Dietary Ca2+ Flashcards
Most abundant mineral in body
Ca2+
1200-1500g
(require >100mg/d)
Mineral that actually mineralizes bone
Ca Hydroxyapatite
General metabolic fxn of extracellular Ca2+
- most common signal transmitter in bio
- Tertiary structure: activate catalytic and mech. properties
- Clotting, nerve impulse transmission/relaxation, mediation of hormones, growth factors
↓ serum [Ca2+] effects on PTH and Vit D
↑ PTH →
bone resorption of Ca2+
- Ca excretion, ↑ excretion via kidney
↑ VIt D →
↑ Ca intestinal absorption
↓ Ca excretion in urine
↑ Serum [Ca2+] effects on calcitonin, PTH, Ca reabsorption
↑ calcitonin
↓ PTH
↓ Ca reabsorption in ascending loop of henle
active form of Vit D
1,25(OH)2D3
Ca2+ absorption in Duodenum and reabsorption of Ca2+ in distal nephron involves active Vit D binding to what?
1,25(OH)2D3 binds to VDR → dimerizes with RXR → activates VDRE → upregulates gene transcription, which helps increase Ca2+ absorption
↑ Ca intake (chronic) is associated with bone growth how?
↑ bone accretion (growth)
if you have limited intake, then you are going to have upregulation of Ca2+ to compensate
Ca2+ absorption is enhanced by (2)
Vit D → synthesis of Ca transport proteins in prox small intestines
Increased physiologic demands (pregnancy, adolescence)
(NOT by bone mineral depletion)
Ca2+ absoprtion is enhanced by bone mineral depletion true or false?
false
Ca2+ absorption is impared by (2)
Vit D deficiency
- northern latitudes, limited skin exposure, dark pigmentation, elderly
Steatorrhea (fat malabsorption): unabsorbed FA binds Ca2+ → soaps
Vast majority of Ca Incorporation into bone is by ______
endochondral bone formation
*cartilage backbone becomes mineralized
Your entire skeleton turns over every ____ years
10!
How much does the average healthy adult absorb Ca2+? Fetus in 3rd trimester (35 weeks)?
25%
fetus 80% in 3rd trimester, needs to form dem bones
Concerns in preterm infants without adequate Ca2+ intake? Older children?
preterm infants:
Osteomalacia of prematurity
Older children:
Ca2+ deficient rickets
Calcium absorption and retention is highest in _____ (time)_____. As you move farther away _______, bone mineralization slows.
early puberty (massive amt of Ca2+ directly into her bone)
throughout adolescence
During pregnancy (and other imp stages throughout life) _______ but not ______ requirements increase.
Physiological, but not dietary
- Ie: Ca2+ absorption increases (active) to accomodate fetal demand
- you dont got to do nothing, body does it all for you
Where do we get Ca2+ from food?
- Dairy#1
2.
When should they take calcium carbonate vs calcium citrate malate?
calcium carbonate
- best absorbed with meals
calcium citrate malate
- best absorbed between meals
Risk of Ca supplements?
↑ risk of MI if they dont actually need them
High risk groups for Ca2+ and Vit D deficient
- premature infants
- adolescents
- peri-menopausal women
- Bariatric surgery (duodenum is no longer connected to food matrix)
Osteoporosis (3)
- how many women dev. it?
- Reduction in bone mass assoc. w/ impairment in bone structure
- ↑fracture risk
- loss of height and distorted body shape
*25% of women>50 yrs old dev. osteoporosis
Non nutritional factors that are associated with Osteoporosis (low bone mineral density)
- Initial bone mineral density (hereditary)
- Hypogonadism (low Estro)
- E nl upreg false ligand and decreases osteoclastic act.
- increase osteoclast apoptosis - Age
- meds
- glucocorticoids (block vit D)
- steroids - behaviors/lifestyle
- excess tobacco+alcohol
Strongest empiric predictor of BMD
age
Effects of weight bearing exercise?
double +
muscle mass directly related to bone mass
- increase osteocyte and osteoblast activity
Nutritional factors associated with bone mineral density
- lifetime ca2+ intake
- Vit D
- if ↓ intake then you get ↓Ca abs. - caffeine
- ↑ urine [Ca2+] bad - protein intake
- ↑ intake = ↑ abs Ca + ↑ urine Ca - sodium intake
- ↑ intake = ↑ urine Ca - vegetarian
- ↓ urine [Ca2+] good!
