Osteoporosis

What Is Osteoporosis?

Osteoporosis is a skeletal disease characterized by decreased bone mineral density (BMD) and deterioration of bone microarchitecture, leading to increased bone fragility and susceptibility to fractures. Bone is a dynamic tissue that is continuously remodeled through cycles of resorption by osteoclasts and formation by osteoblasts. Osteoporosis develops when bone resorption exceeds bone formation over time, resulting in a net loss of bone mass.

Diagnosis is made via dual-energy X-ray absorptiometry (DEXA) scan; a T-score at or below -2.5 standard deviations from the young adult mean defines osteoporosis, while scores between -1.0 and -2.5 define osteopenia. Approximately 200 million people worldwide have osteoporosis, and it is responsible for over 8.9 million fractures annually. Hip fractures, the most serious consequence, carry a one-year mortality rate of 20–30% in older adults.

Risk Factors and Bone Physiology

Peak bone mass is achieved between ages 25 and 30 and is determined roughly 60–80% by genetic factors, with the remainder influenced by nutrition and physical activity during childhood and adolescence. After peak bone mass, gradual loss begins; in women, the rate accelerates sharply after menopause due to estrogen withdrawal, with losses of 1–3% per year in the first 5–10 years post-menopause.

• Non-modifiable risk factors: female sex, advanced age, white or Asian ethnicity, family history, small body frame
• Modifiable risk factors: calcium and vitamin D deficiency, physical inactivity (especially lack of weight-bearing exercise), smoking, excessive alcohol, long-term glucocorticoid use, low body weight
• Secondary causes: celiac disease, inflammatory bowel disease, hyperparathyroidism, and eating disorders can each accelerate bone loss

Nutritional Strategies for Bone Health

Calcium and vitamin D are the foundational nutrients for bone health, but they do not act in isolation. Adequate calcium intake (1,000 mg per day for adults aged 19–50; 1,200 mg per day for women over 50 and men over 70) is best achieved through food: one cup of milk or fortified plant milk provides approximately 300 mg, and one cup of cooked kale or bok choy provides 90–180 mg of highly bioavailable calcium. Vitamin D (600–800 IU per day; many experts recommend 1,000–2,000 IU for those at risk of deficiency) is essential for intestinal calcium absorption; without adequate vitamin D, only 10–15% of dietary calcium is absorbed compared to 30–40% when vitamin D status is replete. Vitamin K2 (as MK-7) activates osteocalcin, a protein that incorporates calcium into bone matrix; fermented foods, particularly natto, are the richest dietary sources. Adequate protein intake (0.8–1.2 g per kg per day) supports bone matrix synthesis without accelerating calcium excretion as was once feared. Excessive sodium (above 2,300 mg per day) increases urinary calcium losses by approximately 40 mg per 2,300 mg of sodium consumed. Phosphoric acid in carbonated soft drinks may displace calcium-containing beverages in the diet, contributing to lower bone density when consumption is habitual.