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Vitamin B12 is an extraordinary vitamin.

It is needed in much smaller amounts than most other known vitamins. And is the only vitamin that can’t be reliably supplied by a varied wholefood plant-based diet and regular exposure to the sun.

The story of vitamin B12 is complex and fascinating.  Here we take a look at this extraordinary nutrient, where it comes from and why you need it. We also delve deeper into the reasons why so many people aren’t getting enough, the warning signs that you might be running low and what you can do to correct a deficiency.

What does it do?
Vitamin B12 (cobalamin) is needed for well over 100 daily functions. Here’s just a few:

 • Helps the blood carry oxygen
 • Helps your body to make use of protein and fats
 • DNA synthesis
 • Essential for healthy nerves
 • Helps your body to deal with toxins
 • Foetal development during pregnancy

Where does it come from?
Just like all the other B vitamins, B12 is water-soluble and needs to be regularly supplied by your diet. You’ll find vitamin B12 in rich supply in animal products such as grass fed beef, dairy products, eggs and fish. Hence why strict vegans are at a much higher risk of deficiency.

How vitamin B12 is absorbed…(this is the crucial bit)
Vitamin B12 enters the body attached to amino acids in protein foods. It’s only when it comes into contact with stomach acid that it comes unstuck and can then be absorbed into the system. So stomach acid is a crucial part of the process. 

And that’s only part of the story…

Intrinsic factor is a protein secreted by the cells of the stomach lining. It attaches to unbound B12 and takes it to the intestines to be absorbed. Only at this point can vitamin B12 get to work on its many bodily functions.

To achieve optimal B12 you need:
1)     To get enough in your diet (animal foods, fortified foods or supplements)
2)     To have good levels of stomach acid
3)     To be producing intrinsic factor

Symptoms of B12 deficiency
A mild deficiency may not cause any symptoms. Symptoms tend to develop slowly and may not be recognised immediately. Initial signs of low B12 may include slightly elevated homocysteine and methylmalonic acid (MMA) levels.

As the problem worsens, symptoms can include:

 • Low energy, chronic fatigue
 • Weakness
 • Lightheadedness
 • Heart palpitations and shortness of breath
 • Pale skin
 • Poor dental health including bleeding gums and mouth sores, sore red tongue, mouth ulcers
 • Yellowing of the skin
 • Constipation, diarrhoea, nausea, loss of appetite, or gas
 • Nerve problems like numbness or tingling, muscle weakness, and problems walking
 • Joint pain
 • Vision loss
 • Mental problems like depression, memory loss, or behavioural changes
 • Poor concentration

Who’s most at risk of deficiency?

 • Anyone regularly taking stomach-acid reducing medications (antacids, H2 receptor antagonists, proton pump inhibitors)
 • Anyone with low stomach acid
 • Anyone taking metformin (oral diabetes medicine that helps to control blood sugar levels)
 • Elderly people (stomach acid production tends to reduce with age)
 • Vegans / Vegetarians
 • Smokers (nicotine can block absorption)
 • Alcoholics
 • Those frequently using antibiotics
 • Anyone with digestive disorders such as Crohn’s or coeliac disease
 • Anyone with stomach ulcers
 • Anyone who has had weight loss surgery / any other operation where part of the stomach or small intestine is removed
 • Those with atrophic gastritis – thinning of stomach lining affects intrinsic factor production
 • Anyone with Pernicious anaemia – autoimmune condition affecting intrinsic factor production
 • Those with an overgrowth of intestinal bacteria or parasites

What to do if you suspect a deficiency
Vitamin B12 levels are usually tested with a simple blood test. Test results can be inaccurate however since large amounts of B12 are stored in the liver. Also, taking large amounts of folic acid can mask a B12 deficiency so this needs to be taken into account. Studies suggest that 50% of patients with diseases related to B12 deficiency have normal B12 levels when tested.

If you suspect a deficiency, but tests have come back normal, secondary tests such as checking your homocysteine (HC) and or methylmalonic acid (MMA) levels can be useful. A deficiency of B12 at the tissue level can lead to elevation of both MMA and HC even when serum vitamin B12 is found within the reference range1.   

How to correct B12 deficiency – supplements or injections?
With proper treatment, symptoms of B12 deficiency usually begin to improve in days.  The cause of B12 deficiency will influence the way it is treated.

People with pernicious anaemia or those who may struggle to absorb vitamin B12 will usually be offered injections as a way to boost levels and may need to continue having injections every 1-3 months indefinitely, depending on whether the cause can be resolved.  

In vegans and other people whose B12 deficiency is diet related, oral B12 supplements and a diet designed to increase consumption of B12 is usually recommended to boost levels. 

Why are B12 & folate usually recommended together?
B12 and folate work together so are usually recommended as a combination in supplement form.

Which form to take?
B12 is best supplemented in the activated form of methylcobalamin along with the highly bioavailable form of folate - 5-methyltetrahydrofolate. You can also take intrinsic factor in supplement form to support the absorption and assimilation of B12. Vitamin B12, folate & intrinsic factor work well together to support optimal levels in those who are low. 

Best food sources of B12

 • Grass-fed beef
 • Lamb
 • Dairy products
 • Eggs
 • Oysters
 • Sardines
 • Tuna
 • Turkey
 • Chicken

Worried you might be deficient? Get your levels checked…
Symptoms of B12 deficiency, especially the more common ones such as low energy and constipation, can be symptomatic of so many different health problems that low B12 can often be difficult to spot. It is however, an incredibly important nutrient and crucial that you keep your levels within a healthy range. If you are even slightly concerned that you might be low, it’s worth a quick trip to your GP for further investigation, especially if you’re at higher risk because of your age or other factors such as regularly taking antacids or suffering from gastrointestinal problems that affect absorption. Remember that up to 50% of people struggling with diseases related to B12 deficiency may have normal blood levels when tested1, and further testing of homocysteine (HC) and methylmalonic acid (MMA) may also be required to rule deficiency in or out. The good news is that it’s relatively easy to correct once it has been identified and can have widespread positive effects on many different aspects of your health once your levels are back up to normal.   

1. Vashi P, Edwin P et al. Methylmalonic acid and homocysteine as indicators of vitamin B12 deficiency in cancer. PLOS One January 25, 2016. https://doi.org/10.1371/journal.pone.0147843 

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