Dietary Ca2+

Question 1

Most abundant mineral in body

Answer 1

Ca2+
1200-1500g

(require >100mg/d)

Question 2

Mineral that actually mineralizes bone

Answer 2

Ca Hydroxyapatite

Question 3

General metabolic fxn of extracellular Ca2+

Answer 3

1. most common signal transmitter in bio
2. Tertiary structure: activate catalytic and mech. properties
3. Clotting, nerve impulse transmission/relaxation, mediation of hormones, growth factors

Question 4

↓ serum [Ca2+] effects on PTH and Vit D

Answer 4

↑ PTH →
bone resorption of Ca2+
- Ca excretion, ↑ excretion via kidney

↑ VIt D →
↑ Ca intestinal absorption
↓ Ca excretion in urine

Question 5

↑ Serum [Ca2+] effects on calcitonin, PTH, Ca reabsorption

Answer 5

↑ calcitonin
↓ PTH
↓ Ca reabsorption in ascending loop of henle

Question 6

active form of Vit D

Answer 6

1,25(OH)2D3

Question 7

Ca2+ absorption in Duodenum and reabsorption of Ca2+ in distal nephron involves active Vit D binding to what?

Answer 7

1,25(OH)2D3 binds to VDR → dimerizes with RXR → activates VDRE → upregulates gene transcription, which helps increase Ca2+ absorption

Question 8

↑ Ca intake (chronic) is associated with bone growth how?

Answer 8

↑ bone accretion (growth)

if you have limited intake, then you are going to have upregulation of Ca2+ to compensate

Question 9

Ca2+ absorption is enhanced by (2)

Answer 9

Vit D → synthesis of Ca transport proteins in prox small intestines

Increased physiologic demands (pregnancy, adolescence)

(NOT by bone mineral depletion)

Question 10

Ca2+ absoprtion is enhanced by bone mineral depletion true or false?

Answer 10

false

Question 11

Ca2+ absorption is impared by (2)

Answer 11

Vit D deficiency
- northern latitudes, limited skin exposure, dark pigmentation, elderly

Steatorrhea (fat malabsorption): unabsorbed FA binds Ca2+ → soaps

Question 12

Vast majority of Ca Incorporation into bone is by ______

Answer 12

endochondral bone formation

*cartilage backbone becomes mineralized

Question 13

Your entire skeleton turns over every ____ years

Answer 13

10!

Question 14

How much does the average healthy adult absorb Ca2+? Fetus in 3rd trimester (35 weeks)?

Answer 14

25%

fetus 80% in 3rd trimester, needs to form dem bones

Question 15

Concerns in preterm infants without adequate Ca2+ intake? Older children?

Answer 15

preterm infants:
Osteomalacia of prematurity

Older children:
Ca2+ deficient rickets

Question 16

Calcium absorption and retention is highest in _____ (time)_____. As you move farther away _______, bone mineralization slows.

Answer 16

early puberty
(massive amt of Ca2+ directly into her bone)

throughout adolescence

Question 17

During pregnancy (and other imp stages throughout life) _______ but not ______ requirements increase.

Answer 17

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

Question 18

Where do we get Ca2+ from food?

Answer 18

1. Dairy#1

2.

Question 19

When should they take calcium carbonate vs calcium citrate malate?

Answer 19

calcium carbonate
- best absorbed with meals

calcium citrate malate
- best absorbed between meals

Question 20

Risk of Ca supplements?

Answer 20

↑ risk of MI if they dont actually need them

Question 21

High risk groups for Ca2+ and Vit D deficient

Answer 21

1. premature infants
2. adolescents
3. peri-menopausal women
4. Bariatric surgery (duodenum is no longer connected to food matrix)

Question 22

Osteoporosis (3)

- how many women dev. it?

Answer 22

• 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

Question 23

Non nutritional factors that are associated with Osteoporosis (low bone mineral density)

Answer 23

1. Initial bone mineral density (hereditary)
2. Hypogonadism (low Estro)
   - E nl upreg false ligand and decreases osteoclastic act.
   - increase osteoclast apoptosis
3. Age
4. meds
   - glucocorticoids (block vit D)
   - steroids
5. behaviors/lifestyle
   - excess tobacco+alcohol

Question 24

Strongest empiric predictor of BMD

Answer 24

age

Question 25

Effects of weight bearing exercise?

Answer 25

double +

muscle mass directly related to bone mass

• increase osteocyte and osteoblast activity

Question 26

Nutritional factors associated with bone mineral density

Answer 26

1. lifetime ca2+ intake
2. Vit D
   - if ↓ intake then you get ↓Ca abs.
3. caffeine
   - ↑ urine [Ca2+] bad
4. protein intake
   - ↑ intake = ↑ abs Ca + ↑ urine Ca
5. sodium intake
   - ↑ intake = ↑ urine Ca
6. vegetarian
   - ↓ urine [Ca2+] good!