Calcium Flashcards
What is the RDA for 9-13 years?
1,300 mg calcium
What is the RDA for 14-18 years?
1,300 mg calcium
What is the RDA for 19-50 years?
1,000 mg calcium
What is the RDA for 0-6 months?
200 mg calcium
What is the RDA for 6-12 months?
260 mg calcium
What is the RDA for 51-70 years for women? For men?
Women: 1,200 mg calcium (due to the onset of menopause)
Men: 1,000 mg calcium
What is the RDA for 71+ years?
1,200 mg calcium for both men and women
Who established the RDAs for calcium?
FNB established the amounts of calcium required for bone health and to maintain adequate rates of calcium retention in healthy people
Build and maintain strong bones
Prevent loss of bone mass
Food sources of calcium
Dairy products: yogurt, mozzarella
Canned fish (packed with bones)
Tofu made with calcium sulfate
(TRUE/FALSE)
Calcium content varies slightly by fat content, the more fat, the less calcium it contains.
TRUE
(TRUE/FALSE)
Calcium content for tofu is processed with a calcium salt. Tofu processed with other salts does not provide significant amounts of calcium.
TRUE
(TRUE/FALSE)
Calcium is absorbed very well.
FALSE
Unfortunately, calcium is NOT very well absorbed at all, and there are several dietary factors that can inhibit calcium absorption.
What are some dietary factors that inhibit calcium absorption?
How do they inhibit absorption?
-Phytic acid
-Oxalic acid
-Any kind of unabsorbed FAs (which would probably be secondary to some type of GI chronic condition, like Crohn’s disease)
-Insoluble fiber
They bind calcium to be excreted via feces
What are the 3 forms of calcium in the blood?
- Free Ca2+
- Protein-bound calcium (prealbumin or ALBUMIN) — the majority will be bound to albumin
- Nonprotein-complexed calcium (but complex with citrate, sulfate, or phosphate)
Phytic acid
The stored form of phosphorus, found in beans, legumes, seeds, nuts, and unprocessed whole grains (outer bran layers)
TRPV6
Transporter; Calcium-channel TRPV6 located on the brush border membrane of the enterocytes.
How the majority of calcium enters the enterocytes
What ways can calcium enter the enterocytes?
- TRPV6 transporter (majority)
- Paracellular diffusion (only during times of high calcium concentrations in the intestines)
Calbindin
An important protein that will bind up calcium, once it enters the enterocyte, chaperoning it across the enterocyte, so that it can be pumped out of the enterocyte, and into the blood
(TRUE/FALSE)
Vitamin D increases the absorption of calcium.
TRUE **
How does vitamin D increase the absorption of calcium?
It can increase the expression of the TRPV6 and CALBINDIN
*These 2 proteins are very important, and the expression of these proteins is highly regulated by vitamin D.
What 2 ways can calcium leave the enterocyte during absorption?
- Calcium ATPase transporter (PMCA1b)
- Sodium calcium exchanger (NCX1) pump
Exit the enterocyte and enter the blood
(TRUE/FALSE)
Pectin does affect calcium absorption.
FALSE
only insoluble fiber
What are some enhancers for calcium absorption?
Vitamin D (regulates transporter & calbindin)
Vitamin C
Lactose in breast milk (increases bioavailability)
How much of the calcium in blood is going to be bound to albumin?
~90% of protein-bound calcium, will be bound to albumin
The remaining 10% will be bound to a variety of globulins
(TRUE/FALSE)
Calcium is the most abundant mineral element found in the body.
TRUE
What % of the 1200g of calcium in the adult is in the form of hydroxyapatite in the skeleton?
98%
Calcium hydroxyapatite is made up of what?
Calcium and Phosphorus
What gives bones the rigidity and the hardness?
Phosphorus
Trabecular bone
Losses here are reflective of insufficient calcium in the diet and early on during menopause.
Cortical bone
Can see it being broken down after the age of 65, this is secondary to the trabecular bone
Which early on losses of XXXX bone are evident in osteoporosis?
Trabecular bone when there is insufficient calcium in the diet; seen in the menopausal phase
Cortical bone is secondary
Which bone loss is a result of those vertebral fractures that are seen with aging and in younger individuals, less than 65 years old?
Trabecular bone
In older adults, 65 years and up, it is what type of fractures that is associate with these cortical bone fractures due to this type of bone loss in the cortical bone resulting in breaks?
Hip fractures
What are the functions of calcium?
- Bone
- Muscle contraction
- Cell signaling
- Coenzyme
- Nervous system
- Calcium homeostasis
How does calcium play a role in cell signaling?
The typical function of calcium is that it binds to a protein, CALMODULIN
The activation of calmodulin by calcium plays a very important role, in terms of, insulin signaling and glucose metabolism
How does calcium play a role as a coenzyme?
It was calcium that was able to bind up to those proteins that were carboxylated with Vitamin K dependent GAMMA GLUTAMYL CARBOXYLASE.
So, in terms of being a coenzyme, calcium is important in the intrinsic pathway and the extrinsic pathway.
There are a handful of different types of enzymes that are regulated by calcium directly or via the binding of calcium to that CALMODULIN protein.
So, overall without calcium many reactions would not be able to progress forward.
Explain how calcium plays a role in the nervous system.
- An action potential (stimulus) depolarizes the axon terminal.
- The depolarization opens voltage-gated calcium channels and calcium enters the cell.
- Calcium entry triggers EXOCYTOSIS of synaptic vesicle contents
- Neurotransmitter diffuses across the synaptic cleft and binds with receptors on the postsynaptic cell.
(TRUE/FALSE)
Imbalance in blood calcium levels can result in delirium and confusion.
TRUE
Osteoporosis
A disorder characterized by porous and fragile bones.
A serious health problem for more than 10 million US adults; 80% are women and post-menopausal
What fractures are the most commonly associated with osteoporosis?
- Fractures to the vertebrae are the most common osteoporotic fx
- Hip fractures, next
- Wrist/forearm (radius bone), third
1.5 million fractures occur each year in the US due to osteoporosis
Osteopenia
Meaning low bone mass
34 million people have it, it precedes osteoporosis
How does menopause lead to bone loss?
The decrease in estrogen production:
-Both increase bone resorption and decreases calcium absorption
How much bone mass XX% per year frequently occurs with menopause?
3-5% per year
Then, less than 1% after the age of 65
What is the best way to prevent osteoporosis?
Increase in bone mass density early on in life.
Some research is showing some benefit to calcium & vitamin D supplementation in post-menopausal women
Toxicity of calcium, causes what?
Hypercalcemia
When does toxicity of calcium happen?
It has not been associated with over consumption of calcium, naturally occurring in food
ONLY from the consumption of large quantities of calcium SUPPLEMENTS in combination with ANTACIDS
(TRUE/FALSE)
Back in the day, peptic ulcers were treated with large quantities of milk, calcium carbonate (antacids), and sodium bicarbonate, which led to hypercalcemia.
TRUE
Calcium supplement levels from 1.5 to 16.5 g/day for 2 days to 30 years.
What is the normal range for calcium?
8.5 to 10.5 mg/dL (adult values)
In terms of calcium distribution in the human body, where is the vast majority stored?
98.9% as the hydroxyapatite form; FOUND IN THE BONE.
How much of total body calcium is present in cells?
1%
-50% (1.2 mmol/L) is free calcium
-41% (1.2 mmol/L) is protein-bound calcium (90% of this is bound to albumin)
-9% (0.2 mmol/L) is anion-bound calcium
How much of total body calcium is present in the extracellular fluid?
0.1%
Where is ionized calcium (Ca2+) found?
Of that 1% of the calcium found in cells, about 50% or 1.2 mmol/L will be present as FREE CALCIUM or ACTIVE
It CAN diffuse EASILY across the capillary membranes
Where is the protein-bound calcium found?
Of that 1% of the calcium found in cells, about 41% or 1.2 mmol/L will be mainly BOUND TO ALBUMIN, therefore
It cannot diffuse across capillary membranes
Where is anion-bound calcium found?
Phosphate and citrate-bound calcium
It CAN diffuse EASILY across the capillary membranes
