Vitamin B12 binds to a protein in our stomach, called intrinsic factor and is absorbed in the small intestine. People who follow vegan diets are vulnerable to deficiency, and some studies have shown some people following a vegetarian diet can also have low vitamin B12 levels.
How much vitamin B12 do we need each day?
Our daily vitamin B12 requirements are incredibly low – an adult requires just 2.4 micrograms. Pregnant women have slightly higher needs. One glass of cows’ milk meets about half of our daily requirements, as does one glass of a fortified non-dairy milk alternative – a suitable choice would have at least 1 microgram of B12 per 250mL.
Consuming some animal products such as eggs, meat, fish, chicken or dairy is also a good way to meet your daily intake of B12 – two eggs provide about 1.2 micrograms, or half of the daily requirements for adults. However, if you choose not to consume any or very few animal products, we recommend taking a B12 supplement containing cyanocobalamin daily.
Vitamin B12 deficiency
Vitamin B12 deficiency is common in people following vegan diets because plant-based foods do not contain adequate B12. Vitamin B12 deficiencies often manifest with neurological symptoms or megaloblastic anaemia which is when red bloods cells fail to mature and are larger than expected.
Neurological symptoms of vitamin B12 deficiency can be as far reaching as general weakness, difficulty controlling the bladder and bowel, memory loss, numbness or tingling in the hands or feet, and even dementia, depression, psychosis and seizures. It can be very serious if we do not take adequate action to ensure regular intake and many of the symptoms are irreversible even once the deficiency is treated.
Vitamin B12 and a vegan diet
Vitamin B12 is the only nutrient that is not readily available from plant-based sources, so extra care needs to be taken to ensure you're meeting your needs. Vitamin B12 is synthesised by bacteria, algae, fungi and other microorganisms.
Plant and animals are not able to make it, but animals do consume these microorganisms and as such it is found in their meat, milks and eggs. So, if you are following a plant-based diet or consume very few animal products, you will need to frequently consume foods fortified with B12, such as plant-based milks, yoghurts, or cereals (check the ingredients list, learn how to read ingredients lists here) or nutritional yeast.
Our bodies can store B12 for 3 to 5 years, so people following a vegan diet and not regularly taking B12 supplements may not realise they're not consuming enough for quite some time. Eat Sustainably recommend you seek seeking individual advice from an Accredited Practising Dietitian or your GP if you are pregnant, breastfeeding or have children on vegan diets.
Food sources of Vitamin B12
Vitamin B12 is naturally found in animal products and many foods are now also fortified. Some vitamin B12 is found in seaweed, such as nori, but the amounts are too small to make a significant contribution to your daily requirements (and too much seaweed can lead to excessive intake of iodine and salt).
Consuming adequate amounts of vitamin B12 in food is the best way to maintain healthy levels, and given the seriousness of deficiencies, many products that are regularly consumed on a vegan diet are now fortified in Australia.
Some examples of Vitamin B12 sources of food are:
- 100g mussels = 6.3 ug
- 100g salmon = 2.3 ug
- 100g beef = 1.8 ug
- 100g cheddar cheese = 1.7 ug
- 100g eggs (2 large) = 1.4 ug
- 100g chicken breast = 0.2 ug