Megaloblastic anaemia

The term 'megaloblastic anaemia' incorporates two different types of anaemia – vitamin B12 deficiency anaemia and folate deficiency anaemia. Most people with either of these conditions will have underdeveloped, larger than normal red blood cells. These do not function properly and will crowd out the healthy cells, which leads to anaemia. Also, because they are underdeveloped, they will have a shorter than normal life expectancy.

Megaloblastic anaemia is typically diagnosed with a blood test and can be treated by a change in diet to feature foods high in vitamin B12 or folic acid (the artificial form of folate). If you have the condition, your GP may also prescribe vitamin B12 or folic acid supplements alongside a diet change.

In this fact sheet we will explore the two most common forms of megaloblastic anaemia, highlight their symptoms, causes and find out how a nutritionist can help with the conditions.

Vitamin B12 deficiency anaemia

Vitamin B12 deficiency anaemia is a type of megaloblastic anaemia along with folate deficiency anaemia. This condition is a result of a deficiency in vitamin B12. It causes red blood cells to become larger and less efficient at carrying oxygen.

Vitamin B12 is structurally the most complex of all vitamin molecules and carries out a number of functions additional to red blood cell formation. One other purpose of vitamin B12 is to help maintain a healthy nervous system. This explains why a deficiency in vitamin B12 can cause numbness or altered sensations.

What are the symptoms of vitamin B12 deficiency anaemia?

This form of megaloblastic anaemia will share symptoms of other types of anaemia, such as:

  • tiredness
  • lack of energy
  • insomnia
  • feeling faint/giddy
  • breathlessness, particularly on exertion.

Other symptoms that are linked to the lack of vitamin B12 include:

  • a loss of appetite
  • a sore tongue and mouth
  • depression
  • diarrhoea
  • forgetfulness and reduced concentration levels
  • affected vision.

These symptoms could be caused by problems that are not related to vitamin B12 deficiency anaemia. If you think you have any of these symptoms, contact your GP.

What causes vitamin B12 deficiency anaemia?

Pernicious anaemia

The most common cause of this condition in the UK is pernicious anaemia. This typically develops when your body lacks a certain protein called intrinsic factor. Cells in your stomach release the intrinsic factor, which then attaches to the vitamin B12. This combined vitamin B12/intrinsic factor is then absorbed into your bloodstream when it enters your small bowel.

Pernicious anaemia is classified as an autoimmune disease. The immune system creates antibodies to attack viruses and germs, but in this case the antibodies fight against the intrinsic factor, or against the cells that create the intrinsic factor.

Pernicious anaemia is most common in women over the age of 50, and it tends to be genetic. It’s also more common in people who have other autoimmune diseases such as Addison’s.

Gut or stomach problems

Although uncommon, gut or stomach problems can cause a vitamin B12 deficiency. These causes include:

  • Diseases that affect the stomach, such as Crohn's.
  • Removing the end of the small intestine or the stomach.
  • Stomach conditions that affect the creation of the intrinsic factor, such as atrophic gastritis.

Medicine

Some medicines can affect the absorption of vitamin B12 into your body. One of the most common is a diabetes medicine called metformin. Others include neomycin, colchicine and some anticonvulsant medicine that is used for epilepsy.

Diet

If you eat a balanced diet, the food and drink you consume will not likely cause vitamin B12 deficiency. If you are a strict vegan however, the lack of animal and dairy products may do.

Diagnosing the condition

Your GP will ask you questions about your symptoms and your medical history. If he or she suspects you might have anaemia, your GP will then conduct a blood test.

Your blood will be tested for:

  • The correct levels of haemoglobin.
  • Iron, folate and vitamin B12.
  • The shape of your red blood cells.
  • Intrinsic factor antibodies.

If your doctor cannot find the cause of the anaemia, you may have to undergo further tests. You may be referred to a gastroenterologist (a specialist in conditions in the digestive system) or a haematologist (a specialist in blood conditions).

Treating the condition

Your doctor will try to find the cause of your vitamin B12 deficiency, and then will start you on treatment.

Medicine

Depending on the cause, your GP may suggest taking supplements of vitamin B12. The recommended dose to be taken is typically between 50 to 150 milligrams between mealtimes. After eight weeks, your doctor will want to check your vitamin B12 levels.

In some cases, supplements may not be beneficial for your situation. Your GP might suggest having injections of vitamin B12 into a muscle instead. However there are possible side effects that can occur after taking these injections. They include:

  • a skin rash
  • feeling sick
  • a headache
  • feeling dizzy.

If you have difficulty absorbing vitamin B12, i.e. if you have pernicious anaemia, you may need to have injections throughout your entire life. These will need to be administered every two to three months.

Foods high in vitamin B12

Although uncommon, consuming a diet that lacks vitamin B12 might trigger vitamin B12 anaemia. Your GP may advise you to adjust your diet or refer you to a nutritionist for advice on preparing a specific diet plan to increase your intake of foods high in vitamin B12.

Foods high in vitamin B12 include:

  • red meat
  • animal products such as cheese and eggs
  • yeast extract
  • fortified bread
  • fortified breakfast cereals
  • salmon.

Folate deficiency anaemia

Folate deficiency anaemia is a condition that you can get if you have a lack of folate in your body. Folate, or vitamin B9, is responsible for many processes in your body. For example, it combines with vitamin B12 to help create DNA. It’s also crucial in creating red blood cells. So if you do not have enough folate in your body, it won’t be able to create as many red blood cells as it would normally. The cells will also be larger than normal and won’t last as long.

If you lack the regular amount of red blood cells, your organs and tissues may not acquire enough oxygen. This can lead to symptoms of anaemia.

What are the symptoms of folate deficiency anaemia?

This type of megaloblastic anaemia shares the following symptoms with other forms of anaemia:

  • tiredness
  • shortness of breath (particularly on exertion)
  • heart palpitations.

Other symptoms that are linked to the lack of folate deficiency anaemia include:

  • a loss of appetite
  • feeling tired
  • depression
  • diarrhoea.

These symptoms could be caused by problems that are not related to folate deficiency anaemia. If you think you have any of these symptoms, contact your GP.

What causes folate deficiency anaemia?

There are a number of likely causes of folate deficiency. Here are the most common:

  • Diet – Not eating enough foods high in folic acid is one of the most common causes. This typically occurs in older people who do not stick to a balanced diet. Another group of people who might be susceptible to a poor diet are those who drink a lot of alcohol.
  • Pregnancy – This causes your growing baby to consume your reserve of folate. You are more at risk of using up your folate reserves in the latter stages pregnancy. The risk increases if you do not eat a balanced diet containing foods high in folic acid.
  • Gut conditions – Although uncommon, some conditions of the gut can cause poor absorption of folate. Such conditions include coeliac disease.
  • Blood disorders – Particular blood disorders such as sickle cell disease can lead to a high turnover of red blood cells.
  • Inflammatory conditions – Although less common than other causes, some inflammatory conditions, such as Crohn’s disease, can trigger low folate levels.
  • Medicine – Certain medicines can affect your absorption of folate. So you may have to take extra forms of folic acid when on these medicines. These medicines include methotrexate, sulfasalazine and cholestyramine.

Diagnosing the condition

Your GP will ask you questions about your medical history and your symptoms. If your doctor suspects you might have anaemia, he or she will then conduct a blood test.

Your blood will be tested for:

  • The correct levels of haemoglobin.
  • Folate, iron and vitamin B12.
  • The shape of your red blood cells.
  • Intrinsic factor antibodies.

If your GP cannot find the cause of the anaemia, you may have to undergo further tests. You may be referred to a haematologist (a specialist in blood conditions) or a gastroenterologist (a specialist in conditions in the digestive system).

Treating the condition

Your doctor will try to find the cause of your folate deficiency, and then will start you on treatment.

Medicine

Depending on the cause, your GP may suggest taking folic acid supplements. These can be either bought over the counter, or your doctor can prescribe them. Before you are prescribed the supplements, your GP will need to check your levels of vitamin B12, as folic acid supplements can hide vitamin B12 deficiency from future blood tests. This can lead to problems with your nervous system.

Folic acid is the artificial form of folate. Typically, you will take 5 milligrams per day for a minimum of four months. In some cases people will need to take folic acid for an extended length of time, and sometimes for the rest of their lives. 

If you do take folic acid to treat anaemia, your doctor will need to track your folate level and blood count. You will need to take a blood test around eight weeks after you begin taking the supplements. Then you will need another blood test after the treatment to ensure you have responded to it.

Foods high in folic acid

A lack of foods high in folic acid may cause folate deficiency anaemia. If you’re not consuming enough folic acid in your diet, a nutritionist may be able to help. They can structure your diet to include some of the following foods to address this:

  • chickpeas
  • oranges
  • pork
  • poultry
  • brown rice
  • green vegetables.

How can a nutritionist help with vitamin B12 and folate deficiency anaemia?

It can be very draining if you are feeling tired on a daily basis. So to prevent and treat folate or vitamin B12 deficiency anaemia, it’s advised that you eat a balanced diet that contains a number of folic acid or vitamin B12 rich foods. A nutritionist will be able give you a personalised meal plan with all the nutrients needed to improve your quality of life. This will help alleviate the pressure of finding food to create the perfect diet.

Before making any radical changes to your diet please consult your GP.

Content reviewed by dietitian, Leo Pemberton. All content displayed on Nutritionist Resource is provided for general information purposes only, and should not be treated as a substitute for advice given by your GP or any other healthcare professional.

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