Calcium

Question 1

Calcium absorption in our diet

Answer 1

Around 25-30% of calcium consumed is absorbed into the body, the rest is excreted
There are different physiological and dietary factors which can increase absorption in the diet to some extent such as pregnancy and growth
Calcium is reliant on Vitamin D (most of vit D is from sunlight exposure)

Question 2

What is bioavailability?

Answer 2

Bioavailability is the proportion of a nutrient that is absorbed, utilised and made available to the body
Calcium content of foods does not mean that, that is the amount bioavailable

Question 3

Is more calcium better?

Answer 3

Calcium is a threshold nutrient, if you have too low an intake will affect bones however having more than required will not build better bone

Question 4

How is calcium absorbed?

Answer 4

Active transport: regulated by dietary intake and body’s needs, calcium channels and calcium binding protein, can be saturated
Passive diffusion: not saturated, bioavailability. Promotors: proteins/amino acids, lactose, acidic gut Inhibitors: oxalate, other minerals, phytate

Question 5

Calcium excretion

Answer 5

Can’t store calcium although bone is a reservoir, main route is urine, obligatory loss of calcium in urine, factors affecting calcium loss (protein, sodium and caffeine increase, phosphorus, bicarbonate and citrate decrease), some losses in feces and sweat

Question 6

Calcium regulation

Answer 6

In blood: plasma Ca is biologically active, blood concentration tightly controlled
Organ systems that main plasma calcium are kidneys (excretion), intestines (absorption) and bones (reservoir)
Hormones involved: vit D, parathyroid hormone and calcitonin

Question 7

Functions of calcium

Answer 7

Intracellular messenger- nerve transmitter, muscle contraction, hormone secretion, cell membrane function
Bones- structural role (skeleton), physiological role (reservoir of essential minerals)

Question 8

What are the two types of bone found in the teeth?

Answer 8

Cortical bone: compact/dense, slow turnover, 80% of bone mass
Trabecular bone: spongey, day to day withdrawals of blood and hormones, 20% of bone mass

Question 9

How is bone remodelled?

Answer 9

Reshape bone to acccomate changing mechanical loads
Remodelled by osteoblasts, osteoclasts and osteocytes
Reabsorption: removal of old bone
Formation: replacement with new bone

Question 10

What is Peak bone mass?

Answer 10

Maximum amount of bone you can have
Determinants of peak bone mass: genetics and environmental factors such as physical activity, smoking, medications and nutrition

Question 11

What is Osteoporosis?

Answer 11

Occurs when there is more resorption than formation (more bone being broken down than being made), the total amount of bone in the skeleton begins to decline and bones become more fragile