calcium 4.2

What is calcium

• divalent cation

• most abundant mineral in the body 40%

where is calcium in the body?

• 99% bones and teeth

• 1% blood, ECF and soft tissues (muscle)

excellent sources of calcium

• dairy items

• fortified plant based milks

• fortified OJ and cereal

good sources of calcium

• tofu

• collard greens

• canned salmon

poor sources of calcium

• meats

• grains

Calcium supplements

• found in what form?

• with vitamins?

• most common forms of calcium in supplements?

• forms of supplements

• multivitamin/ mineral supplements

• alone or with Vitamin D

• calcium carbonate and calcium citrate

• pill forms are large, gummies, tablets, chewable, liquid

Who is calcium citrate good for? need food?

• better for those with low gastric absorption

• older adults

• does not need food for absorption

Why calcium carbonate? need food?

• inexpensive

• found in antacids

• absorbed better with food

what is hypercalcemia?

• higher than normal blood levels of calcium as a result of too much supplementation not from diet

signs and symptoms of hypercalcemia

• kidney stones

• fatigue

• bone pain

• muscle weakness

• nausea

• vomiting

• arrhythmia

Describe calcium digestion, absorption, and transport

1. calcium crossing brush boarder through TPPV6

2. calcium binds calbindin within the cell - SI

3. Ca2+ ATPase or Na+/Ca2+ exchange pump Ca2+ cross basolateral membrane to enter the blood

4. Ca2+ absorbed between cells (only with high calcium concentrations)

Calcium can be solubilized to exist as _______ ______ from most calcium salts in about 1 hour at an acidic pH (as occurs in the stomach).

Ca2+

Factors that influence calcium absorption

• life stage and diet

• infants, children, and women during pregnancy and lactation have great calcium absorption

What enhances calcium absorption

• calcitriol

• stomach acid

• lactose, other sugars, sugar alcohols

• protein

what inhibits calcium absorption

• vit d deficiency

• low stomach acid

• high fiber diet

• phytic oxalic acid intake - lots of fruits and veg

• fat malabsorption conditions

Oxalic acid and calcium absorption

• can reduce absorption to <5% when in GI tract with calcium

• promotes calcium excretion

• found in fruits(berries), veg(spinach, beets), nuts (peanuts)

• plants should not be avoided eat a variety

Calcium and bone mineralization

• teeth

• bone mineral composition

• outer enamel largely made up of calcium w/ phosphorus and magnesium

• 50-70% of bone weight comes from minerals (web of water, lipids, minerals)

What is bone mineralization

the process when minerals incorporate into hardened crystalline structure known as hydroxyapatite

2 Cell types responsible for bone turnover are

osteoclast and osteoblast

What are osteoblasts

cells that forms matrix; which becomes calcified over time

• blast, bone

what are osteoclasts

release minerals; reabsorb previously made bone

what are the 3 hormones involved in the tightly regulated pathway that is necessary to ensure blood and extracellular levels are maintained?

PTH, calcitonin, calcitriol

Where is PTH secreted from

parathyroid gland when calcium falls

where is calcitriol secreted from

kidney when blood calcium levels fall (stimulated by PTH)

Where is calcitonin secreted from

thyroid gland when blood calcium levels rise

the three hormones do what to achieve an ideal blood calcium level which has a range of 8.5-10.5

they either work together or have opposing functions

when calcium in the blood falls what happens

• PTH secreted from the parathyroid glands

• PTH stimulates Vit D, increases osteoclast activity(bone breakdown), increases calcium retention in the kidneys, increases absorption in S.I.

• Blood calcium rises and PTH secretion is inhibited

when calcium in the blood rises what happens

• calcitonin is secreted from the thyroid gland

• calcitonin inhibits vit D, increases osteoblast activity (bone formation), decreases calcium retention in kindeys, decreases calcium absorption in S.I

• Blood calcium falls and calcitonin secretion is inhibited

What does calcium deficiency co present with in infants and children

rickets

What does calcium deficiency lead to in adults

osteoporosis which increases risk of disease development

non modifiable risk factors for osteoporosis

family hx, white/asian ancestry, female, age/older adults, small, thin body frame

modifiable risk factors for osteoporosis

physical activity, smoking, excessive alcohol, not eating calcium/ vitamin d foods; certain meds, low estrogen/testosterone levels, disordered eating

What are the major sites of osteoporosis related fractures

hip, vertebrae, wrist, ankle

when does peak bone mass occur

20 years old

paracellular absorption of calcium occurs by

diffusion mainly in the jejunum and ileum

what substance can improve calcium absorption

lactose

calcium and what mineral are major part of crystal hydroxyapatite, formed in ossification of bone

phosphorus

meats and grains are poor sources of calcium

true

calcium can be absorbed via

passive diffusion in the small intestine

which cells are considered the bone building cells

osteoblasts