What is the importance of vitamin B12 supplementation in plant-based diets?

By Dr. Sanchari Sinha Dutta, Ph.D.Reviewed by Benedette Cuffari, M.Sc.Dec 9 2022

A recent article published in the European Journal of Nutrition highlights the importance of vitamin B12 supplementation for individuals consuming a plant-based or vegan diet, as a high prevalence of vitamin B12 deficiency has been observed in this population.

Study: The importance of vitamin B12 for individuals choosing plant‑based diets. Image Credit: concept w/Shutterstock

Background

The popularity of a sustainable diet is increasing exponentially in the Western world. A sustainable diet involves a greater consumption of plant-based foods and minimal or no intake of animal-based foods.

This type of diet has positive environmental and ethical impacts due to the significant reduction in animal sacrifice. However, vitamin B12 deficiency is a major drawback of following plant-based or vegan diets, as plants alone cannot provide an adequate amount of this essential nutrient.

Recent estimates indicate that the average daily intake of vitamin B12 is 7.2 µg in meat eaters compared to vegans who receive only 0.4 µg of vitamin B12 from their diet. This can significantly increase the risk of vitamin B12 deficiency.

The vegan diet is the most restricted form of a plant-based diet, as it limits the intake of all animal foods, including meat, egg, fish, milk, and milk products. Other kinds of plant-based diets are less stringent and allow for the occasional intake of certain types of animal-based foods. Importantly, unfortified plant-based foods cannot meet daily vitamin B12 requirements.

Plant-based diet and vitamin B12 deficiency  

A nutritional survey conducted in the United Kingdom in 2018 identified 3% of the participants as vegetarians and 1% as vegans.

According to statements provided by various nutrition and dietetics societies throughout the world, appropriately planned plant-based diets are healthy in terms of reducing obesity, diabetes, and other chronic diseases. These diets are considered appropriate for all stages of life, including pregnancy, lactation, infancy, childhood, adolescence, older adulthood, and for athletes.

However, in all statements, vegans have been advised to ensure adequate supplementation of vitamin B12 to avoid its deficiency.

Health impact of a vegan diet

Vegetarian and vegan diets are gaining widespread popularity because of their potential health benefits due to their anti-inflammatory, antioxidant, anticancer, lipid-lowering, immunomodulatory, and metabolic effects. However, several studies have suggested that consuming un-supplemented plant-based foods can lead to a severe deficiency of many micronutrients, including vitamin B12, iron, calcium, iodine, and selenium.

Vitamin B12 is of particular concern because plants cannot synthesize this essential nutrient. A substantial portion of animal-based foods is required to avoid vitamin B12 deficiency. Previous studies have shown that individuals following a vegetarian or vegan diet since birth have higher levels of vitamin B12 deficiency than those who adopt these diets later in life.    

Vitamin B12 is vital for many metabolic activities and is essential for the synthesis of blood cells and brain tissues. Several studies have reported associations between vegan or vegetarian diets and an increased risk of neurological and neuropsychiatric disorders. A higher risk of bone fractures has also been observed in individuals following strict vegan diets.

Health effects of vitamin B12 deficiency

The most common signs and symptoms of vitamin B12 deficiency include cognitive deficits, depression, dyspnea, loss of postural hypotension, muscle weakness, as well as mental and physical fatigue. However, an accurate interpretation of symptoms is often difficult because vitamin B12 deficiency can occur without blood levels being below the clinical cutoff for deficiency.

During pregnancy, a vitamin B12 deficiency can lead to serious complications, including spontaneous abortion, preeclampsia, low birth weight, and fetal developmental disorders. This essential nutrient is particularly vital for neural myelination, neurological and cognitive development, and growth in infants.

Current recommendations for vitamin B12

In the U.K., the recommended daily intake of vitamin B12 is 1.5 µg. Comparatively, in the United States, the value is 2.4 µg/day for adults and 2.6-2.8 µg/day for pregnant and lactating women. Within the European Union, the value is 4 µg/day for adults and 4.5-5 µg/day for pregnant and lactating women. These estimates indicate that the current U.K. recommendation for vitamin B12 is inadequate and incomplete.

The daily requirement of vitamin B12 increases with aging, pregnancy, chronic diseases, and the use of certain medications. Thus, an intake of 4-20 µg/day is more appropriate for avoiding vitamin B12 deficiency.

To ensure adequate vitamin B12 intake, the British Dietetic Association advises that vegans consume certified vitamin B12 supplements and fortified foods. These individuals should also seek advice from experts to properly plan their plant-based diet.