Plant-Based Diet: Vitamin B12 Sources

Plant-based diets have increased considerably around the world in the last few years. While consuming a plant-based diet has been linked to health benefits, it is important to be aware of potential nutritional deficits which could lead to health conditions. Learn why vitamin B12 is so important, and how to get enough of it on a plant-based diet.

What is vitamin B12 and why is it so important?

Vitamin B12 is an essential micronutrient. We must obtain it from our diet because we cannot autonomously produce B12 in our body without consuming it from an external source. No animal can live without vitamin B12, and B12 shortages can have serious consequences in humans.

B12 is essential for the synthesis of DNA, the lack of B12 can damage the nervous system and cause cognitive issues like confusion, poor memory and, in more severe cases, dementia.^1,2,3,4 While there is a lag time before the B12 deficiency symptoms appear, the neurological and psychological consequences can become irreversible.^1,2

Vitamin B12 deficiency in plant-based diets

While plant-based diets have been linked to lower prevalence of diabetes, obesity, cancer and other cardiovascular diseases, several studies have shown that vitamin B12 is a common deficiency among those following a plant-based diet.^1,2,3,4

So why is there a higher risk of vitamin B12 deficiency when following a plant-based diet? There is a straightforward answer: This vitamin is only naturally available in animal-derived foods or products. Though, it may be interesting to point out that vitamin B12 is produced by bacteria and archaeon - not animals.

How B12 is naturally produced

Animals acquire vitamin B12 through the microbial interaction in their stomachs. Animal stomachs contain various microorganisms, including B12-synthesizing bacteria. The B12 produced is absorbed in the intestine and stored in the liver and muscles of the animals or secreted into their milk. Other animals may also pass B12 to their eggs, making meat, milk, and eggs good sources of vitamin B12.⁵

In aquatic environments, most phytoplankton also acquire vitamin B12 through interactions with bacteria. Phytoplankton are then eaten by fish and bivalves, making fish and shellfish other sources of B12.⁵ Additionally, livestock are often supplemented with vitamin B12 in their feed to boost the B12 content of animal products. 

How to get enough B12 on a plant-based diet

Vegetarians who eat milk and eggs have less chance of becoming B12 deficient. As milk and eggs are sources of this vitamin, they should increase the amount of these foods in their diet to avoid a shortfall. One cup of milk - or two eggs - provides about half of an adult's daily B12 recommendation.⁷

For plant-based eaters, there are some tricks that can be followed to lower or stop the risk of becoming B12 deficient:

1. Consume more plant-based foods fortified with B12, like breakfast cereals and plant-based drinks.

However, there is no scientific evidence that fortification on its own is enough to meet your daily needs. Several studies have shown that the risk of deficiency is higher for plant-based eaters who don’t take B12 supplements.² Therefore, vitamin B12 supplements are helpful in avoiding deficiencies and their health consequences.

2. Take B12 Supplements

There are many types of supplements such as multivitamins, sublingual forms (which are dissolved under the tongue), or even prescribed B12 shots in extreme circumstances, though this is usually used as a treatment for B12 shortage rather than a preventive method. Additionally, B12 supplements are also available as a prescription medication in a nasal gel form that is sprayed into the nose.⁶

While vitamin B12 is one of the most critical deficiencies, there are other vitamins and mineral deficiencies to be aware of when following a plant-based diet, including vitamin D, iron, zinc and omega-3 fatty acids.¹ So, if you’re vegan or vegetarian, it’s recommended that you plan your diet accordingly to include all the necessary nutrients to avoid any deficiencies and their associated risks.