Calcium Flashcards
How is calcium most efficiently absorbed
Vitamin D/saturable (limited amount of Calbindin)
How is calcium absorbed without VitD
paracellular diffusion/nonsaturable; ability increases as saturation of Calbindin occurs
What nutrients Enhance Calcium absorption
VitD, sugar (lactose), Protein
Under what conditions does protein enhance Calcium absoprtion
High protein, low Calcium intake; regulated more by Ca intake
What nutrients Enhance urinary Excretion of Calcium
Sodium, Protein, Caffeine
What nutrients Inhibit Calcium absorption; How?
Fiber, Phytate, Oxalate(leafy greens), Unabsorbed FA, Zinc, Mg; Binding in Lumen
What nutrients does Calcium inhibit absorption of
Iron, Fatty Acids
What are sources of Calcium
Dairy, Broccoli, Leafy greens, Almonds
What is the RDA for Calcium 19-50years
1,000mg
What is the RDA for Calcium 51-71years for Men
1,000mg
What is the RDA for Calcium 51-71years for Women
1,200mg
What is the RDA for Calcium 71+years
1,200mg
What is the Natl Osteoporosis Found Calcium recommendation
Agree with RDA, >1200-155mg unlikely to benefit, may be harmful
What is the UL for Calcium
2,500mg
What can result from prolonged UL intake of Calcium
Calcium deposits in joints, kidneys
What are the supplement forms of calcium
Calcium carbonate (27%) and Calcium citrate-malate (35%)
What is the Calcium bioavailability of dairy products
29% (290mg/serv)
What is the Calcium bioavailability of spinach
5% (122mg/serv)
What is the Calcium bioavailability of bok choy
50% (79mg/serv)
What is the Calcium bioavailability of broccoli
57% (31mg/serv)
What is the Calcium bioavailability of almonds
20% (75mg/serv)
How is Calcium status measured
Mainly based on intake; Bone densitometry DEXA
Is serum Calcium a measurement of Calcium status
Not measured well in blood because highly regulated by hormones
What senses a drop in blood Calcium
Parathyroid gland
What is secreted when blood Calcium drops
Parathyroid Hormone (PTH)
What are the functions of PTH in Calcium homeostasis
Stimulates activation of VitD in the kidney (resorption of Calcium); Draws Calcium out of bone for use in blood
What senses an increase in blood Calcium
Thyroid gland
What is secreted when blood Calcium rises
Calcitonin
What hormone opposes PTH
Calcitonin
What does Calcitriol (VitD) bind to when entering enterocyte for Calcium absorption (Step 1)
VitD Receptor (VDR)
What is the next step for VitD after binding to VDR for Calcium absorption (Step 2)
VDR-Calcitriol complex binds to DNA in nucleus of the enterocyte
What is the next step for VitD after binding to DNA for Calcium absorption (Step 3)
Transcription of VDR-Calcitriol to form Calbindin-mRNA
What is the next step for VitD after transcription of Calbindin-mRNA in nucleus for Calcium absorption (Step 4)
Calbindin-mRNA Translation of Calbindin protein in cytosol
What is the next step for VitD after translation of Calbindin protein for Calcium absorption(Step 5)
Calbindin protein acts as a carrier for Calcium at the brush border of the enterocyte
How much Calcium can the lumen handle at a time
500mg
Why do Multivitamins usually contain small amounts of Calcium
Competes with Iron, Zinc and Magnesium and will make pill too large
How does Sodium effect Calcium absorption
Calcium is pulled along with Sodium during Sodium excretion
How much Calcium is lost (in urine/feces/skin) each day
250-300mg
How much Calcium needs to be replaced what is being lost (in urine/feces/skin)
250-300mg
Why is the RDA for Calcium so much higher than the amount needed to replace what is lost each day
Because of the poor bioavailabilty of Calcium; Based on bioavailability of Dairy products (29%)
