GI tract, increased fragility of RBC
- avg requirement for iron may be 30% higher
EAR and RDA of iron for men vs women?
- UL?
MEN:
- EAR = 6 mg/d
- RDA = 8 mg/d
WOMEN:
- EAR = 8.1 mg/d
- RDA = 18 mg/d
UL = 45 mg from supplements
- GI disturbances –> could develop IBS
- can form reactive oxygen species
SULFUR:
- present in which amino acids?
- component of what essential compound?
- sources?
- EAR/RDA/UL?
- present in methionine, cysteine and cystine, in proteins
- component of glutathione (cysteine)
- sources = S-containing aa from protein digestion
- no intake requirement established bc sufficient sulfur intake from s-containing aa BUT plant proteins might not have enough s-containing aa which would decrease glutathione
