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Vitamin B12 – what every vegetarian and vegan needs to know

Vitamin B12 is essential for our mental health. What’s more, a deficiency in B12 can show up as mental health symptoms without any of the usual physical symptoms of this vitamin deficiency. This means it can go undiagnosed and untreated by health professionals. If you are vegetarian or vegan you are at increased risk of vitamin B12 deficiency. Here’s what you need to know…..

Why do we need vitamin B12? 

Vitamin B12 is essential for our mental and physical health. If we are deficient in vitamin B12 this can often result in anaemia, leading to feelings of unexplained tiredness and exhaustion. However, vitamin B12 deficiency can also lead to nerve damage (irreversible if not caught early) and can show up as a range of mental health symptoms. Vitamin B12 deficiency can result in delusions, symptoms of depression and even dementia like symptoms. This does not mean that everyone with these symptoms has a vitamin deficiency; but it does mean that some people who appear to have a mental illness in fact have an easily corrected vitamin deficiency. It is also possible that someone’s existing mental health problems are made worse by a deficiency of vitamin B12. As I mentioned at the start of this post, one of the challenges is that you can have the mental health symptoms of B12 deficiency without the physical symptoms – which makes it easy for a doctor to miss.


If you eat meat and/or fish regularly then you will be getting sufficient vitamin B12 from your diet. You could still be at risk of vitamin B12 deficiency but this is because of issues with absorption and metabolism. This could be caused by the autoimmune disease pernicious anaemia; low stomach acid; by long term use of the antacid medications known as proton pump inhibitors (including omeprazole and lansoprazole); the type 2 diabetes medication metformin or by use of a gastric band. If you are concerned you may be deficient for any of these reasons then you should seek medical advice.


Vegetarians and vegans may not have any absorption issues but may find they are not getting enough vitamin B12 from their diet. This is because there is no reliable source of vitamin B12 in plants. Some plant sources like seaweeds contain vitamin B12 – just not in a form that we can use! Vitamin B12 is stored in the liver for up to four years. This means you can switch to a vegetarian or vegan diet and feel real health benefits from this. You then develop symptoms of deficiency which you don’t associate with your diet because you made the changes such a long time ago!

If you are vegetarian you can get vitamin B12 from eggs and dairy. You need to consider how often you are including these foods in your diet. If you are concerned that you only eat these foods occasionally then you may wish to monitor your levels of vitamin B12 to make sure you do not need to be supplementing. If you are vegan then you will need to supplement. You can either do this by taking vitamins or through fortification (where the vitamin supplement is added to foods such as nutritional yeast). If you are going the fortification route then make sure you familiarise yourself with food labels so that you know you are getting enough. Your marmite on toast is only going to meet a quarter of your daily needs.

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