FNH 250 M.12 - Nutrients for Bone Health

what are bones made of?

primarily mineral crystals (strength) and collagen (flexibility)

what are the main functions of bones?

protect organs, allow movement with muscles, store minerals, house blood cell production and maintain posture

are bones living tissue?

yes - they have nerves, blood supply and are constantly broken down and rebuilt

what is bone density?

how tightly minerals are packed into bone, indicating bone strength

name two lifestyle factors that improve BMD

physical activity, adequate nutrient intake

name two factors that can reduce BMD

excess alcohol, high stress

what is bone growth

increase in length and density

what is bone modelling?

shaping of bones during growth

what is bone remodelling?

continuous bone breakdown (osteoclasts) and rebuilding (osteoblasts)

when is peak bone mass reached?

early adulthood

why is peak bone mass important?

higher peak mass reduces osteoporosis risk later

name the six nutrients for bone health

calcium, phosphorus, vitamin D, magnesium, vitamin K, vitamin A

what is fluoride important for?

teeth

what percentage of body calcium is in bones?

99%

What are main functions of calcium in bone?

forms hydroxyapatite crystals for hardness, acts as mineral reserve

functions of calcium in fluids

regulates BP, clotting, muscle contraction, nerve signaling, hormone secretion

effects of calcium deficiency

osteoporosis - bone loss without early symptoms

toxicity risk of calcium

kidney stones from supplements

best sources of calcium

dairy, fortified milk/soy milk, fish with bones, some leafy greens (but spinach has lower bioavailability)

what is the RDA for calcium?

1000 mg/day

which hormones maintain calcium levels

parathyroid hormone (PTH), vitamin D, calcitonin

How does PTH respond to low blood calcium?

activates vitamin D, increases kidney reabsorption, stimulates bone breakdown, increases gut absorption

how does calcitonin respond to high blood calcium?

Reduces kidney reabsorption, inhibits bone breakdown.

Role of phosphorus in bone?

Forms phosphate in hydroxyapatite (85% stored in bone).

Risk of high phosphorus + low calcium?

Bone mineral loss, calcification of soft tissues.

Vitamin A role in bone?

Needed for bone modeling/remodeling; excess stimulates osteoclasts, causing bone breakdown.

Forms of vitamin D?

Ergocalciferol (plants), cholecalciferol (animals).

vitamin D activation steps?

Liver (calcidiol) → kidney (calcitriol – active).

vitamin D main role?

Maintain calcium balance (absorption, reabsorption, release from bone).

vitamin D deficiency effects?

Rickets (children), osteomalacia/osteoporosis (adults).

risk factor for vitamin D deficiency

Dark skin, low sunlight, no fortified milk, elderly, breastfed infants without supplements.

vitamin D toxicity effects

From supplements → hypercalcemia, soft tissue calcification.

vitamin D food sources

Oily fish, fish oil, eggs, fortified milk/margarine.

RDA for vitamin D

15 mcg (600–2000 IU).

Where is magnesium stored?

>50% in bone.

magnesium roles

Part of bone crystal, enzyme cofactor, ATP production, BP regulation, muscle/nerve function.

explain magnesium and calcium’s effects in muscles/blood clotting?

Calcium promotes, magnesium inhibits.

magnesium deficiency symptoms

Rare; can cause nerve issues, weakness, hallucinations.

magnesium toxicity symptoms

A: From supplements – can be fatal.

sources of magnesium

Nuts, legumes, whole grains, dark green veggies.

RDA for magnesium

310–420 mg/day (varies by sex and age).

fluoride main role

Forms fluorapatite in bone/teeth – strengthens, resists decay.

fluoride deficiency effects

weak teeth, dental caries

fluoride excess effects

fluorosis - pitted discoloured emamel

fluoride sources

Fluoridated water, seafood, tea.

fluoride AI

3–4 mg/day.

vitamin K’s role in bone

Helps osteocalcin bind calcium for mineralization.

vitamin K deficiency effect on bone?

Unclear; deficiency mainly causes poor blood clotting.

vitamin K sources

Green vegetables, vegetable oils, gut bacteria.

AI for vitamin K

90 mcg (women), 120 mcg (men).