Ca and bone health Flashcards
Absorption of Ca- where does it occur and how
Occurs passively in duodenum, jejunum, ileum when Ca intake is high; Active transport (effected by habitual intake via vitamin D) occurs in the duodenum when Ca intake is low/moderate.
How does Ca intake correlate with absorption
increased Ca intake leads to increased bone accretion.
Calcium absorption is enahced by _____________
Vitamin D, increased demand (pregnancy, adolescence), lactose (maintains solubility), gastric acidity, dietary protein
Ca absorption is impaired by _____________
Vit D deficiency, steatorrhea (F.A. bind Ca and form soaps), oxalic acid (spinach), phytic acid (legumes, soy beans, corn, wheat), gastric alkalinity
Excretion of Ca
regulated in kidney- can reabsorb or excrete Ca depending on hormonal signals
Ca deficiency
Is rare b/c the body is able to maintain serum levels. It can develop over time though thus it is a long term, silent process.
List critical stages of life for Ca intake
- premature infants. 2. adolescence. 3. peri-menopause and after skeletal maturity. 4. pregnancy and lactation. 5. post-bariatric surgery
Premature infants and Ca intake
There is a 3rd trimester period of rapid bone mineral accretion; preterm infants at risk for “osteopenia of prematurity
Adolescence and Ca intake
Hormones during puberty favor Ca absorption and bone deposition. 50% of total adult bone mineral mass is accrued during adolescence. Ca absorption and retention is highest in early puberty.
Ca intake after skeletal maturity
Associated with relatively high requirements, increased losses, and frequently with low intake
Ca intake and pregnancy/lactation
Physiologic responses compensate for increased Ca demand so dietary requirements are not increased
What proportion of bone mineral density is due to genetics
60-80%
Sx of hypocalcemia
tetany, muscle spasm, seizure
Conditions which can lead to hypocalcemia
- life stages: premature infant, lactating adolescent, elderly (poor absorption). 2. pathological: Vit D deficiency, hypoparathyroidism, bariatric surgery
How does the recommended daily intake of Ca change over the course of a persons life
The DRI is highest during adolescence, post-menopausal women, all people >70, pregnancy/lactating adolescent
How does Ca RDA change during pregnancy/lactating (non-adolescent)
Physiological but not dietary requirements increase. During pregnancy, Ca absorption increases (active) to accommodate fetal demand. During lactation, PTH increases and bone mass is lost, but it is recovered by 6-12 months post-weaning
Which foods have highest calcium
diary > salmon > tofu > greens > broccoli
How does average Ca intake compare with RDA
Adolescent females and the elderly are not consuming enough Ca on average
Ca supplements
- Calcium carbonate (eg. TUMS)- best absorbed with meals. Has maximal elemental Ca per tablet and the least lead. 2. Calcium citrate malate- best absorbed between meals.
How does Na affect Ca levels
Na intake increases Ca excretion in urine
Which diet may improve serum Ca levels
DASH diet- reduction of Na decreases urine Ca and may have benefits to long term bone status. This diet also incorporates more Ca into it than traditional US diets
How does Protein affect Ca levels
Increased protein intake correlates with increased absorption of Ca and increased urine Ca, so net effect is neutral or positive
How does caffeine affect Ca levels
increases urine Ca excretion
What happens if we don’t get enough Calcium?
Short term: Metabolic Regulation. Long term: Bone mineral depletion
