Calcium Flashcards
What are the macro minerals?
Calcium Magnesium Phosphorus Sodium Potassium Chloride
Why are macro minerals titled “macro”?
Because they are required in amounts greater than 100 mg/day
What are the micro minerals?
Iron Copper Zinc Selenium Chromium Iodine
What are sources of calcium?
Sardines
Dairy
Green leafy vegetables (kale)
Tortillas
How is calcium transported?
TRPV6
Transient receptor potential Vanilloid 6 (V6) (in intestine)
Does calcium need calbindin and TRPV 6 to absorb calcium?
No.
How is calcium absorbed?
It can be absorbed by para cellular diffusion (between cells).
Does not need a transporter to do this.
How is calcium absorption more efficient when consumed?
If calcium is consumed in divided doses through out the day.
What are factors that influence the absorption of calcium?
Vitamin D
Hormonal status (estrogen increases calcium absorption)
Dietary calcium
-a low calcium intake will increase calcium absorption
-a prolonged calcium deficiency will cause bone loss in order to maintain serum calcium levels and it is not corrected by an increase in absorption efficiency.
What are nutrients or substances that can enhance calcium absorption?
Vitamin D
Sugars and sugar alcohols
Protein
nutrients or substances that inhibit calcium absorption?
Fiber Phytate Oxalate Excessive divalent cations (Zn, mg) Unabsorbed fatty acids
What are nutrients that enhance urinary calcium excretion?
Sodium
Protein
Caffeine
Excessive calcium may inhibit the absorption of which nutrients?
Iron
Fatty acids
What phytate look like?
It has a lot of phosphate groups on it.
What is phytate?
It is the ,aim storage form of phosphorus in plants, mainly bran and seeds
What is phytates importance to calcium?
It binds ca2+ and reduces its bioavailability
Binds because phosphate is negative and calcium is positive
Where is oxalate found?
Found in green leafy vegetables, fruits, nuts, tea
What does oxalate do to calcium?
Binds Ca 2+ and reduces its availability
What is the key dietary factor that influences urinalysis calcium loss?
Dietary sodium
1 gram of sodium = 26 mg Ca lost in urine in adults
Where is calcium in the body?
In your bones and teeth
What is calciums abundance like?
It is the most abundant divalent cation in the human body.
How is calcium transported?
50% is free Ca2+
40% bound to protein such as albumin or prealbumin
10% is complexed with citrate, phosphate, sulfate
What is Calcium required for?
Nerve and muscle cells
Blood clotting
Enzymes as a cofactor
Blood calcium homeostasis is regulated by what?
PTH, calcitriol, calcitonin
Blood calcium is regulated between what values?
From 9-11 mg/100 ml
What is calcitonin?
It inhibits osteoclasts and prevents Ca2+ mobilization or resorption from bone
How does calcitonin affect blood calcium?
It reduces blood calcium concentrations
Where is calcitonin released?
Thyroid glands release the hormone calcitonin.
What hormone acts the opposite to PTH?
Calcitonin
How is calcium related to vitamin K?
It is necessary for some of the clotting factors
Calcium excretion
Most calcium is reasoned by the kidney
You still lose 100-240 mg Ca in urine each day
Fecal losses are 45-100 mg/day
What increases calcium fecal losses?
Phytate, oxalate, phosphorus
What affects Ca urinary losses?
PTH- decreases losses
sodium- increases losses
Caffeine
Intracellular Ca rises in response to what?
Cell activation via electrical, chemical, or physical stimuli.
There is usually more calcium intra or extracellularly?
Extracellularly
There is 10,000 fold less intracellularly.
Where are calcium selective channels found?
Found in plasma membrane of presynaptic nerve terminals
What is Priatt?
Ca channel inhibitor.
Comes from venomous snails.
How is calcium released intracellularly?
- Neurotransmitters and hormones bind to go receptors to trigger a series of events that lead to calcium release.
- Hydrolysis of cell membrane phospholipids.
- IP3 acts as a second messenger to trigger the release of calcium from the ER
- Calcium alone or bound to proteins like calmodulin will activate or deactivate enzymes through phosphorylation.
- PKC associates with DAG and free calcium to phosphorylate a variety of proteins or enzymes in the cell.
What is bone remodeling?
Continuous cycle throughout life that does not apply to teeth.
It is initiated by osteoclasts (bone resorbing cells).
It is controlled by osteoblasts.
Bone growth and remodeling levels in adolescence and adults?
Youth: resorption = redoposition
Period of
ADULTS: resorption > redoposition ( extreme form leads to osteoporosis)
How to determine calcium status?
Plasma Ca not useful
Can assessed by changes in bone density
(DEXA) dual energy x-Ray absorptiometry
Calcium deficiency results from?m
Inadequate intake of calcium
Poor calcium absorption
Excessive Ca losses
Where is Calcium deficiency clinically seen in?
Patients with rickets, tetany (intermittent muscle contractions), and osteoporosis
Calcium deficiency mainly effects?
Bone and muscle
What is osteoporosis?
Literally means “porous bones” resulting from reduced bone mineral density
There is a metabolic bone disorder
-decreased bone density and bone mass
-increased fractures
Bone resorption > bone formation
-decreased total bone mass
What are the parts of the bone that are more susceptible to bone loss in osteoporosis?
The trabecular bone is affected more than the cortical bone.
What are risk factors for osteoporosis?
Being female
-have more accelerated bone loss and 25% less bone mass
Being Caucasian
-blacks have 10-15% more bone mass
Small body size
-petite frame size at greater risk
Family history
Diseases that affects PTH, kidneys, GI, and liver (affects vitamin d)
Caffeine: risks double with >3.5 cups/day or>7 cups of tea
Smoking
-smaller body size for smokers
How to reduce risk for osteoporosis?
Achievement of optimal bone mass - maximize bone loss later in life Prevention throughout the lifecycle Reduce bone loss later in life (physical activity, esp. Weight bearing exercise.) Take in lots of Vitamin D
How does menopause affect bone loss?
During menopause there is less estrogen. Estrogen increases osteoclasts apoptosis, which leads to less bone resorption and less osteoblasts apoptosis. (Spares bone)
Without estrogen during menopause the rate of bone loss spikes up.
What is hormone replacement theory?
Decreases bone loss in post menopausal women.
Estrogen + Calcium treatment is much more effective than just estrogen.
What is the amount of calcium you should take each day?
AI = 1300mg/day
What population group might have a problem getting their AI for calcium?
Vegetarian or vegan because calcium is found in dairy or sardines
