ADA in Calcium

8/12/2019 ADA in Calcium

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Introduction

Ca is the most abundant mineral in the body

Ca (latin calx means limestone) was known asearly as the first century when the AncientRomans prepared lime as calcium oxide


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Distribution & function in the body - bone

Over 99% Ca exists in the skeleton

Structural role

Functional role

Ca

status can be assessed by measuring BMC bybone densitometry


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Bone remodeling occurs throughout life

Bone formation is > than resorption duringgrowth (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)


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

2 types of bones* cortical* trabecular

Cortical bone


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Trabecular bone


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Functions

Mineralization - bone & teeth

Blood clotting


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Functions

Other functions


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Solubility

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

Ca in food & dietary supplements - insoluble salts

Solubility - mildly acidic pH

Solubility doesnt ensure better absorption

In alkaline pH, Ca may complex with minerals orother dietary components


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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 betbone & ECF


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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 amountof ionized Ca rather than the total calcium


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Corrected Ca level

Corrected Ca level is used when albumin isabnormal

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


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Absorption

Physiological factors


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Absorption

Occurs along the length of the small intestine

Generally 2 routes of absorption

Other route of absorption


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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 enterocyteas unbound Ca+2

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

Ca+2 leaves the enterocyte in exchange for Na or

by calcium activated ATPase


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Saturable system (Transcellular)

Saturable process occurs


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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 dietaryCa

Ca enters into the enterocyte with the help ofvit D


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Colon

Bacteria in the colon releases Ca boundfermentable 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


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Factors that enhance Ca absorption

lactose

vit D

acidic environment stress

Distribution of Ca intake

physiological need


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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)


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Absorption - enhanced Vitamin D

Acidic conditions

Lack of stress


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Absorption - enhanced Distribution of Ca intake

Increased physiological need


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Factors that inhibit Ca absorption Non-fermentable fibers

Phytate

Oxalate

Magnesium

Dietary fatty acids

Physical activity

Potassium


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Factors that inhibit Ca absorption Non-fermentable fibers

Phytate

Oxalates


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Factors that inhibit Ca absorption

Magnesium

Dietary fatty acids


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Factors that inhibit Ca absorption

PA

Potassium


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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)


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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


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Excretion

Primarily in the urine and feces

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

Urinary Ca excretion is

Urinary Ca excretion is


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Excretion

Most Ca is filtered and reabsorbed by thekidneys


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Excretion

Fecal losses range from 45-100 mg/d

fecal losses are with

Skin losses 60 mg/d


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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


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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


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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 binding

protein kidney where it is furtherhydroxylated 1,25(OH)2D3, the most activevitamin D metabolite


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Calcitriol (1,25-(OH)2D3 )

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


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Regulation - calcium balance

(Intracellulary) Calcium Pumps

* ATP dependent calcium pumps found

* mitochondria* endoplasmic reticulum* nucleus

* these enable movement of Ca from extracellular tointracellular fluid


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Interactions with other nutrients

Phosphorus

Magnesium


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Potassium

Protein


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Sodium

Fiber


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Caffeine


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Alcohol

Sodium & Protein


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Deficiency - Causes

Inadequate intake

Poor Ca absorption and/or excessive Ca losses

Observed


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Hypo - & Hypercalcemia

Hypocalcemia

Hypercalcemia

Fatal levels:


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Deficiency - observed

Disease states

Individuals who have need


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Calcium & disease prevention

Osteoporosis

2 types of osteoporosis


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Type I

Type II


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Hypertension

Cardiovascular Disease

Colon Cancer


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Other Cancers

Kidney Stones

Other Disorders


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Calcium Deficiency

Children - rickets

Hypocalcemia


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Deficiency

Symptoms of tetany

Other


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Toxicity

Tolerable upper intakes 2500 mg/d for allpopulation subcategories

Toxicity caused


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Assessment - sensitive & accurate methods

Flame photometry & atomic absorptionspectroscopy

Dual-energy X-ray absorptiometry (DEXA)


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BMD score


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Treatment - approved FDA

Calcitonin

ET


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Recommendations

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

Adults need 1,000 & 1,300 mg/d


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Ways to increase calcium intake

F d th t id th t f


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Foods that provide the same amount of

calcium as in one cup of milk


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What to look for in a supplement? 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:


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Other things to consider Purity:

Absorbability:


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Other things to consider Tolerance:

Calcium Interactions:


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Dietary Supplements Conflicting recommendations as to when to take

Ca supplements

Experts - no more than 500 mg shd be taken at atime

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


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? May need extra Ca Post-menopausal women

Amenorrheic women


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? May need extra Ca Lactose intolerance Pure vegans


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Calcium & medication interactions 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 containingantacids

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ADA in Calcium