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CALCIUM. FCSFN 648. Introduction. Ca is the most abundant mineral in the body Ca (latin “calx” means limestone) was known as early as the first century when the Ancient Romans prepared lime as calcium oxide. Distribution & function in the body - bone . Over 99% Ca exists in the skeleton

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Calcium

CALCIUM

FCSFN 648


Introduction
Introduction

  • Ca is the most abundant mineral in the body

  • Ca (latin “calx” means limestone) was known as early as the first century when the Ancient Romans prepared lime as calcium oxide


Distribution function in the body bone
Distribution & function in the body - bone

  • Over 99% Ca exists in the skeleton

  • Structural role

  • Functional role

  • Castatus can be assessed by measuring BMC by bone densitometry


Distribution function in the body bone1
Distribution & function in the body - bone

  • Bone remodeling occurs throughout life

  • Bone formation is > than resorption during growth (especially adolescence)* in girls - 90% total BMC (17 y) & 99% (26 y)* boys - occurs 18.5 y

  • In W onset of bone loss occurs * 48 y (spine) & 37 y (femoral neck)

  • Maximal loss in W occurs * bet 54-58 (hips, spine etc)


Distribution function in the body bone2
Distribution & function in the body - bone

  • On average - bone Ca pool turns over every 5-6 y

  • 2 types of bones * cortical* trabecular

  • Cortical bone



Functions
Functions

  • Mineralization - bone & teeth

  • Blood clotting


Functions1
Functions

  • Other functions


Solubility
Solubility

  • Ca is absorbed only in ionized form (Ca+2)

  • Ca in food & dietary supplements - insoluble salts

  • Solubility - mildly acidic pH

  • Solubility doesn’t ensure better absorption

  • In alkaline pH, Ca may complex with minerals or other dietary components


Calcium location quantity
Calcium location & quantity

  • Average adult ~ 1 kg Ca (99% - skeleton)as calcium phosphate salts

  • ECF has ~ 22.5 mmol of which 9 mmol is inthe serum

  • Every 24 hours, 500 mmol Ca is exchanged bet bone & ECF


Normal ranges
Normal ranges

  • Normal serum levels (8.5-10.5 mg/dL)

  • Normal ionized level (4.5-5.6 mg/dL)

  • Amount of total calcium is dependent on albumin

  • Biologic effect of Ca is determined on the amount of ionized Ca rather than the total calcium


Corrected ca level
Corrected Ca level

  • Corrected Ca level is used when albumin is abnormal

  • Corrected Ca (mg/dL) = measured total Ca (mg/dL) + 0.8 (4.0 - serum albumin [g/dL]), where 4.0 represents the average albumin level

  • With hypoalbuminemia corrected level is higher than the total Ca


Absorption
Absorption

  • Absorption - Ca has to be in the ionized form

  • Generally 20-50% ingested Ca is absorbed

  • Amount of Ca absorbed depends

  • Intake


Absorption1
Absorption

  • Physiological factors


Absorption2
Absorption

  • Occurs along the length of the small intestine

  • Generally 2 routes of absorption

  • Other route of absorption


Saturable system transcellular
Saturable system (Transcellular)

  • This is active & saturable system (fig)

  • Takes place mainly in the duodenum & proximal jejunum

  • Occurs actively when Ca is in short supply (↓ dietary)

  • Ca moves from brush border into the enterocyte as unbound Ca+2

  • Ca+2 binds with intracellular protein (calbindin or CPB) which takes Ca+2 into the mitochondria & other subcell compartments

  • Ca+2 leaves the enterocyte in exchange for Naor by calcium activated ATPase


Saturable system transcellular1
Saturable system (Transcellular)

  • Saturable process occurs


Passive non saturable paracellular
Passive & Non-saturable (Paracellular)

  • This is passive & non-saturable system

  • Takes place mostly jejunum & ileum

  • Is dependent on vit D

  • Occurs passively when there is adequate dietary Ca

  • Ca enters into the enterocyte with the help of vit D


Colon
Colon

  • Bacteria in the colon releases Ca bound fermentable fibers

  • ~ 4% (~ 8 mg/d) of dietary Ca is absorbed by this route

  • Amount is higher in people who are unable to absorb more Ca from the small intestine


Factors that enhance ca absorption
Factors that enhance Ca absorption

  • ↑ lactose

  • ↑ vit D

  • ↑ acidic environment

  • ↓ stress

  • Distribution of Ca intake

  • ↑ physiological need


Absorption enhanced lactose
Absorption enhanced - lactose

  • From breast milk & formula

  • Infants fed lactose

  • Research - rats fed diets with differentCHOs, i.e. 25%* lactose, glucose, sucrose, maltose or starch* lactose only ↑ Ca absorption (Bergeim et al., 1926)


Absorption enhanced
Absorption - enhanced

  • Vitamin D

  • Acidic conditions

  • Lack of stress


Absorption enhanced1
Absorption - enhanced

  • Distribution of Ca intake

  • Increased physiological need


Factors that inhibit ca absorption
Factors that inhibit Ca absorption

  • Non-fermentable fibers

  • Phytate

  • Oxalate

  • Magnesium

  • Dietary fatty acids

  • Physical activity

  • Potassium


Factors that inhibit ca absorption1
Factors that inhibit Ca absorption

  • Non-fermentable fibers

  • Phytate

  • Oxalates


Factors that inhibit ca absorption2
Factors that inhibit Ca absorption

  • Magnesium

  • Dietary fatty acids



Transport
Transport

  • In the blood, Ca is transported in 3 forms* ~ 40% Ca is bound to protein mainly albumin* ~ 10% is complexed with sulfate, phosphate or citrate* ~ 50% of Ca is found free in blood (ionized Ca+2)


Storage
Storage

  • Skeleton is the major storage site* since ~ 99% of the body's Ca is in the bone

  • Short term

  • Long term, chronic removal of skeletal calcium


Excretion
Excretion

  • Primarily in the urine and feces

  • Urinary losses range from 40-200 mg/d occurs:

  • Urinary Ca excretion is ↓

  • Urinary Ca excretion is ↑


Excretion1
Excretion

  • Most Ca is filtered and reabsorbed by the kidneys


Excretion2
Excretion

  • Fecal losses range from 45-100 mg/d

  • ↑ fecal losses are ↑ with

  • Skin losses 60 mg/d


Regulation calcium balance extracellulary
Regulation - calcium balance (Extracellulary)

  • The level of ionized calcium in plasma is controlled by 3 factors:* PTH* Calcitonin* Calcitriol (1,25-(OH)2D3 ) (i.e. vit D)


Parathyroid hormone pth
Parathyroid Hormone (PTH)

  • ↓ in ECF (serum) Ca concentrations

  • PTH from the PT gland is released

  • PTH ↑ Ca in the ECF by* ↑ Ca absorption from the intestine (through calbindin)* mobilization of Ca from the bone via stimulation of osteoclasts* ↓ kidney excretion of Ca & ↑ renal tubular reabsorption of Ca


Calcitonin
Calcitonin

  • Calcitonin, is synthesized by the thyroid gland

  • ↑ serum Ca levels stimulates calcitonin

  • Calcitonin ↓ serum Ca concentration by* inhibiting osteoclast activity* prevents mobilization of Ca from bone


Calcitriol 1 25 oh 2 d 3
Calcitriol (1,25-(OH)2D3 )

  • Vit D enters circulation after synthesis inthe skin or consumption in the diet

  • Vit D is transported through the body bound to a vitamin D-binding protein

  • Vit D is taken to the liver, undergoes hydroxylation  forms 25(OH)D

  • 25 (OH)D is bound again to the bindingprotein  kidney where it is furtherhydroxylated  1,25(OH)2D3, the most active vitamin D metabolite


Calcitriol 1 25 oh 2 d 31
Calcitriol (1,25-(OH)2D3 )

  • In Ca deficiency, more 1,25 (OH)2D3 is produced causing enhanced* intestinal absorption of Ca* renal reabsorption of Ca* ↑ bone formation & resorption


Regulation calcium balance intracellulary
Regulation - calcium balance (Intracellulary)

  • Calcium Pumps* ATP dependent calcium pumps found* mitochondria * endoplasmic reticulum * nucleus * these enable movement of Ca from extracellular to intracellular fluid


Interactions with other nutrients
Interactions with other nutrients

  • Phosphorus

  • Magnesium





Interactions with other nutrients4
Interactions with other nutrients

  • Alcohol

  • Sodium & Protein


Deficiency causes
Deficiency - Causes

  • Inadequate intake

  • Poor Ca absorption and/or excessive Ca losses

  • Observed


Hypo hypercalcemia
Hypo - & Hypercalcemia

  • Hypocalcemia

  • Hypercalcemia

  • Fatal levels:


Deficiency observed
Deficiency - observed

  • Disease states

  • Individuals who have ↑ need


Calcium disease prevention
Calcium & disease prevention

  • Osteoporosis

  • 2 types of osteoporosis



Calcium disease prevention2
Calcium & disease prevention

  • Hypertension

  • Cardiovascular Disease

  • Colon Cancer


Calcium disease prevention3
Calcium & disease prevention

  • Other Cancers

  • Kidney Stones

  • Other Disorders


Calcium disease prevention4
Calcium & disease prevention

  • Weight Management


Calcium deficiency
Calcium Deficiency

  • Children - rickets

  • Hypocalcemia


Deficiency
Deficiency

  • Symptoms of tetany

  • Other


Toxicity
Toxicity

  • Tolerable upper intakes 2500 mg/d for all population subcategories

  • Toxicity caused


Assessment sensitive accurate methods
Assessment - sensitive & accurate methods

  • Flame photometry & atomic absorptionspectroscopy

  • Dual-energy X-ray absorptiometry (DEXA)




Recommendations
Recommendations

  • In the US 50% - 75% of adults have ↓ dietaryCa

  • Adults need 1,000 & 1,300 mg/d




What to look for in a supplement
What to look for in a supplement? of milk

  • Check label to see the amount of elemental calcium & how many doses or pills to take

  • The “best” supplement must meet pt/client needs Ask questions:


Other things to consider
Other things to consider of milk

  • Purity:

  • Absorbability:


Other things to consider1
Other things to consider of milk

  • Tolerance:

  • Calcium Interactions:


Dietary supplements
Dietary Supplements of milk

  • Conflicting recommendations as to when to take Ca supplements

  • Experts - no more than 500 mg shd be taken at a time

  • Research shows to spread doses throughout the day, with the last dose near bedtime


May need extra ca
? May need extra Ca of milk

  • Post-menopausal women

  • Amenorrheic women


May need extra ca1
? May need extra Ca of milk

  • Lactose intolerance

  • Pure vegans


Calcium medication interactions
Calcium & medication interactions of milk

  • Calcium supplements ↓ absorption of drugs when taken at the same time* digoxin (heart)* antibiotics (fluroquinolones, tetracycline)* thyroid hormone (levothyroxine)* anticonvulsants (phenytoin)* diuretic (thiazide)* glucocorticoids (prednisone)* aluminum or magnesium containing antacids