Table of Contents
Bone is Alive
Contrary to the common belief that the skeleton is a static "stone" structure, bone is a metabolically active tissue constantly renewing itself. Every 10 years, we completely renew our skeleton. Osteoporosis occurs when the rate of resorption (destruction by osteoclasts) exceeds the rate of formation (construction by osteoblasts).
1. Introduction: The Silent Epidemic
Osteoporosis is often called a "pediatric disease with geriatric consequences." This is because peak bone mass is acquired by age 25-30. After this age, we enter a slow physiological decline. The larger the "bone bank account" built in youth, the lower the risk of fractures in old age.
Currently, osteoporosis affects more than 200 million people globally. Hip (femur) fracture is the most devastating complication, with a mortality rate of up to 20% in the first year following the event.
2. Physiology: The Remodeling Cycle
Bone health depends on a fine balance between two main cells:
- Osteoclasts: Cells that "excavate" old bone, releasing calcium into the bloodstream.
- Osteoblasts: Cells that fill the gaps with new bone matrix, which is subsequently mineralized.
Hormones like estrogen (in women) and testosterone (in men) are natural protectors of osteoblasts. In menopause, the abrupt drop in estrogen accelerates osteoclast activity, leading to rapid bone loss.
3. Calcium: The Structural Brick
Calcium is the most abundant mineral in the body, with 99% stored in bones and teeth. If dietary intake is insufficient, the body "steals" calcium from the bone to maintain vital functions like heart contraction.
| Food Source | Bioavailability | Note |
|---|---|---|
| Dairy (Milk, Yogurt, Cheese) | High | The most concentrated and easily absorbed source. |
| Dark Green Vegetables (Kale, Broccoli) | Medium/High | Kale has excellent absorption, better than spinach (rich in oxalate). |
| Seeds (Sesame, Chia) | Medium | Should be ground or soaked to improve absorption. |
| Sardines (with bones) | High | Also rich in Vitamin D and Omega-3. |
4. Vitamin D: The Essential Transporter
Calcium without vitamin D is chemically useless. Vitamin D (Calcitriol) is responsible for opening the intestinal doors for dietary calcium absorption. Without it, we absorb only 10-15% of ingested calcium.
Vitamin D deficiency is endemic globally. Sun exposure (UVB) is the main source, but the modern lifestyle (offices, sunscreen) often makes supplementation necessary to achieve optimal serum levels (>30 ng/mL for bone health).
5. Beyond Calcium: Protein, K2, and Magnesium
Bone is not made of chalk alone. It has a flexible protein matrix (collagen). Adequate protein intake is vital for bone structure, especially in the elderly.
- Vitamin K2 (MK-7): Activates osteocalcin, a protein that "glues" calcium into the bone matrix, preventing it from depositing in arteries.
- Magnesium: Regulates calcium transport and parathyroid hormone (PTH) secretion.
6. Wolff's Law and Mechanotransduction
Wolff's Law (1892) postulates that bone adapts to the loads it is placed under. Physical exercise generates microscopic deformation in the bone, creating a piezoelectric effect that signals osteoblasts to deposit more bone mass.
Best Exercises (Osteogenic)
- Strength Training: Tendon traction on the bone is the most potent and localized stimulus.
- Impact: Running, jumping rope, dancing, and tennis. Impact against gravity is crucial.
- Not Effective for Density: Swimming and Cycling. Although excellent for the heart, they do not offer enough gravitational impact to stimulate bone formation.
7. The Bone Thieves (Modifiable Risk Factors)
Certain habits accelerate calcium excretion or inhibit osteoblasts:
- Smoking: Directly toxic to osteoblasts and anticipates menopause.
- Excess Alcohol: Interferes with calcium and Vitamin D metabolism.
- Excessive Caffeine: Can slightly increase urinary calcium excretion (compensable with a calcium-rich diet).
- Sedentary Lifestyle: Immobility leads to rapid bone resorption (e.g., astronauts lose bone mass in space due to lack of gravity).
8. Diagnosis and Monitoring
Osteoporosis is silent until the first fracture occurs. Preventive screening is done through Bone Densitometry (DXA).
The exam compares the patient's density with that of a healthy young adult (T-score):
- Normal: T-score up to -1.0.
- Osteopenia (Alert): T-score between -1.0 and -2.5.
- Osteoporosis: T-score below -2.5.
9. Conclusion
Osteoporosis prevention is a lifelong project. It begins in childhood with building a robust bone reserve and continues into adulthood with maintaining that mass through strategic nutrition and mechanical stimulus. Aging need not be synonymous with frailty; with the right interventions, it is possible to maintain a strong and functional skeleton until the end of life.