Your skeleton is constantly rebuilding itself, but the balance can shift.

Space · Published 8 October 2026 Swipe more like this →

In short: Your entire skeleton is replaced roughly every 10 years through a continuous cycle of destruction and creation. However, when the body reabsorbs old bone faster than it can manufacture new tissue, the structural integrity of your frame begins to fail, potentially leading to fragile, brittle bones.

Bone health relies on a delicate metabolic coupling between bone formation and resorption. In a healthy body, these cellular events remain in balance, ensuring the skeleton remains strong. However, bone loss occurs when the cellular events of resorption are quantitatively larger than those of formation. This imbalance can happen as a normal part of aging, but it can also be accelerated by various factors. This metabolic process is highly active throughout life. Bone is a tissue that undergoes constant remodelling to maintain its structural integrity.

For many, the first sign of significant bone loss is a fracture caused by everyday activities or minor accidents. This stage of fragility is known as osteoporosis. Before reaching this stage, individuals may experience osteopenia, a condition where bone density is lower than average for one's age but has not yet reached the threshold for an osteoporosis diagnosis. While osteopenia does not always progress to osteoporosis, it serves as a critical window for intervention. In some cases, a person might suffer a broken bone before realising they have lost density. This can sometimes be triggered by something as simple as a sneeze or a cough.

Several biological and lifestyle factors influence this equilibrium. For women, a drop in estrogen during menopause is a major driver of bone loss, while men may experience similar issues due to declining testosterone as they age. Beyond hormones, physical inactivity, smoking, alcohol consumption, and deficiencies in calcium or vitamin D can all increase the risk of bone fragility. Even extreme environments, such as spaceflight, are studied to understand how changes in bone density occur, even during short-duration missions. Dietary habits also play a role, as failing to consume enough high-calcium foods can impact bone strength. Additionally, the body may struggle to absorb sufficient calcium from your diet.

General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.

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