Nutrition and the skeleton

Question 1

How much of the bone is protein %?

Answer 1

50%

Question 2

What happens in bone turnover and what is the duration?

Answer 2

• with synthesis and degradation taking place on continual basis
• much slower, months?
• related to activities of cells (osteoblasts = forming, osteoclasts = breaking down)
• bone resorption and formation process

Question 3

What are the general factors influencing bone formation and resorption?

Answer 3

nutritional and hormonal factors

Question 4

What specifically are nutritional factors affecting formation and resorption?

Answer 4

• nutritional status, energy and protein
• calcium and phosphate requirement
• vit D
• zinc
• vit C
• iodine (thyroid activity)
• micronutrients

Question 5

What is the effect of vit D on bone?

Answer 5

• direct effects on bone cells

- on calcium absorption

Question 6

What is the effect of zinc on bone?

Answer 6

• alkaline phosphatase activity

- indirectly via sex steroid and growth factor activity

Question 7

What is vit C required for in bones?

Answer 7

collagen hydroxylation

Question 8

What specifically are hormonal factors affecting formation and resorption?

Answer 8

• thyroid hormone in skeletal maturation
• direct/indirect effects
• indirect = via IGF-1
• PTH produced in response to low blood calcium

Question 9

What happens as PTH produced responds to low blood calcium?

Answer 9

• increases bone mass degradation and loss calcium to increase blood calcium
• increase vit D activity (via upregulating hydroxylase enzyme activity in kidney)
• leads to increase calcium absorption in GIT

Question 10

What hormones rise during puberty?

Answer 10

• systemic GH/IGF-1
• estrogen, due to sex hormone increase and aromatisation of testosterone in males
• estrogen incerases GH release too

Question 11

What are factors can influence bone mass?

Answer 11

• genetics
• gender
• hormones
• nutrition
• physical activity

Question 12

What age is peak bone mass usually at?

Answer 12

20-30yo

Question 13

What diets need to be carefully monitors or avoided during growth and development?

Answer 13

• vegan/vegetarian diet

- energy restricted diet

Question 14

How do vegan/vegetarian diets pose problems in growth and development?

Answer 14

• low/no red meat, important associated nutrients there (amino acids, zinc, phosphorus)
• low/no dairy (low calcium, vit D and iodine)
• high phytake intake (reduce calcium absorption)