Following any form of a restricted diet means that some individuals may have to work harder to ensure that all important dietary requirements can still be met. Vegans and strict vegetarians are two particular groups who can often be at risk for developing dietary deficiencies, one of which is vitamin B12.
Vitamin B12 is essential for the synthesis of normal DNA and healthy red and white blood cells. B12 is also necessary for helping to lower homocysteine levels – an often important marker of inflammation in the body.
According to the National Health and Medical Research Council (NHMRC), approximately two-thirds of people that follow a strict vegetarian diet have low vitamin B12 levels, and because it is found mainly in food from animal sources, it can be very tricky for vegans and strict vegetarians following a plant-only based diet, to obtain it from food alone. For these people, if their B12 levels are low, supplementation may be necessary.
The recommended daily intake (RDI) of vitamin B12 for adults aged 19 years and over is 2.4mcg (micrograms). To help put this into perspective, the average B12 content of a 100g sirloin steak is 1.4mcg, and, because plants do not naturally contain B12, the average content of a green leafy vegetable or lentil for example, is virtually zero.
Some plant foods, including spirulina, miso and tempeh, were once considered to be vegan sources of vitamin B12. However, it is now known that this is not the case; vitamin B12 is produced by bacteria in the large intestines of animals, which is why it is then found in animal-based food sources. Plants do not have the same bacterial process, or large intestines, and so cannot manufacture their own B12.
It is thought that any B12 that is found in plant foods may have actually occurred via bacterial contamination and may even be an inactive form, which the body cannot utilise. Thus, food that is fortified with B12 – such as soy milk and soy yoghurt, or meat substitutes/analogues, may be a good option for vegans and strict vegetarians.
If you are vegan or a vegetarian that does not consume eggs or dairy products, or you are concerned about your vitamin B12 intake, your doctor can test your B12 levels. Alternatively, you may wish to consider whether vitamin B12 supplementation is right for you.