Formation and Maintenance of Healthy Bones

In order to understand how you can improve bone health, it helps to fist understand how bones are formed, what makes bones weak and how the body maintains the bone structure. Many people think that bones grow in childhood and apart from healing when fractures occur, very little happens with the bones once they are formed. In reality, just as with other tissues in the bone, bone is alive and active and is constantly maintained; bone cells break down and new bone cells form throughout life.

What Exactly is Bone?

The structure of bone comprises four main elements. The middle of most bones is hollow which helps to keep the weight down, improves flex and adds to bone strength. Inside this cavity you will find bone marrow; a highly fatty substance which has an important role in the production of red blood cells. Moving outwards you will come to a layer of spongy bone called cancellous bone which makes bones more flexible. Next is cortical bone, which is the hard outer layer that most people associated with bone. Finally there is the thin bone lining called the periosteum, which contains a rich network of nerves and blood vessels to supply nutrients and minerals to maintain bone health.

Bone is made from two main elements: Minerals such as calcium, phosphorus and magnesium and from connective tissue called collagen. Minerals are the structural elements which ensure the bones are strong, while collagen is vital to give the bones some flexibility. It is vital that bones are not entirely rigid as being able to flex to a small degree can help to dissipate shocks and will prevent them snapping when stress is applied.

Bone is far more complex than many people would think, and it is not just a static skeletal element on which the muscles are hung and to keep the body in the proper shape. Bone acts as a store for important minerals such as magnesium, phosphorus and calcium. When the levels of these vital minerals are low, the body is able to break down bone to make sufficient levels available for metabolic purposes. Calcium for example may be the major component of bone, but it also has many other important roles throughout the body. Sufficient levels must be made available to ensure that the muscles are able to contract properly, that nerves can function, and that the cells in your body can communicate with each other. If bone was unable to release calcium, should a deficiency arise it would have deadly consequences.

Breakdown of Old Bone and Formation of New Bone

The breakdown of old bone and the formation of new bone cells is vital, not only to ensure that stress fractures and breaks can heal, but also to ensure that calcium can be regulated within the body. The process of bone maintenance is called bone remodeling, and the extent to which this occurs may be surprising. During the first year of life an infant will have the entire skeleton replaced, and in adults approximately a tenth of the skeleton is broken down and replaced over the course of a year. In other words, every 10 years you will have an entirely new skeleton. As you can see, bone is far from a static structural element.

There are two main cellular structures which are responsible for breaking down old bone (termed bone reabsorption) and forming new bone (termed ossification), and these are called osteoclasts and osteoblasts respectively. Osteoblasts are formed in the bone lining (the periosteum) and in the bone marrow, and their production is controlled by a number of growth factors. Osteoclasts break down old bone and are produced by the immune system and are regulated by a swathe of hormones in the body, and even osteoblasts release hormones which regulate osteoclast activity. These two types of cell communicate with each other to ensure that the perfect balance between breakdown of bone and formation of new bone is maintained.

Many vitamins and minerals can affect the level of both of osteoblasts and osteoclasts, and in turn they will affect the rate of bone turnover. Unsurprisingly much research has been performed on these elements that control bone turnover to help prevent osteoporosis, osteoarthritis and other bone and joint problems.

What Happens to Bones as we Age?

When the elderly fall down they are much more likely to suffer stress fractures and full bone breaks than children and younger adults. Why do the bones get weak with age?

The main growth phase of bone continues until around the age of 18, but once adults reach their thirties bone starts to be lost. The level of bone loss each year may be small, but by the time you reach your seventies those small yearly losses become highly significant and it is this loss of bone which causes first osteopenia, and then osteoporosis. What’s more, the rate of bone breakdown increases steadily with age. You can expect half to two percent of your bone mass to start to be lost from your early thirties onwards.

Important minerals start to be lost as we age and bones become much thinner. Bones will therefore become more brittle, moisture will also be lost, fluid in the joints will decrease and mineral deposits occur in the joints can form leading to stiffness and a lack of flexibility. With the hormonal changes occurring in the female menopause, the rate of bone loss speeds up considerably and post-menopausal women are far more likely to have brittle bones than men of the same age.

Bone weakening diseases speed up the process of bone loss. Weakened bones are referred to as a condition called osteopenia which is a precursor to osteoporosis; a highly serious disease which often goes unnoticed until the bones become highly brittle and break. Osteopenia is believed to affect over half the population of over 50’s in the United States. Taking steps to improve bone health and prevent osteoporosis and osteopenia is important to ensure good bone health in later life.

How to Maintain Healthy and Strong Bones

It is not possible to stop your bones becoming more brittle and thinning as you age, but it is possible to slow down the process of bone loss to prevent osteoporosis. The first step is to ensure your children develop strong and healthy bones din the first place during the main phase of bone growth. Nutrition plays a vital role in the development and maintenance of healthy bones. Ensuring that the diet contains sufficient levels of minerals important for bone health such as calcium, magnesium, selenium and phosphorus is vital. Vitamins and bone health also go hand in hand, and ensuring proper vitamin intake is also of major importance. Vitamin D, vitamin K, and vitamins A, C and B12 and this can help to prevent osteoporosis and deficiencies can cause serious weakening of the bones.

Maintaining strong and healthy bones is not all about diet, and ensuring you stay physically active can have a profound impact on the health of your bones. Get out and get active and you will suffer far less bone problems than if you lead a more sedentary lifestyle, and getting out in sunlight will also ensure you can synthesize enough vitamin D. Exercise helps to strengthen the bones, and sports improve coordination and balance which can help to prevent falls.

Medical Information and References

NIH Osteoporosis and Related Bone Diseases NRC
American Bone Health