Eating a plant-based diet is one of the most healthful actions you can take, but it carries the very serious and potentially fatal risk of vitamin B12 deficiency. Although plant-based diets are full of other vitamins and minerals, they are generally devoid of vitamin B12.
What is vitamin B12 and what does it do?
Vitamin B12 is a nutrient that helps keep the body’s nerve and blood cells healthy and helps make DNA, the genetic material in all cells. Vitamin B12 also helps prevent a type of anemia called megaloblastic anemia that makes people tired and weak.
Two steps are required for the body to absorb vitamin B12 from food. First, hydrochloric acid in the stomach separates vitamin B12 from the protein to which vitamin B12 is attached in food. After this, vitamin B12 combines with a protein made by the stomach called intrinsic factor and is absorbed by the body. Some people have pernicious anemia, a condition in which they cannot make intrinsic factor. As a result, they have trouble absorbing vitamin B12 from all foods and dietary supplements.
Vitamin B12 – Prevent Deficiency – Micronutrients on a Vegan Diet
Vitamin B12, or cobalamin, is naturally found in animal foods or bacteria. Animals obtain vitamin B12 by eating foods that are covered in bacteria or from the bacteria that already line their own guts. Humans have lots of bacteria in their guts, but only in the colon. Unfortunately, humans are unable to absorb the vitamin B12 produced in the colon because vitamin B12 is only absorbed in the small intestine, which is upstream of the colon.
Intake recommendations for vitamin B12 and other nutrients are provided in the Dietary Reference Intakes (DRIs) developed by the Food and Nutrition Board (FNB) at the Institute of Medicine (IOM) of the National Academies (formerly National Academy of Sciences) . DRI is the general term for a set of reference values used for planning and assessing nutrient intakes of healthy people. These values, which vary by age and gender , include:
- Recommended Dietary Allowance (RDA): Average daily level of intake sufficient to meet the nutrient requirements of nearly all (97%–98%) healthy individuals; often used to plan nutritionally adequate diets for individuals.
- Adequate Intake (AI): Intake at this level is assumed to ensure nutritional adequacy; established when evidence is insufficient to develop an RDA.
- Estimated Average Requirement (EAR): Average daily level of intake estimated to meet the requirements of 50% of healthy individuals; usually used to assess the nutrient intakes of groups of people and to plan nutritionally adequate diets for them; can also be used to assess the nutrient intakes of individuals.
- Tolerable Upper Intake Level (UL): Maximum daily intake unlikely to cause adverse health effects.
Table 1 lists the current RDAs for vitamin B12 in micrograms (mcg) . For infants aged 0 to 12 months, the FNB established an AI for vitamin B12 that is equivalent to the mean intake of vitamin B12 in healthy, breastfed infants.
|0–6 months*||0.4 mcg||0.4 mcg|
|7–12 months*||0.5 mcg||0.5 mcg|
|1–3 years||0.9 mcg||0.9 mcg|
|4–8 years||1.2 mcg||1.2 mcg|
|9–13 years||1.8 mcg||1.8 mcg|
|14+ years||2.4 mcg||2.4 mcg||2.6 mcg||2.8 mcg|
* Adequate Intake
Sources of Vitamin B12
Vitamin B12 is naturally found in animal products, including fish, meat, poultry, eggs, milk, and milk products. Vitamin B12 is generally not present in plant foods, but fortified breakfast cereals are a readily available source of vitamin B12 with high bioavailability for vegetarians [5,13-15]. Some nutritional yeast products also contain vitamin B12. Fortified foods vary in formulation, so it is important to read the Nutrition Facts labels on food products to determine the types and amounts of added nutrients they contain.
Several food sources of vitamin B12 are listed in Table 2.
Table 2: Selected Food Sources of Vitamin B12 
|Clams, cooked, 3 ounces||84.1||1,402|
|Liver, beef, cooked, 3 ounces||70.7||1,178|
|Nutritional yeasts, fortified with 100% of the DV for vitamin B12, 1 serving||6.0||100|
|Trout, rainbow, wild, cooked, 3 ounces||5.4||90|
|Salmon, sockeye, cooked, 3 ounces||4.8||80|
|Trout, rainbow, farmed, cooked, 3 ounces||3.5||58|
|Tuna fish, light, canned in water, 3 ounces||2.5||42|
|Cheeseburger, double patty and bun, 1 sandwich||2.1||35|
|Haddock, cooked, 3 ounces||1.8||30|
|Breakfast cereals, fortified with 25% of the DV for vitamin B12, 1 serving||1.5||25|
|Beef, top sirloin, broiled, 3 ounces||1.4||23|
|Milk, low-fat, 1 cup||1.2||18|
|Yogurt, fruit, low-fat, 8 ounces||1.1||18|
|Cheese, Swiss, 1 ounce||0.9||15|
|Beef taco, 1 soft taco||0.9||15|
|Ham, cured, roasted, 3 ounces||0.6||10|
|Egg, whole, hard boiled, 1 large||0.6||10|
|Chicken, breast meat, roasted, 3 ounces||0.3||5|
*DV = Daily Value. The U.S. Food and Drug Administration (FDA) developed DVs to help consumers compare the nutrient contents of products within the context of a total diet. The DV for vitamin B12 used for the values in Table 2 is 6.0 mcg for adults and children age 4 years and older . This DV, however, is changing to 2.4 mcg as the updated Nutrition and Supplement Facts labels are implemented . The updated labels and DVs must appear on food products and dietary supplements beginning in January 2020, but they can be used now . FDA does not require food labels to list vitamin B12 content unless a food has been fortified with this nutrient. Foods providing 20% or more of the DV are considered to be high sources of a nutrient, but foods providing lower percentages of the DV also contribute to a healthful diet.
B12 deficiency 👉 Warning Signs & Symptoms of Vitamin B12 Deficiency
Groups at Risk of Vitamin B12 Deficiency
The main causes of vitamin B12 deficiency include vitamin B12 malabsorption from food, pernicious anemia, postsurgical malabsorption, and dietary deficiency . However, in many cases, the cause of vitamin B12 deficiency is unknown. The following groups are among those most likely to be vitamin B12 deficient.
Atrophic gastritis, a condition affecting 10%–30% of older adults, decreases secretion of hydrochloric acid in the stomach, resulting in decreased absorption of vitamin B12 [5,11,35-39]. Decreased hydrochloric acid levels might also increase the growth of normal intestinal bacteria that use vitamin B12, further reducing the amount of vitamin B12 available to the body .
Individuals with atrophic gastritis are unable to absorb the vitamin B12 that is naturally present in food. Most, however, can absorb the synthetic vitamin B12 added to fortified foods and dietary supplements. As a result, the IOM recommends that adults older than 50 years obtain most of their vitamin B12 from vitamin supplements or fortified foods . However, some elderly patients with atrophic gastritis require doses much higher than the RDA to avoid subclinical deficiency .
Individuals with pernicious anemia
Pernicious anemia, a condition that affects 1%–2% of older adults , is characterized by a lack of intrinsic factor. Individuals with pernicious anemia cannot properly absorb vitamin B12 in the gastrointestinal tract [3,5,9,10]. Pernicious anemia is usually treated with intramuscular vitamin B12. However, approximately 1% of oral vitamin B12 can be absorbed passively in the absence of intrinsic factor , suggesting that high oral doses of vitamin B12 might also be an effective treatment.
Individuals with gastrointestinal disorders
Individuals with stomach and small intestine disorders, such as celiac disease and Crohn’s disease, may be unable to absorb enough vitamin B12 from food to maintain healthy body stores [12,26]. Subtly reduced cognitive function resulting from early vitamin B12 deficiency might be the only initial symptom of these intestinal disorders, followed by megaloblastic anemia and dementia.
Individuals who have had gastrointestinal surgery
Surgical procedures in the gastrointestinal tract, such as weight loss surgery or surgery to remove all or part of the stomach, often result in a loss of cells that secrete hydrochloric acid and intrinsic factor [5,42,43]. This reduces the amount of vitamin B12, particularly food-bound vitamin B12 , that the body releases and absorbs. Surgical removal of the distal ileum also can result in the inability to absorb vitamin B12. Individuals undergoing these surgical procedures should be monitored preoperatively and postoperatively for several nutrient deficiencies, including vitamin B12 deficiency .
Strict vegetarians and vegans are at greater risk than lacto-ovo vegetarians and nonvegetarians of developing vitamin B12 deficiency because natural food sources of vitamin B12 are limited to animal foods . Fortified breakfast cereals and fortified nutritional yeasts are some of the only sources of vitamin B12 from plants and can be used as dietary sources of vitamin B12 for strict vegetarians and vegans. Fortified foods vary in formulation, so it is important to read the Nutrition Facts labels on food products to determine the types and amounts of added nutrients they contain.
Pregnant and lactating women who follow strict vegetarian diets and their infants
Vitamin B12 crosses the placenta during pregnancy and is present in breast milk. Exclusively breastfed infants of women who consume no animal products may have very limited reserves of vitamin B12 and can develop vitamin B12 deficiency within months of birth [5,46]. Undetected and untreated vitamin B12 deficiency in infants can result in severe and permanent neurological damage.
The American Dietetic Association recommends supplemental vitamin B12 for vegans and lacto-ovo vegetarians during both pregnancy and lactation to ensure that enough vitamin B12 is transferred to the fetus and infant . Pregnant and lactating women who follow strict vegetarian or vegan diets should consult with a pediatrician regarding vitamin B12 supplements for their infants and children .FINAL WARNING! Try THIS and You Might Never See a Doctor Again! (Must See Doctor Video)
What is VeganSafe Vitamin B-12?
VeganSafe B-12 is a certified organic, vegan formula that contains methylcobalamin and adenosylcobalamin, the two most bioactive forms of B-12. Although most of us simply know vitamin B-12 as the B vitamin responsible for energy production, it’s important to understand that “vitamin B-12” is actually a catch-all term for a class of vitamins known as cobalamins — and they’re not equal in their benefits.