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Flashcards in Ca and bone health Deck (32):

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

1. 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



Sx of hypocalcemia

tetany, muscle spasm, seizure


Conditions which can lead to hypocalcemia

1. 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

1. 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


Outcomes of osteoporosis

25% of older persons w/ hip fracture die within first year from fracture related complications


who is at risk for osteoporosis

Adolescents who become pregnant- the risk is greater if they do not have an adequate diet. Mexican american women, low bone mineral density, hypogonadism, older age, meds (corticosteroids), lifestyles


Lifestyl factors that increase risk for osteoporosis

tobacco/alcohol increase risk. Weight bearing exercise decreases risk


Nutritional factors associated with osteoporosis

1. low Ca intake. 2. low Vit D intake. 3. low protein intake. 4. high salt intake. 5. low fruit/veg intake. 6. caffeine intake


Strategies to optimize bone density

Achieve “peak bone mass” when possible, consume enough Ca, Vit D, Vit K and protein, maintain ovulation/regular menses, weight bearing exercise, avoid smoking, alcohol, salt and steroids


Should people > 50 yr take Ca++ Supplements

YES! Supplements are associated with 12% risk reduction in fractures of all types and reduced rate of bone loss (hip > spine)


Medical conditions which increase risk of osteopenia

Chronic illnesses with malabsorption and/or chronic systemic inflammation. Crohns and UC: magnitude of steroid use is single strongest predictor of osteopenia. Obesity


risks of Ca supplementation

may be associated with increased risk of MI when taken without Vit D.