Nutrition and Osteoporosis Flashcards
2 diff tissue types in bone
cortical (80%) and trabecular (20%)
bone is organic matrix composed of ___ fibres with _____ salt deposits and crystallized ____ ions
collagen; calcium and phosphate; hydroxyl
bones help maintain _____ in the ECF
physiologic concentrations of P and Ca
calcium content in the body totals ___ g and hydroxyapatite makes up ___% of total available calcium
1100-2000; 99
where is the remaining 1% of Ca?
in ECF an regulates various biochem events
normal serum concentration of Ca (total):
2.1-2.5 mmol/L
normal serum concentration of P:
0.8-1.5 mmol/L
P content in body totals ___g and ___% found in bones
500-800; 85-90
maintaining Ca and P homeostasis is complex cuz requires balance of:
diet intake, fecal/urinary losses, flux in/out of bone
primary hormones involved in Ca and P regulation:
PTH and vit D (calcitriol)
other hormones involved in Ca and P regulation:
calcitonin, cortisol, growth and thyroid hormone
how does PTH work?
stim osteoclasts (bone remodelling, urinary loss of calcium)
most common bone disease in humans characterized by decreased bone density, deteriorations of bone microarchitecture (qualitY)
osteoporosis
osteoporosis ^ susceptibility to:
fractures, pain, morbidity
first step on way to osteoporosis:
osteopenia (low bone mass)
2 types of primary osteoporosis:
type 1 estrogen-androgen deficient OP, type 2 age-related OP
what is type 1 primary>
occurs in women within few years of menopause from loss of trabecular (spongy) bone tissue and cessation of ovarian production of estrogen
what is type 2 primary?
occurs >70 yrs, hormonal regulatory processes that govern bone remodelling gradually change in ageing so imbalance tween bone formation and resorption occurs (uncoupling)
secondary OP occurs in relation to:
drugs or med conditions that ^ bone loss
risk factors for osteoporosis:
Caucasian/Asian, small body size and thin bones ,low BMD, personal hx fracture after age 50 (or in parent/sibling), age 65+, abnormal absence of menstrual periods, low estrogen, low testosterone, glucocorticoid therapy > 3 months, alcoholism, low lifelong Ca and D intake, physical inactivity, poor health/frailty, current smoking
risk factors relate to:
development of peak BMD, remineralization/demineralization once peak BMD achieved
diseases associated with ^ risk of osteoporosis:
GI, genetic, endocrine, hypogonadal states, miscellaneous
drugs associated with ^ risk osteoporosis:
glucocorticoids, anticonvulsants, barbiturates, heparin, lithium, methotrexate, PPI, SSRI, thiazolidinediones
BMD best measured using ____ and results compared to ____ diagnostic T score criteria
DXA; WHO
T score shows:
how much measured BMD is higher or lower than BMD of a healthy 30 year old adult
normal T score is ___, low BM is ____, osteoporosis is ____ and severe is ____
-1 or greater; between -1 and -2.5; -2.5 or less; -2.5 or less with 1+ fractures
key nutrients of consideration are:
calcium, vit D, protein, sodium, caffeine
other nutrients and food comps important:
P (essential for normal bone structure and function), trace minerals, vit A, Vit K (help develop and maintain bone), fibre, alcohol, soy
when ingested in excess, these nutrients and food comps adversely affect bone metabolism:
vitamin A (UL 3000mcg retinol), sodium (UL > 2300mg), alcohol, caffeine
primary bone forming mineral that is required for achieving peak bone mass, maintaining bone mass, minimizing bone mineral loss, decreasing incidence of OP related fractures
Ca
decreased Ca intake –> ___ serum Ca –> ____ PTH –>stimulate bone ____ to ____ serum Ca
decreased; increased; resorption; increase
DVs assume ____ mg/day for Ca
1100
primary function of vitamin D:
^ serum Ca and P concentrations via promotion of absorption via GIT, promoting reabsorption by kidney, stem osteoclast function (bone resorption)
serum ____ is a good indicator of vitamin D status total body stores
25-hydroxycholecalciferol
reference values for vit D deficient ___, relative insufficient___, optimal ___, toxic ____
<25; 25-70; 70-250; >250 (nmol/L)
what is the RDA for most life stage/gender groups:
15 mcg or 600 IU
what is RDA for vit D for adults 70 yrs +?
20 mcg or 800 IU
bone strength is due to:
cable like tensile strength from collagen, hardness from hydroxyapatite
trabecular bone predominantly in ______ and is less dense than cortical
knobby ends of long bones
trabecular bone is exposed to ____ and lined by more cells than cortical, it is more responsive to factors like _____
circulating fluids from bone marrow; estrogen
which type of bone loss is largely responsible for occurrence of fractures (esp spine)?
trabecular
cortical bone contains ____ that run parallel with shaft axis
osteon (vertical Haversian systems)
what is in centre of each osteon?
canal that contains artery that supplies bone tissues with nutrients and O2, vein for removing wastes, nerve for returning afferent relays to brain
what is BMC?
bone mineral content; measurement of bone mineral found in a specific area, measured in grams
what is BMD?
bone mineral density; describes mineral content of bone per unit/area of bone, measured in g/cm^2 (ie. BMC/bone area)
osteoclasts in charge of ___, osteoblasts in charge of _____
bone breakdown/resorption via enzymes and acid; bone formation, synth matrix proteins (osteocalcin, collagen type 1), bone mineralization, lining cells (regulate passage of Ca in/out of cell, respond to hormones by synth proteins that activate osteoclasts)
what are osteocytes?
cells inside bone that are derived from osteoblasts that sense pressures/cracks in bone are to direct where osteoclasts dissolve the bone
what is bone reabsorption?
resorption of bone tissue , process by which osteoclasts break down tissue in bones and release the minerals, resulting in transfer of calcium from bone tissue to blood
osteoclasts and osteoblasts communicate via:
cytokine signalling
term applied to the growth of the skeleton until mature height is achieved
bone modelling
bone modelling is done at age ___ in F and ____ in M
16-18; 18-20
amount of bony tissue present at end of skeletal maturation
peak bone mass (around age 30)
what influences peak bone mass?
diet, physical activity, race, genetics
process by which bone mass continues to accumulate after bones stop growing at 18-20 years:
consolidation (filling in of osteons in shaft of long bones)
what is the major physiological effect of estrogen?
inhibit bone resorption
process in which bone is resorbed continuously thru osteoclast action and reformed thru action of osteoblasts
bone remodeling
process of bone remodelling:
activated by preosteoclatic cells in bone marrow, cytokines released from bone-lining cells which trigger activity of precursor stem cells in bone marrow–>preosteoclatic cells migrate from bone marrow to bone surfaces while differentiating into mature osteoclasts –>cover specific area of bone tissue and release acids and proteolytic enzymes which form small cavities on surface of bone and resorb bone mineral and matrix on surface of bone–>rebuilding/formation involves secretion of collagen and other matrix proteins by osteoblasts–>collagen polymerizes to form mature triple stranded fibres and other matrix proteins secreted –>salts of Ca and phosphate begin to precipitate on the collagen fibres developing into the hydroxyapatite-
resorption is ___ and refilling is ___
fast (days); slow (months)
major sources of P
high protein foods, whole grains, processed foods
why concern about diet high in P and low in Ca?
cuz impair usual homeostatic mechanisms that come into play when diet Ca is limited (focus on P rich carbonated beverages), but not proven experimentally and negligible effect on Ca excretion
consume up to __mg of caffeine
400
why is their prob with using coffee as surrogate for caffeine?
confounding factors in coffee, don’t define how big a cup of coffee is, how much caffeine in cup of coffee depends on type brewed, what is put in it
theories of protein influence on OP:
OP and hip fractures common in countries with excess meat and dairy consumption (correlation); high protein diets are high acid so ^ Ca excretion and might have deleterious effect on bone (but sci not support theories, actually ^ protein might have + effect on bone)
positive effect of high protein intake:
muscle health and strength reduce fall and fracture risk, a.a. for bone matrix, ^ intestinal Ca absorption, increase in circulating IGF-1, decrease serum PTH
high Na causes ______
increased urinary Ca excretion
why OP common in chronic alcoholism?
nutrient displacement (poor Ca and vit D intake), ^ PTH, toxic effect on osteoblasts, increase risk of falls
why physical activity good for bone?
regular wt bearing and muscle strengthening exercise slows rate of bone loss, increase BMD, reduce fall risk, protect spine
in assessment, should get these anthropometrics:
ht, wt, bone structure, wt history, BMI
in assessment, get these biochem/med tests:
vitamin D (total, 25-hydroxy), DXA bone density
in assessment, get these clinical (client hx and NFPE):
age, sex, gender, smoker, PA, med history, meds, overweight/obese, frailty, kyphosis
in assessment , get these dietary:
vit D, Ca, protein, Na, caffeine, alcohol, supplements, food and nutrition related attitudes
common nutrition probs in osteoporosis:
inadequate vit D and/or Ca intake, altered GI function, predicted food/med interaction, malnutrition, excess alcohol, food and nutrition related knowledge deficits, physical inactivity
for adults 50+ yrs, calcium should be ____mg and vit D for adults at moderate risk should be _____IU
1200; 800-2000
Ca supplements may ^ risk for ___
MI
acute ^ in serum Ca (supplements) may contribute to _____
vascular calcification (deposit of calcium phosphate into CV structures) –>predictive biomarkers of CVD, ^ blood coagulation, ^ arterial stiffness
clinical approach to Ca supplementation :
individualized, complete diet hx/calcium calculator, counsel to meet Ca requirements via diet but if not achievable consider supplement of no more than 500mg/day, educate on risks and benefits, liaise with physician
most common Ca supplement that is least expensive and needs to be taken with meals and interferes with iron absorption
calcium carbonate
type of Ca supplement can be taken any time:
Ca citrate
considerations for pt and clinicians when supplementing :
cost, form, non medicinal ingredients, taste/tolerance/side effects
antiresorptive drugs:
bisphosphonates (bind to surface of bones to slow down resorbing, don’t take with food or supplements), RANK ligand inhibitor (inhibit development and activation of osteoclasts, injection)
hormone therapies:
estrogen +/- progesterone , PTH therapy (bone formation therapy–>activates osteoblasts), SERMS (selective estrogen receptor modulators, non-hormonal and blocks effects of estrogen in uterus and breast, used for ppl with high cancer risk), calcitonin (slows down osteoclast activity)
