Vitamin B12 & Vegan Diets

Vitamin B12 & Vegan Diets

One of the main arguments against vegan diets is that they do not provide vitamin B12, and so cannot be a nutritionally complete or healthful diet. In this blog post I dispel some popular myths about vitamin B12, explain why animal products do provide B12 but why this form of B12 is inferior to vegan supplements and why, in fact, even non-vegans should consider supplementing too. I hope this clears a few things up for those wondering why a vegan diet is deemed healthy despite not providing all necessary nutrients. I also hope this highlights the importance of this nutrient to those who are vegan (or actually, non-vegan too!) and currently not supplementing as a lot of this information is not known amongst the vegan community.

DISCLAIMER: please note that I am not (yet!) a medical professional so please see your GP or healthcare provider when considering supplements. This blog post aims to clear up common misconceptions around vegans needing to supplement because the diet is said to be ‘incomplete’, which is unfair. 

Why is vitamin B12 absent in vegan diets?

Vitamin B12 is recognised as the only vitamin not provided by the combination of a plant-based diet and adequate sun exposure. Vitamin B12 is only made by bacteria and not by animals or plants, though some animals such as cattle absorb vitamin B12 made by bacteria in their own digestive systems. It can also be found in the human intestinal tract, but it’s uncertain whether a sufficient quantity is absorbed to meet our needs.

Historically, vitamin B12 used to be found reliably in the soil and so people consumed traces through the soil that was not washed off their plants. However, today with our modern hygiene practices in agriculture and higher exposure to antibiotics and pesticides, the bacteria that makes B12 are no longer present in soil. Therefore, vegan diets are advised to take a B12 supplement or consume enough through fortified foods (mentioned later).

Why B12 is absent in plants

Grass-eating farm animals used to consume enough vitamin B12 as a consequence of consuming soil when grazing, so similarly to humans, they also cannot receive this source of B12 as they once could. Consequently, farm animals are supplemented with B12 in their feed, which is the B12 you’d be absorbing if you then consumed their flesh/milk/eggs. So if you are eating animal products, you are not obtaining a ‘natural’ or ‘made for us’ kind of B12 which vegans miss out on; you are consuming a supplement but through the middleman of an animal. As with most nutrients, vegans instead are just consuming the supplement directly, rather than through the inefficient vessel of an animal. 

Why vegan B12 sources are better than animal-based

In fact, obtaining B12 through a supplement or fortified foods is actually better than via animals, as vegan-friendly B12 sources are not bound to protein and so are more bio-available. Whereas, animal-based, protein-bound B12 rely on digestive enzymes and the stomach’s hydrochloric acid to break it down so it’s less able to be absorbed into the bloodstream. The vegan B12 sources are readily absorbed and don’t require this much digesting, meaning they’re also better for those with digestive issues.

This also indicates that those eating meat may not be meeting their B12 needs because an inadequate intake B12 is being absorbed, perhaps the reason why 40% of people in the US are B12 deficient (nowhere near that percentage are vegan!).

Why do we need B12?

Vitamin B12 is important for the maintenance of the nervous system as it:

  • contributes to the formation of myelin sheath, the insulating material around nerve cells
  • is needed for the production of several neurotransmitters which transfer signals between nerve endings.

It is also needed for the formation of red blood cells which transport oxygen around the body, and so is crucial in the performance of the body’s metabolism. Vitamin B12 is also required in the production of DNA.

Studies have shown the importance of B12 in the breakdown and removal of homocysteine, a substance produced as result of protein digestion. High blood homocysteine levels correlate with the presence of cardiovascular conditions and the formation of blood clots, so B12 is also important for cardiovascular health. 

Symptoms of a B12 deficiency

If not enough B12 is absorbed in the digestive system, it could lead to a B12 deficiency or ‘pernicious anaemia’. The production of red blood cells will be affected and so metabolism problems may present as fatigue and weakness, and the damage to the nervous system can lead to depression, low mood, symptoms similar to dementia or cognitive decline and poor memory or concentration.

Other symptoms include:

  • numbness or tingly feelings in the hands and feet
  • loss of appetite
  • sore and red tongue
  • long-term constipation. 

Getting enough

Vitamin B12 is needed in smaller amounts than any other vitamin; 10 micrograms is deemed sufficient per day for use, so a daily B12 supplement in tablet, liquid or spray form is sufficient. A 2000 micrograms of B12 supplement taken weekly would also provide an adequate intake. Many foods are fortified with the vitamin and so should also be abundant in your diet, such as fortified plant milks, yoghurts, cheeses, as well as nutritional yeast. However, frequent consumption of these fortified foods is needed to obtain enough B12 alone without other forms of supplementation. 

See this detailed article for more on doses. 

Vitamin B12 absorbance decreases as one ages (The Institute of Medicine in the US states “Because 10-30% of older people may be unable to absorb naturally occurring vitamin B12, it is advisable for those older than 50 years to meet their RDA mainly by consuming foods fortified with vitamin B12 or a vitamin B12-containing supplement.”), and infants are more likely to become deficient as they have little stores. 

I personally started off with Holland and Barrett’s Vitamin B12 capsules (or their B Complex), but I now use Vivo Life’s liquid B12 which you squeeze under your tongue rather than swallow, which is meant to be more absorbable.

All the plant-based milks I use in my porridge, tea and coffee are fortified (steer clear from the organic plant milks as they are not fortified) and I often have nutritional yeast in my meals too. Some cereals are fortified, but make sure to check online whether they are vegan though; most cereals fortify with animal-derived B12 and so makes the cereal non-vegan.

There is limited research on some plants such as mushrooms and seaweed being natural sources of plant-based B12, but currently these are seen as inadequate to meet needs.

Storage – do I have to take B12 as soon as I go vegan?

As much as 5mg of excess B12 can be stored in the liver at one time which can last up to five years, meaning your body could be using up B12 that you consumed as a non-vegan. This is because the body only needs around 0.2% of this to be released every day in order to function efficiently. Without any form of B12 dietary intake, symptoms of deficiency can take up to 5 years to show as your body can rely on these stores. But everybody is different, and people absorb and/or use up their stores at different rates so you should not rely on this. Finally, symptoms of a B12 deficiency are not always consistent or clear so it is important that you do not wait until your stores are likely to be used up before considering supplementation. 

I hope this has been informative and helpful for you! Look out for upcoming blog posts on other nutrients commonly seen as harder to get through, or evidence of the downfalls of, a vegan diet.

The Conscious Medic

This Post Has One Comment

  1. George Theresa

    This article provides a thorough review of the scientific literature on vitamin B12 and the vegan diet—it includes every important study on vegans published since 1980. If you have a question about whether it’s okay to cut supplements in half or combine supplements to achieve the dose we recommend, the answer is “Yes.” Be aware that nutrient recommendations are only estimates—it’s not necessary to consume the exact amount we recommend every single day.

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