Vitamins /Minerals Involved in Bone Health

Calcium’s Role in Bone Health: Building Block

Over 99% of the body's calcium is in bones and teeth, forming hydroxyapatite, the mineral that makes bones hard.

Calcium’s Role in Bone Health: Remodeling

Bones are dynamic, with old bone being reabsorbed and new bone formed; calcium is needed for this continuous renewal.

Calcium’s Role in Bone Health: Storage

The skeleton acts as a calcium reservoir, supplying calcium to the blood for vital functions like nerve signals and muscle contraction if dietary intake is low, weakening bones. 

Hydroxyapatite

Mineral that makes bones hard,

Peak Bone Mass (PBM): Definition

PBM is the maximum amount of bone density and strength an individual achieves, usually by their late teens to early 30s.

Peak Bone Mass (PBM): Importance

Higher PBM leads to a lower risk of fractures and osteoporosis later in life.

Peak Bone Mass (PBM): Achieving PBM

Achieving PBM: Adequate calcium, Vitamin D (for absorption), and weight-bearing exercise during childhood, adolescence, and young adulthood are critical for maximizing PBM.

Vitamin D (Prohormone): Origin

Synthesized in the skin from sunlight or obtained from diet; converted by the liver and kidneys into its active form, calcitriol (1,25(OH)2D).

Vitamin D (Prohormone): Mechanism

Calcitriol binds to Vitamin D Receptors (VDR) found in many cells, acting like a key to turn on genes that regulate calcium. 

Vitamin D’s Impact on Blood Calcium: Intestines

Increases the absorption of dietary calcium and phosphate into the bloodstream.

Vitamin D’s Impact on Blood Calcium: Bones

Stimulates osteoclasts (bone-resorbing cells) to break down bone, releasing calcium and phosphate when blood levels are low.

Vitamin D’s Impact on Blood Calcium: Kidneys

Works with PTH to signal the kidneys to reabsorb calcium from urine back into the blood, preventing its loss. 

The Calcium-PTH-Vitamin D Connection

• These three work as a feedback loop to keep blood calcium stable.

The Calcium-PTH-Vitamin D Connection: High Calcium

• High calcium reduces PTH, slowing down these processes. 

The Calcium-PTH-Vitamin D Connection: Low Calcium

• Low calcium triggers PTH release, which tells the kidneys to activate Vitamin D, leading to more intestinal calcium absorption and bone mobilization, raising calcium levels.

Calcium Deficiency (Hypocalcemia): Children

Rickets: The hallmark condition, caused by poor mineralization of new bone and cartilage.

• Symptoms: Bowed legs, widened wrists/ankles, stunted growth, delayed walking, frontal bossing (bulging forehead), rachitic rosary (beads on ribs).

Calcium Deficiency (Hypocalcemia): Infants

• Infants: May present with irritability, poor feeding, jitteriness, seizures

Calcium Deficiency (Hypocalcemia) in Adults: Osteomalacia

• Osteomalacia: Softening of adult bones, leading to pain and weakness.

  • Symptoms: Chronic muscle aches and pains, bone pain (especially in hips, lower back, legs), increased fracture risk, fatigue, weakness.

Calcium Deficiency (Hypocalcemia) in Adults: Osteoporosis

• Osteoporosis (Long-Term): Increased risk of brittle bones and fractures.

Calcium Deficiency (Hypocalcemia) in Adults

• Calcium Deficiency (Hypocalcemia): Tingling/numbness (paresthesia), muscle cramps, spasms, irregular heartbeat, dry skin/nails, anxiety, seizures in severe cases. 

Key Differences in Calcium Deficiencies in Adults vs Children

• Children: Focus on bone formation issues (rickets) due to rapid growth.

• Adults: Focus on bone density loss and softening (osteomalacia/osteoporosis) and general muscle/nerve function. 

Vitamin D: Function

Acts as a steroid hormone (calcitriol) that significantly increases the gut's ability to absorb dietary calcium and phosphorus.

Vitamin D: Synthesis to Active Form

1. Skin/Diet: Sunlight converts a precursor in the skin, or it's obtained from food/supplements.

2. Liver: The liver converts it to 25-hydroxyvitamin D (calcidiol).

3. Kidneys: The kidneys further convert it to the active hormone, 1,25-dihydroxyvitamin D (calcitriol).