Bone Density

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Bone Density

A measurement of the amount of calcium and other minerals in a segment of bone, a higher mineral content indicating a higher bone density and strength, used to detect osteoporosis or monitor its treatment. [1]

We tend to think of bones as these things we were born with – they’re just ‘there’. But bones are actually a lot more complex than most of us would think.

Bone Structure

Despite the skeleton’s incredible ability to support a human being, and protect all the internal organs of the body, bones are not solid masses. In fact, despite their profound strength, they are actually pretty lightweight. Bones contain osteocytes (living cells), nerves, and blood vessels, which are protected by a strong layer made up of calcium and phosphorous. Finally, the entire structure is covered by a membrane called the periosteum.

There are two types of bone – spongy or compact. Spongy bone is a very light material, made up of lots of small pieces of bone with spaces in between, rather like mesh. Small bones within the body, such as in the wrist and ankle, are made up of spongy bone. Compact bone, on the other hand, is dense and heavier and makes up the long bones, such as those in the limbs. In addition, every bone in the body is covered in a layer of compact bone.[2]

How Do Bones ‘Work’?

Did you know that the entire human skeleton is replaced approximately every seven years? Bones are living things, and are in a constant cycle of regeneration. Bone forms, gets resorbed, and new bone takes its place.[3] We’re born with around 300 bones, but as we grow some of those bones fuse together, and some cartilage is replaced with bone tissue, so by the time we reach adulthood we only have 206 bones.

Peak Bone Density

The childhood and teenage years are when most bone mass is achieved. As we head into adulthood bones become denser, bigger, and heavier. Peak bone density, when the bones are at their strongest and most dense, is reached somewhere around the age of 30.

After this age, the status quo changes, and the rate at which bone mass is lost is greater than the rate at which it is replaced.

Although both men and women attain peak bone density at around the same age, the rate at which it is lost occurs more rapidly in women. In the first few years of the menopause, women’s bone density can take a massive hit and this loss continues into old age. Men, on the other hand, tend not to experience this decline in bone health until much later – 70 or older. The reason for the earlier decline in women is the drop in oestrogen levels during menopause, as oestrogen is the hormone which is responsible for bone health. In the years following the menopause, this loss of bone mass can slow, but then speed up again in line with that of men, at the age of around 70.[4]

Diseases Which Affect Bone Density

Besides the inevitable occurrence of menopause and old age, there are several other conditions which can contribute to the loss of bone density.

Diabetes

It is thought that high blood sugar may cause bone formation to slow down so that those who suffer from Diabetes regenerate less bone tissue than those without. As Type 1 commonly begins in childhood, which is when our bone growth most rapidly occurs, this can greatly contribute to the development of osteoporosis (the medical name for loss of bone mass) later in life.

Inflammatory Disease

Any disease which causes high inflammation can result in osteoporosis. Conditions such as Lupus, or Rheumatoid Arthritis, cause the body’s immune system to attack itself, resulting in chronic inflammation. This inflammation can then cause the cycle of loss and repair to become more rapid, causing an increased turnover of bone growth. Furthermore, in most auto-immune conditions, long-term steroid use is prescribed, and it is thought that steroids can hinder bone building activity.

Hyperthyroidism

When the body produces too much of the hormone, thyroid, the number of bone loss and regrowth cycles increases. This results in incomplete cycles, in which the bone is never fully replaced, meaning more bone mass is lost than replaced, and with each cycle, more bone is lost.

Coeliac Disease

Coelic disease can interfere with the absorption of vital vitamins and minerals, such as Vitamin D and Calcium, by damaging the lining of the digestive system. This inability to absorb these nutrients, which are essential to bone health, can lead to osteoporosis.

Asthma

Asthma in itself does not cause osteoporosis, but because the long-term treatment of the condition usually requires steroids, which as we have already seen reduces the body’s ability to grow bone, this can impact on bone health.[5]

Lifestyle and Diet

Some of the factors which can affect bone density are unavoidable, such as menopause, and old age. But there are things we can do to minimise our chances of developing osteoporosis. Not only do people who prefer fizzy drinks tend to drink less bone-friendly liquids such as milk, but research conducted at Tufts University on several thousand men and women showed that women who drank more than three cola-based fizzy drinks per day had a 4% lower hip bone density than those who didn’t.[6]

Lack of exercise is another huge contributory factor in the development of osteoporosis. Any weight-bearing activity, such as walking or running, can help to maintain bone mass. Weight training is also beneficial, as the use of muscle also promotes bone building.

Regular drinking of alcohol can also add to the risk. Alcohol is a known diuretic, which means that essential minerals such as calcium are being eliminated through urine more rapidly, depleting the body’s supply. In addition, alcohol has been shown to decrease levels of magnesium and Vitamin D, both of which are important to bone health.

Likewise, a high intake of caffeine can also increase bone loss.[7]

Supplements

Calcium is essential to the development of bones, and 99% of the calcium we have is stored in our bones. When our diet is deficient in calcium, the body will ‘borrow’ it from the calcium bank in our bones, but unless we replenish those levels, bone density loss will continue.[8] The recommended daily allowance (RDA) for adults is 700mg, with post-menopausal women requiring 1200mg.[9]

Vitamin D and calcium go together like bread and butter. The main role of Vitamin D is the absorption of Calcium, so without it, the body cannot absorb enough calcium. With one in five people in the UK having low levels of Vitamin D, Public Health England (PHE) recommends that all adults and children over the age of one should take 10mcg Vitamin D supplement, particularly in the Autumn and Winter months when there is not enough sun exposure to manufacture the vitamin naturally.[10]

Manganese is a little heard of mineral, and yet its role in bone health is an important one. In post-menopausal women, the use of manganese has been shown to increase the bone density of the spine. As many women suffer from a deficiency after the menopause, supplementing their diet with manganese can go a long way towards the prevention of fractures and slowing down the progression of osteoporosis.[11]

The use of Copper bracelets in the treatment of arthritis has long been one of much debate, but there is little doubt that copper is important in bone health. Copper is vital for the production of collagen in the bones, which in turn is needed for the maintenance of bone density, and yet many of us are low in copper levels. Copper can be found in foods such as offal, shellfish, and nuts, but if they are not high on your list of preferred foods, taking a supplement of 1.2mg copper every day will keep your levels topped up.[12]

Zinc isn’t a mineral you would necessarily relate to bone health, and yet it is required for the mineralisation of bones. It has also been found to be important in the healing of broken bones, and keeps the immune system working and therefore protecting the bones from infection. Most importantly though it plays a vital role in the formation of new bone cells and the resorption of old. Over a period of four years, 392 men aged from 45 – 92 were studied, with researchers collecting data on diets, zinc levels, and bone densities. At the end of the study, it became apparent that the men with osteoporosis were also suffering from the lowest Zinc levels.[13]

Vitamin K works in synergy with Calcium and Vitamin D. By directing or guiding the calcium (which Vitamin D helps the body to absorb) to the bones, it not only gets the calcium to where it’s needed the most, but it also keeps it away from the arteries, thus preventing arterial hardening.[14] The RDA of Vitamin K is 1mg.[15]

In the same way as calcium, the majority of the body’s supply of Magnesium is stored in the bones. In cases of magnesium deficiency, it has been shown that bones are more brittle due to the mineral crystals in the bone becoming bigger. Magnesium accounts for around 1% of the bone tissue, so any decline in its level will have an adverse effect on bone density. The RDA for women over the age of 30 is 310mg, while this increases for men (420mg).

While the foundations for bone health are laid down in childhood and adolescence, there is still much which can be done to help adults slow down or reverse osteoporosis. By eating a healthy diet, and supplementing that diet with the relevant vitamins and minerals as mentioned above, bone density can be greatly enhanced. Fractures can seriously reduce mobility in later years, so doing everything possible now to maintain healthy bones will ensure an active life for much longer.

 

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