Vitamin B12

All B vitamins help the body produce energy from food. Vitamin B12 also helps maintain healthy nerve cells and helps in the production of DNA, the body’s genetic material. B12 works closely with folate, to make red blood cells, to help iron work better in the body and to produce a compound involved in immune function and mood.

B12 deficiency can lead to serious health problems, especially in the very young. Symptoms include: extreme tiredness, lack of energy, pins and needles, muscle weakness, depression and cognitive problems such as impaired memory, understanding and judgement. A lack of B12 can lead to a raised level of the amino acid homocysteine in the blood which has been linked to CVD; this can affect meat-eaters, vegetarians and vegans. You can easily be tested by your doctor and a B12 deficiency may be treated with supplements or a course of injections. 

Vitamin B12 is a water-soluble vitamin that can be stored for years in the liver. Excess amounts leave the body in the urine. The UK government suggest an RNI of 1.5μg (micrograms) of B12 per day. In the US, the recommended amount is 2.4μg. However, a recent study suggested the ideal intake lies between 4-7μg per day (Bor et al., 2010). Another study suggested that a daily intake of between 6-10μg should ensure an adequate intake of B12 and minimise the build-up of homocysteine (Vogiatzoglou et al., 2009). 

In 2015, the European Food Safety Authority set a new ‘adequate intake’ dietary reference value for vitamin B12 of 4μg per day (EFSA, 2015). This figure was based on data from 13 dietary surveys in nine European Union countries and is based on preventing B12 deficiency and therefore may not represent the optimum intake. Erring on the side of caution, Viva!Health recommends an intake of 5μg per day from fortified foods with the regular use  of supplements to ensure topping this up. This is particularly important for children too. 

There are a number of different forms of B12:

  • Cyanocobalamin is a cheap and stable ‘inactive’ form used to fortify infant formula, breakfast cereals, vitamin drinks, plant milks and vegan meat replacements, as well as animal and fish feed. It is called inactive because it needs to be converted into an active form to work in the body. Tablets typically contain doses from as low as 2.5μg up to 1,000μg.   
  • Hydroxocobalamin is used as an injectable form of vitamin B12 that is given when there are problems with absorption. In the UK 1,000µg per dose is generally used.
  • Methylcobalamin is an ‘active’ form of vitamin B12. It costs more as it not so stable which is why it is provided in higher doses from 500-2,000μg. It needs to be stored away from light.   
  • Adenosylcobalamin is another ‘active’ form of vitamin B12, available as a supplement that needs to be stored away from light.

Hydroxocobalamin may be better for treatment by injection. Methylcobalamin and cyanocobalamin show very similar effects in the body, but on balance, cyanocobalamin may be superior as a supplement because of its stability (Obeid et al., 2015). US physician, author and internationally recognised speaker on public health issues, Dr Michael Greger says: “Unless you’re a smoker or have kidney failure, cyanocobalamin should be fine. That’s what I take!” (Greger, 2012). 

Vitamin B12 absorption can be reduced by a number of factors: poor functioning kidneys (McMahon et al., 2015); the diabetes drug Metformin and proton pump inhibitors (PPIs) which inhibit the production of stomach acid (Long et al., 2012); nitric oxide in cigarette smoke (Gabriel et al., 2006); nitrous oxide (laughing gas) used for anaesthesia or recreational use (Rusher and Pawlak, 2013) and heating food and drink in a microwave or other forms of cooking (Watanabe, 1998; Czerwonka et al., 2014).

The Department of Health cautions that if you take vitamin B12 supplements, you should not take too much, because this could be harmful. However, the amount they say you can take before it might be harmful is substantially higher than the RNI. They say that taking 2,000μg or less a day of vitamin B12 in supplements is unlikely to cause any harm (NHS Choices, 2015a).

B12 is made by bacteria in soil and water and to some extent bacteria in the gut (although production in the gut occurs in a different area to where absorption takes place). Traditionally farmed animals got B12 from eating food from the ground because B12 was in the bacteria in the soil. B12 consumed in their diet was then taken up into the cells in their bodies, which is how vitamin B12 ends up in red meat, fish, poultry, eggs and dairy products.

Vitamin B12 is also produced commercially in large vats where bacterial cultures are grown for its extraction. This type of B12 is used in fortified foods: veggie burger mixes, yeast extracts, margarines, breakfast cereals, soya milks and B12 supplements for humans and animals.

In modern society, fruit and vegetable production is far more sanitised in that fruit and vegetables are washed in chlorine for sale in supermarkets. This removes the B12-producing bacteria and so vegans must obtain vitamin B12 from fortified foods and/or supplements. Similarly, modern factory farming methods have changed the nature of the food farmed animals eat meaning that cattle and sheep now need B12 supplements too!

France accounts for 80 per cent of world production of cyanocobalamin (the most common and widely produced form of B12) producing more than 10 tons per year; over half of that (55 per cent of sales) are destined for animal feed, while the remaining 45 per cent is for humans (Kaesler, 2005). This makes the B12-reason to eat animal products somewhat invalid. For those who don’t like taking supplements, how is it any better to eat an animal that had been fed supplements? You could just cut out the middleman and get your B12 straight from the source, it’s easier to absorb that way too (see below).  

Plant foods, fermented soya foods and seaweeds do not provide a reliable source of B12 with the possible exception of the seaweed nori (Watanabe et al., 2014). However, this has yet to be confirmed by more substantive evidence. Until nori and other plant foods said to provide B12 are shown consistently to correct B12 deficiency, vegans should not rely on them for vitamin B12.

Vitamin B12 in meat is bound to animal protein and so is more difficult to absorb than the unbound form produced by bacteria. B12 deficiency tends to increase with age; up to 40 per cent of the UK’s meat-eating elderly population suffers from low B12 due to a reduction in their ability to absorb this vitamin (Tucker et al., 2000). In fact, mild to moderate B12 deficiency is common in industrialised countries despite the fact that a typical western diet provides around 5-7μg B12 per day (Obeid et al., 2015). This may be explained by an age-related decrease in the ability to release B12 from animal protein or by an impaired intestinal absorption of B12. The most common cause of B12 deficiency in the UK is the loss of intrinsic factor (a protein produced in the stomach) which may result from a genetic predisposition and tends to be age-related (Herbert, 1994). In the elderly, a decline in the amount of acid produced in the stomach can also reduce B12 absorption; again this mainly affects B12 absorption from meat. People with decreased gastric secretion often have difficulty digesting collagen, a major constituent of meat that is primarily digested by the enzyme pepsin, which could prevent the release of vitamin B12 from animal protein (Vogiatzoglou et al., 2009).  

Furthermore, while meat and meat products may contain vitamin B12, most meat is consumed after cooking, which can cause significant losses of B12 (Watanabe, 2007).

Studies suggest that the bioavailability of vitamin B12 from meat is lower than previously thought. This may be because of losses incurred in cooking or difficulty the body has freeing up B12 bound to animal protein. Either way, meat is not the best source of B12 and you are better off getting it from fortified foods and/or supplements. 

In the US, The Institute of Medicine of the National Academy of Sciences recommends that all adults over 50 years (including meat-eaters) obtain B12 from vitamin supplements or fortified foods because of the high incidence of impaired B12 absorption from animal foods in this age group (Institute Of Medicine, 1998). It could be argued that vegans have a heads-up on B12 as they routinely include a supplement or fortified foods in their diet. 


Food (medium portions) Vitamin B12 (μg)
RNI: 1.1μg/day for women and 1.3mg/day for men
Medium steak, fried (144g) 2.9
Meridian yeast extract (4g serving - enough for one slice of toast) 2.8
Soya milk - Alpro Soya Original (200ml) 2.5
Quarter pounder beef burger, grilled (78g) 2.3
Marigold Engevita with added B12 Yeast Flakes (5g) 2.2
Lamb chop, grilled (edible portion 70g) 2.1
Koko long-life dairy-free coconut drink (200ml) 0.8
Alpro Simply Plain Yoghurt 0.6
Fortified cereal* (40g) 0.8
Marmite (4g serving) 0.6
Vecon vegetable stock (1tsp/5g) 0.5
Pure Soya margarine (10g) 0.5
Bacon, grilled (46) 0.5

Note that some of the organic versions of these products are not fortified with B12.

*Many cereals fortified with B12 also contain vitamin D (D3) from lanolin, a substance obtained from sheep’s wool. At the time of writing, Tesco Malt Wheats, Sainsbury’s Wholegrain Malties and Waitrose Malted Wheats all contain 2.1μg of B12 per 100g and no vitamin D, so are suitable for vegans. Kellogg’s only use D3 at the moment but are looking into the possibility of using D2, which is suitable for vegans. 

Table 12.0 The vitamin B12 content of selected foods.

Source: FSA, 2002 and respective food packaging labels and company websites.

Table 12.0 shows the amount of B12 you can find in a range of meat and plant-based foods. Note that the 144g steak listed provides more than two times the daily 70g limit of red meat recommended by the government. It is quite easy to ensure your 5μg of B12 per day by including certain foods regularly in the diet; fortified cereal with soya or coconut milk, yeast extract, vegan spread, Vecon stock in soups and stews, a generous sprinkle of yeast flakes on your dinner and occasionally, certain fortified desserts (Alpro soya yoghurts and soya desserts contain B12). Of course, you need to ensure all these foods are the fortified varieties! Topping up once or twice a week with a supplement can be useful as a safety net to ensure you are getting sufficient B12.

A study in Switzerland found that despite a relatively low B12 intake from food in the vegan group they looked at, deficiency of this vitamin was low thanks to the widespread use of supplements. They concluded that consuming a well-balanced diet including supplements or fortified products, all types of diet can potentially fulfil requirements for vitamin and mineral consumption (Schüpbach et al., 2015).

B12 intakes among vegans are thought to be increasing, reflecting the increase in the number of B12-fortified products available coupled to a raised awareness. This will undoubtedly confer an advantage on vegans in later life who are used to ensuring sufficient B12 is present in their diet. It may be that vegans have gained an advantage in that they are used to routinely consuming B12-fortified foods and are therefore less likely to experience age-related B12 deficiencies.