We can stand upright because our bones form a sturdy internal framework to which our muscles and skin are firmly attached. Without bones, the human body would collapse into a quivering mass of tissue.

Bones are not static. They are living, dynamic tissues that grow in length and width during childhood and adolescence. At birth, we are only about 50cm long and grow to an adult height of over 150cm. In females, bone growth usually stops around 18 years of age, and in males 21 years, when the epiphyseal plates at the ends of long bones close.

Even after growth stops, bones continue to remodel throughout life. Old bone cells constantly break down and are replaced with new ones. Peak bone mass is attained between the ages of 25 and 30. After the age of 40, bone loss begins to exceed bone formation, and bones gradually become weaker. If peak bone mass achieved is inadequate, bones become weak even earlier. Weak bones can lead to fractures, especially of the hip, thigh, ribs and wrist.

Women are more prone to weak bones, especially if they have a small frame or a family history of osteoporosis. In both sexes, inadequate calcium intake during childhood and adolescence can lead to low bone mineral density. Children who are born preterm, are picky eaters, follow fad diets or rely heavily on junk food are particularly at risk.

Certain medical conditions affect bone health. Gastrointestinal surgeries like bariatric surgery reduce the surface area available for nutrient absorption, leading to deficiencies in calcium and other nutrients. Long-term use of steroids, acid reflux medications or anti-epileptic drugs can also impair calcium absorption.

Even if calcium intake is adequate, its absorption and incorporation into bone tissue requires an adequate supply of Vitamin D3, which is obtained from the diet, sunlight exposure or supplements.

Effective calcium incorporation into bones requires microscopic stress. This occurs during weight-bearing exercises such as walking, jogging, running, dancing and weight training. Non-weight-bearing exercises like cycling, swimming and elliptical workouts improve cardiovascular fitness but do not significantly strengthen bones. Excessive alcohol consumption and tobacco use, in any form, reduce bone density and can negate the benefits of good bone health in adults.

The recommended calcium intake varies with age — about 200 mg/day in infants and up to 1,300 mg/day after age 10. Vitamin D requirements increase from 400 IU/day in infants to 600 IU/day in adults. Requirements are higher during pregnancy and lactation.

Children may develop weak bones if they are born prematurely, have inadequate calcium intake, limited sunlight exposure or low physical activity. Many children today spend long hours indoors, glued to television screens or mobile phones. Early signs of deficiency include a large forehead, rib cage deformities, delayed teething, bow legs, frequent fractures and short stature. Some children can develop weak bones due to kidney or gastrointestinal diseases or prolonged steroid therapy.

Weak bones can be diagnosed through blood tests and bone scans. In adults, bone weakness may be due to osteoporosis or osteomalacia. Osteomalacia results from Vitamin D deficiency. The bones become soft, and there is muscle pain, bone tenderness and a waddling duck-like gait. Osteoporosis, in contrast, is painless and asymptomatic, often detected only after a fracture occurs.

To prevent bone weakness:

• Ensure adequate calcium and Vitamin D intake from childhood
• Get regular sunlight exposure
• Exercise aerobically for 30-40 minutes daily
• Include weight-training exercises regularly

Strong bones built early in life are the best investment for healthy, pain-free and fracture-free ageing.

The writer has a family practice at Vellore and is the author of Staying Healthy in Modern India. If you have any questions on health issues, please write to yourhealthgm@yahoo.co.in