Osteomalacia

About osteomalacia

Bone development

Healthy bone consists of an outer shell and an inner strong mesh (matrix) made of protein and minerals (particularly calcium). Throughout your lifetime, your bones continuously maintain and repair themselves. This is done through a process called ‘bone turnover’, during which tiny areas of old bone are removed and replaced with new bone.

The strength of your bones depends on the amount of minerals laid down in the matrix. This is done through a process called mineralisation. Minerals such as calcium and phosphorus are absorbed from the food you eat and deposited in your bones. You also need vitamin D for this process because it helps your body to absorb calcium and makes sure it gets to where it's needed (eg your bones or teeth).

As a child, mineralisation helps your bones to grow and develop, whereas as an adult, it’s needed to maintain and repair them.

Osteomalacia

Osteomalacia develops when your bones don't get enough of the minerals they need. This makes your bones soft and weak, and can crack or break more easily, and can cause deformities.

Osteomalacia affects adults. A similar condition that affects children’s bones is called rickets.

In the UK, osteomalacia commonly affects people of South Asian origin and people over 65.

Symptoms of osteomalacia

The symptoms of osteomalacia can be quite subtle. However, specific things to look out for include:

  • pain in your bones, especially in your hips, groin, legs and feet – if you have a minor knock to your bone, it can feel unnaturally painful
  • backache
  • muscle weakness, especially in your thighs, torso and shoulders – you may find it difficult to get up from a chair or climb stairs

Osteomalacia can sometimes be caused by other conditions, such as kidney or liver disease. Often, it's the symptoms of these other conditions that are picked up first and later lead to a diagnosis of osteomalacia.

Complications of osteomalacia

If you have osteomalacia, you may be more at risk of fractures. Stress fractures are tiny cracks in your bone. These can often be the cause of bone pain and can lead to complete fractures.

Causes of osteomalacia

Osteomalacia is usually caused by a prolonged lack of vitamin D. You can also get it if you have an underlying health condition that affects mineralisation.

Vitamin D deficiency

Vitamin D is important for bone health. Vitamin D is produced naturally by your body when your skin is exposed to sunlight and can also be obtained from some foods, such as oily fish.

In the UK, up to a quarter of the population has low levels of vitamin D in their blood.

You’re more at risk of developing a vitamin D deficiency that may lead to osteomalacia if you:

  • cover up extensively with clothing (for example, by wearing a burka)
  • don't spend much time outside
  • use a lot of sunscreen
  • are aged 65 or over
  • have a poor diet (lacking in vitamins and nutrients) or eat a restrictive diet (eg if you’re vegetarian or vegan)
  • are pregnant or breastfeeding
  • are under the age of five

You’re also more at risk if you have dark skin (for example people of African, African-Caribbean and South Asian origin) and live in a climate that has fewer hours of sunlight per day – such as the UK – compared with countries near the equator. The darker your skin, the less likely you are to get enough vitamin D from the milder climate.

Less commonly, vitamin D deficiency can be caused by underlying health conditions, such as:

  • malabsorption – when your body can’t properly absorb certain nutrients (it can happen if you have a condition such as coeliac disease or chronic pancreatitis, or it can be caused by some stomach surgery procedures, such as a gastric bypass
  • liver disease
  • kidney disease

Vitamin D deficiency can also be a side-effect of some epilepsy medicines, such as carbamazepine, phenytoin and sodium valproate.

Phosphate deficiency

Occasionally, osteomalacia can be caused by a lack of phosphate in your body. This stops your bones mineralising properly. If you take certain antacid tablets (such as aluminium hydroxide) over a long period of time it can lower the levels of phosphate in your body. Kidney disease or a rare inherited disease called hypophosphataemic rickets can also cause your phosphate levels to fall.

Mineralisation defects

This is when the cells that lay down the minerals in your bones during the mineralisation process don't work properly.

Diagnosis of osteomalacia

Your GP will ask about your symptoms and examine you. If your GP thinks you have osteomalacia, he or she will ask you to have a blood test. This will measure the levels of vitamin D, calcium and phosphate in your blood. Your GP may refer you to a hospital for an X-ray to check for stress fractures, especially if any parts of your body are painful or tender.

Your GP may refer you to a specialist for treatment or monitoring if there is no obvious cause of osteomalacia or you don't respond to treatment. If you have an underlying condition that needs further treatment, your GP may also refer you to a specialist.

If osteomalacia is caused by phosphate deficiency, a problem with mineralisation of your bones, or another underlying condition, your GP may refer you to a doctor who specialises in metabolic bone disease.

Treatment for osteomalacia

If osteomalacia is caused by a lack of vitamin D, your GP will prescribe you daily vitamin D and possibly calcium supplements. If your osteomalacia is severe or you have problems remembering to take your tablets, he or she may recommend that you have vitamin D injections or take a higher dose of supplements.

Vitamin D and calcium supplements can cure osteomalacia. However, you may still have bone pain and muscle weakness for several months after you start your treatment.

You may need to continue to take vitamin D supplements for the rest of your life, depending on your lifestyle and where you live.

It's important that you don’t take more than the dose of vitamin D supplement that your GP recommends. If you have too much vitamin D, you may develop vitamin D toxicity and hypercalcaemia, which is an excess of calcium in your body.

Always read the patient information leaflet that comes with your supplements and if you’re pregnant or breastfeeding, ask your pharmacist or GP for advice first. Talk to your GP before taking vitamin D supplements if you’re taking diuretics for high blood pressure or have a history of kidney failure.

Prevention of osteomalacia

There are several things you can do to reduce your risk of osteomalacia.

Diet

Make sure that you eat foods that are rich in calcium and vitamin D.

Good sources of calcium include:

  • dairy products (for example, milk, yoghurt and cheese)
  • bread made with fortified flour
  • soya beans and tofu
  • leafy green vegetables (for example, broccoli and cabbage but not spinach)
  • fish (which you also eat the bones) such as sardines and pilchards

Diet alone isn't usually enough to give you your daily requirement of vitamin D. However, you can get some vitamin D from:

  • oily fish (for example, sardines, mackerel and fresh tuna)
  • eggs
  • breakfast cereals that are fortified with vitamin D
  • margarine

Sun

You may get enough vitamin D during summer by spending frequent short spells in the sun without wearing sunscreen (the exact time you need is different for everyone, but is typically only a few minutes each day in the middle of the day). However, don’t let your skin redden and follow sun safety advice.

Supplements

If you don't get much sun exposure and particularly during winter months, taking up to 25 micrograms of vitamin D a day (two high-strength 12.5 microgram capsules) can help to make sure you get enough.

Always read the patient information leaflet that comes with your supplements and if you’re pregnant or breastfeeding, ask your pharmacist or GP for advice first. Talk to your GP before taking vitamin D supplements if you’re taking diuretics for high blood pressure or have a history of kidney failure.

Why are people aged 65 or over more at risk of developing osteomalacia?

Answer

If you're aged 65 years or over, you’re more likely to develop osteomalacia, often referred to as age-related osteomalacia. This is generally because you will get less calcium and vitamin D from your diet and you won’t get as much vitamin D from sunlight as you used to.

Explanation

As you get older your metabolism changes and you may become less mobile. This can put people aged 65 and over at risk of developing age-related osteomalacia. Also, as you age, your skin can’t process vitamin D as efficiently as it used to.

A major cause of osteomalacia is a diet lacking in vitamin D. As you get older, you're less able to absorb all the nutrients you need from food. Also, if you live on your own, you may be less inclined to cook and eat a varied diet so it may lack important vitamins and nutrients.

As you get older, it's possible that you will find it more difficult to get around. This may mean you can't go out without help or that you have to move into a care home. If you can't get outside in the sunlight, you may develop vitamin D deficiency, which could lead to osteomalacia.

If you're over 65, take daily vitamin D and calcium supplements. Taking up to 25 micrograms of vitamin D a day (two high-strength 12.5 microgram capsules) can help to make sure you get enough.. In some care homes, vitamin D and calcium supplements are given to elderly residents to help reduce the risk of falls and fractures. With osteomalacia, as bones soften and weaken, you may become more frail and less stable, making it more likely that you will fall and break a bone.

Why are people of Asian, African-Caribbean or Middle Eastern descent more likely to get osteomalacia?

Answer

Osteomalacia is more common in people of Asian, African-Caribbean or Middle Eastern origin for two reasons – exposure to sunlight and diet.

Explanation

The darker your skin, the more sunlight you need to get enough vitamin D. This means if you're of Asian, African-Caribbean or Middle Eastern origin, you're more at risk of developing osteomalacia because sunlight in the UK isn't strong enough to give you the amount of vitamin D you need, especially during the winter months when the sun is much weaker. Diet is also a factor, although much less so than sun exposure.

If you completely cover yourself for religious reasons, for example by wearing a burka, or you never go outside into the sunlight, you're also at risk of vitamin D deficiency. This is because the sunlight is prevented from getting to your skin.

Another cause of osteomalacia is a diet that lacks vitamin D and calcium. If you eat a diet that is low in nutrients or a restrictive diet (eg vegetarian or vegan) you may miss out on vital vitamins and minerals. Cultural differences in diets can mean that certain nutrients are missed in certain communities. For example, chapatti flour can prevent calcium being absorbed by the stomach. Because of this, some brands of chapatti flour now have added vitamin D.

A diet that is low in vitamin D and calcium coupled with limited exposure to the sun puts you at a greater risk of developing osteomalacia. Taking up to 25 micrograms of vitamin D a day (two high-strength 12.5 microgram capsules) can help to make sure you get enough.

Always read the patient information leaflet that comes with your supplements and if you’re pregnant or breastfeeding, ask your pharmacist or GP for advice first. Talk to your GP before taking vitamin D supplements if you’re taking diuretics for high blood pressure or have a history of kidney failure.

Can vitamin D or calcium supplements affect other medicines that I'm already taking?

Answer

Yes, certain medicines, such as those used for epilepsy, or diuretics used to treat high blood pressure can interact with vitamin D and calcium supplements. This means that either the medicine you're taking can be affected by the supplements, or the supplements may not work as well if you're taking a certain medicine. It's important to talk to your GP or pharmacist before taking vitamin or mineral supplements.

Explanation

Vitamin D and calcium supplements are very effective at treating and preventing osteomalacia. However, if you’re already taking medicines for other conditions, you may need to be careful about how they interact with vitamin and mineral supplements.

Medicines for epilepsy such as carbamazepine, phenytoin and sodium valproate, and some anti-inflammatories (corticosteroids) can lessen the effect of vitamin D supplements. If you're taking vitamin D supplements to treat or help prevent osteomalacia, this means they will be less effective and you may need to take more than usual. However, don't increase your dose of any medicines without talking to your GP first.

Diuretic drugs for high blood pressure can increase the effect of vitamin D and calcium supplements. This can increase your risk of having too much calcium in your blood (hypercalcaemia), which can cause kidney stones and may also affect your digestive system leading to symptoms such as constipation. Your GP will need to monitor you carefully if you're taking these medicines with vitamin D supplements. He or she will check the calcium levels in your blood on a regular basis.

Calcium supplements can also affect your body's ability to absorb some medicines, meaning they may be less effective. Some of medicines that may be affected include:

  • levothyroxine, which is used to treat an underactive thyroid
  • bisphosphonates, which are used to treat osteoporosis and some cancers
  • sodium fluoride, which is used to prevent tooth decay
  • some antibiotics including tetracycline
  • iron supplements

If you're taking any of these medicines, it's important to talk to your GP or pharmacist before taking calcium supplements.