woman with vitamins
woman with vitamins
(Image credit: Rex Features (Shutterstock))

Are you always tired? Constantly marching purposefully from one room to another, only to discover you've completely forgotten the reason? Feeling more than a bit down in the dumps without being quite sure why? You may dismiss these all-too-common concerns as the inevitable results of stress, lack of sleep or growing older, particularly if you're peri-menopausal. But could there be another explanation? Some experts suggest that up to 4 in 10 of us could be suffering from some level of vitamin B12 deficiency. It's relatively straightforward to treat but, left unchecked, may result in permanent damage to the nervous system, heart failure, birth defects and dementia. Read on to find out whether you could have one, and what to do about it...

What is vitamin B12, and why do I need it?

Vitamin B12 affects the functioning of every cell in the human body. If we can't absorb enough, we can't produce healthy red blood cells or maintain a healthy nervous system. B12 works in synergy with vitamin B9 (commonly known as folic acid). This means that a deficit in either nutrient can cause problems. What are the symptoms of a vitamin B12 deficiency?

Symptoms include extreme tiredness, lack of energy, muscle weakness, pale skin, pins and needles or tingling in the fingers and toes, disturbed vision, diarrhoea, a sore red tongue and mouth ulcers. A vitamin B12 deficiency can also result in psychological problems, ranging from depression to problems with memory, understanding and judgement. These symptoms may prefigure the onset of dementia.

What causes it?

The most common cause of vitamin B12 deficiency in the UK is a condition known as pernicious anaemia. The cause of this condition is unknown, although it is most common in women around the age of 60. Pernicious anaemia causes the immune system to attack healthy cells in the stomach. This can prevent your body from absorbing the vitamin B12 in your food.

It's less common for the condition to result from a dietary deficiency, as most people consume sufficient B12 as part of their daily diets. However, vegans, vegetarians and fad dieters may be at greater risk, as the best sources of the vitamin are meat, fish, eggs and dairy products. It can take 2-4 years for symptoms to develop following a change in diet.

Some medical conditions, including Crohn's disease, may affect the body's ability to absorb vitamin B12, causing symptoms. Certain medications, including anticonvulsants and proton pump inhibitors (PPIs) can also limit absorption.

Simply getting older can also increase your risk of becoming B12 deficient, as natural stomach shrinkage results in decreased production of stomach acid - necessary for effective B12 absorption.

What are the potential complications?

Left untreated, a vitamin B12 deficiency can result in irreversible neurological damage, which may cause permanent movement, sensation or memory problems and even lead to dementia. It can also cause temporary infertility and result in complications and birth defects in pregnant women. In addition, long term B12 deficiency has been implicated in heart conditions and cardiac failure. How is it diagnosed?

If your GP suspects that you may be deficient in vitamin B12, you will be given a blood test. However, doctors often confuse the symptoms of vitamin B12 deficiency with those of other disorders, including depression, MS and even carpal tunnel syndrome.

Be aware that, if you are offered a blood test, the interpretation of results is controversial - in the UK, the threshold for diagnosis is 200 pg/ml blood, but experts warn that neurological damage "can begin at anything below 500". How is it treated?

Treatment for a severe vitamin B12 deficiency is usually by injection, given every other day until symptoms improve followed by 3-monthly top ups. Folic acid (B9) supplements may also be prescribed. For less severe deficiencies, supplements may be given in tablet form.

What should I do if I think I might have a vitamin B12 deficiency?

Visit your GP and request a blood test. If you're a borderline case and don't meet the threshold for a clinical diagnosis, you should be able to find B12 and folic acid supplements in any high street chemist. However, do ask to see your results - if your blood contains more than 500 pg/ml, taking supplements could do you more harm than good - high dose vitamin B12 and B9 supplements have been linked to an increase in cancer risk, and to foetal abnormalities in pregnant women.

Whether you have a clinical deficiency or not, you may benefit from increasing your intake of B12 and folate-rich foods. Beef, chicken, clams, oysters, salmon, trout, herring, crab and eggs are the best sources of vitamin B12 around. If you're vegan, try upping your intake of yeast extract (found in Marmite) and fortified breakfast cereals. Folate (or vitamin B9 - required for vitamin B12 to function correctly) is found in high quantities in green vegetables (such as broccoli, Brussels sprouts, peas, spinach, kale, asparagus and green beans), cauliflower, beetroot, carrots, squash, avocado, oranges, chickpeas, beans, lentils and nuts. Increasing your dietary B9 and B12 intake may also decrease your chances of developing cancer and heart disease.