Calcium (Ca++)

and intro to minerals

• Major minerals
• dietary need ≥ 100 mg/day
• Ca, P, Mg etc.

• Trace minerals
• dietary need <100 mg/day
• Iron, copper, selenium, zinc etc.

• Ultratrace elements
• Ug (microgram)
• Vanadium, tin, arsenic, nickel, silicon etc.
The Minerals in Your Body
Calcium
 Calcium
• Divalent cation
• Most abundant mineral in the body
• 40% of total mineral mass
• 1.5% of total body mass
• 99% of calcium is in the bones and teeth
• 1% within intracellular and extracellular fluids
 Digestion and Absorption
Digestion
• Present in foods and supplements as insoluble
salts
• Must be ionized (Ca2+) for absorption; achieved
by acidic stomach pH
• Once ionized, may form complex with other
minerals (reform)
Absorption
• In general, 20-50%, avg. 30% in adults
• Increased up to 60% in pregnancy and with low
calcium intake
• Increased up to 75% in infants, children
Digestion and Absorption
Two main transport processes
Active Transport – Small intestine
• Mainly in duodenum and proximal jejunum
• Saturable – limit to its absorption (and will be excreted
out)
• Requires energy and a transport protein
• Regulated by vitamin D
• Stimulated by low-calcium diets (<400 mg/meal or 1000
mg/d))
Digestion and Absorption
Passive Diffusion
– Small Intestine
• Mainly in jejunum and ileum
• Non-saturable
• Requires neither energy nor transport protein
– Large Intestine (colon)
• Minor route calcium absorption (4-10% of
total)
• Colonic bacteria may release calcium bound
to fermentable fibers, making it available for
absorption
Digestion and Absorption
Dietary factors influencing absorption
Enhancing factors
• Vitamin D (calcitriol) – increased CBP
• Sugars and sugar alcohols – increased solubility
• Lactose– increased solubility
• Protein – uncertain
Inhibiting factors
• Phytate (grains, legumes, nuts) – binds calcium
• Oxalate (vegetables, fruit, nuts) – binds calcium
• Unabsorbed fatty acids – binds calcium
• Caffeine: Increases secretion of Ca++ back into the gut
• Divalent cations (Mg+2, Zn+2) – compete for absorption
 Blocks Absorption
Phytates
Foods mg phytate/100g
Wheat 0.85
Maize 1.02
Barley 0.97
Oats 1.01
Soybean 1.43
Peas 1.02

Inositol hexaphosphate (IP 6)

 Oxalates
Foods mg oxalate/100g

Rhubarb 600-1235
Spinach 600-970
Soy burger patty 870
Beetroot 500
Almond 383
Tofu 140-280
Pecans 202
Peanuts 187
Okra 146
Chocolate 117
Collard greens 74
Sweet Potato 56
 Transport and Storage

• Transport Protein-bound

• 50% free (ionized) Complexed to

anions
• 40% bound to proteins, like Ionized

albumin and pre-albumin

• 10% complexed to anions, like
sulfate, phosphate, and citrate
• Storage
• “Functional stores” in bones and
teeth
 Functions of Calcium
Structural:
ü Teeth and bones
Functional roles in:
- Regulation of muscle contraction
- Nerve impulse transmission
- Regulation of biochemical reactions via calmodulin (2nd
messenger)
- Maintenance of acid-base balance (pH)
- Blood coagulation

Numerous regulatory functions of calcium are performed

by <0.5% of the total body calcium.
Functions

Structural integrity of bones and

teeth
• Calcium phosphate
• Hydroxyapatite crystals
[Ca10(PO4)6(OH)2]
 http://ib.bioninja.com.au/higher-
level/topic-11-animal-physiology/112-
- Role of Calcium in Muscle Contraction movement/muscle-contraction.html
Calcium Channels and Pumps in Muscle Cells

-
 Role of Calcium in Synaptic Junctions and Neurotransmission
-
Calcium as a Second Messenger with Calmodulin Protein to
Activate
-
Enzymes
 Blood Calcium Levels
• Calcium is bound to protein in the blood.
• Blood calcium is tightly regulated by several
endocrine factors.
• Blood calcium levels are closely influenced by:
- Parathyroid hormone
- Vitamin D
- Calcitonin
Regulation of calcium in the blood
 Vitamin D Functions &
Mechanisms of Action (from vit D slide)
Excretion
Urinary
• More than 90% of calcium reabsorbed by kidneys
• Daily calcium losses in urine average 170 mg
Fecal
• From 50-80% of dietary calcium excreted in feces
• Daily endogenous calcium losses in feces average
75 mg
• Factors that increase fecal calcium excretion are
same as those inhibiting absorption
Recommended Intakes
• RDAs
• Females
• 11-18 years: 1300 mg
• l9-50 years: 1000 mg
• >50 years: 1200 mg

• Males
• 11-18 years: 1300 mg
• 19-70 years: 1000 mg
• >70 years : 1200mg
Dietary Sources
Food Serving Calcium
Milk 1c 300 mg
Cheddar Cheese 1.5 oz 300 mg
Tofu, Calcium Set ½c 258 mg
Chinese Cabbage ½ c, cooked 239 mg
White Beans ½ c, cooked 113 mg
Spinach ½ c, cooked 115 mg
Broccoli ½ c, cooked 35 mg
 Assessment

• No routine biochemical method is available to

directly assess calcium status.
• Common to assess bone mineral density
• Dual-energy X-ray absorptiometry (DEXA)
• CT scan (less precise)
 Deficiency

Individuals at risk
• Most commonly related to poor intake and/or high calcium losses

Symptoms
• In children, stunted growth
• In older adults, osteoporosis
• The leading causes of osteoporosis:
• Drop in estrogen in women at the time of menopause
• Drop in testosterone in men.
• Women over age 50 and men over age 70 have a higher risk for osteoporosis.
Toxicity
Individuals at risk
• Individuals consuming high amounts of calcium from diet,
supplements, antacids

Intakes above UL of 2500 mg (for adults 19-50 years)

and 2000 mg (for adults >50 years)
• Constipation
• Kidney stones
• Milk Alkali Syndrome
 Osteoporosis
What?
• Thinning of bone tissue and loss of
bone mineral density (BMD) over time.
Most common type of bone disease.
• Research estimates that:
• Approx. 1 out of 5 American women
>50 yrs has osteoporosis.
• About half of all women > 50 yrs. will
have a fracture of the hip, wrist, or Less dense, weakened,
vertebra and brittle bones

When does it occur?

• Bone resorption is greater than bone
formation
↑ risk of osteoporosis
and bone fractures
Osteoporosis
• Causes
• Vitamin D deficiency
• Hyperparathyroidism
• Chronic rheumatoid arthritis, chronic kidney disease,
eating disorders
• Taking corticosteroid medications (prednisone,
methylprednisolone) every day for more than 3 months,
or taking certain anti-seizure drugs
• Being confined to a bed
 Osteoporosis
• Diet
• Calcium: at least 1,200 milligrams per day of calcium
• 800 - 1,000 IUs of vitamin D3
• Adequate protein

• Exercise
• Weight-bearing -- walking, jogging, playing tennis, dancing
• Resistance -- free weights, weight machines, stretch bands
• Balance exercises -- tai chi, yoga
Avoid any exercise that presents a risk of falling, or high-impact
exercises that may cause fractures.
Milk-Alkali Syndrome
Acquired condition

Caused by
• Increased consumption of milk
• Taking certain antacids, especially calcium carbonate or sodium
bicarbonate (baking soda), over a long period of time

Results in
• High levels of calcium (hypercalcemia)
• Accompanied by a shift in the body's acid/base balance towards
alkalinity.

• If untreated, may lead to calcification and renal failure