Vitamin B12 is an essential water soluble vitamin that is specifically important for the myelination of nerves and function of the central nervous system, formation of red blood cells, and DNA synthesis. It is found naturally in animal foods such as red meat, fish, poultry, eggs, and dairy products.
Health Benefits of Vitamin B12
- Supports healthy red blood cell production
- Maintains healthy nerve function
- Helps produce DNA
- Supports normal brain function
- Helps convert homocysteine into methionine
- Supports normal energy metabolism
- Helps prevent megaloblastic anemia
Since plants do not naturally contain vitamin B12, vegetarians and vegans often rely on fortified foods, such as nutritional yeast, breakfast cereals, and plant-based milks, or a vitamin B12 supplement to meet their daily needs.
People following a vegan diet are at the highest risk of vitamin B12 deficiency if they do not consume fortified foods or supplements. However, vitamin B12 deficiency can also occur in people who eat animal foods if they have difficulty absorbing it.
Although vitamin B12 is found naturally in animal foods, getting enough in your diet is only part of the equation. Your body also needs to absorb it properly. Specialized cells in your stomach, called parietal cells, produce both stomach acid and intrinsic factor, a protein that is essential for vitamin B12 absorption.
Stomach acid helps release vitamin B12 from the proteins in food, while intrinsic factor binds to vitamin B12 and carries it to the last part of the small intestine (the terminal ileum), where it is absorbed. If your stomach doesn’t produce enough acid or intrinsic factor, or if your small intestine isn’t functioning properly, you may develop a vitamin B12 deficiency even if you’re eating enough vitamin B12-rich foods.
People are more likely to develop a vitamin B12 deficiency if they:
- Follow a vegetarian or vegan diet without adequate vitamin B12 supplementation
- Have low stomach acid
- Have pernicious anemia
- Take acid-reducing medications, such as proton pump inhibitors, long-term
- Have had bariatric surgery
- Have had part or all of their stomach removed (gastrectomy)
- Have celiac disease
- Have Crohn’s disease or other inflammatory bowel diseases affecting the small intestine
- Have small intestinal bacterial overgrowth (SIBO)
- Have pancreatic insufficiency
- Are older adults, as stomach acid production naturally declines with age
Pernicious Anemia and Vitamin B12
Pernicious anemia is an autoimmune condition that prevents your body from properly absorbing vitamin B12. It occurs when the immune system attacks the parietal cells of the stomach that produce intrinsic factor. Without enough intrinsic factor, vitamin B12 cannot be absorbed efficiently, even if you’re eating plenty of vitamin B12-rich foods.
Because pernicious anemia causes a permanent loss of intrinsic factor, most people require lifelong vitamin B12 supplementation to prevent vitamin B12 deficiency.
A vitamin B12 deficiency can affect many different systems throughout the body, resulting in a wide range of symptoms. Because vitamin B12 is essential for red blood cell production, nervous system function, and DNA synthesis, low levels can lead to fatigue, neurological symptoms, and anemia.
Common Signs and Symptoms of a Vitamin B12 Deficiency Include:
- Fatigue and low energy
- Weakness
- Pale skin
- Jaundice (yellowing of the skin or eyes)
- Megaloblastic (macrocytic) anemia
- Headaches
- Heart palpitations
- A swollen, smooth, or sore tongue (glossitis)
- Diarrhea
- Numbness or tingling in the hands and feet (peripheral neuropathy)
- Poor balance
- Brain fog or difficulty concentrating
- Memory problems or dementia in severe cases
- Mood changes or other neuropsychiatric symptoms
- Low counts of white and red blood cells
Vitamin B12 and the Nervous System
Vitamin B12 plays an important role in keeping your nervous system healthy. Research suggests that it helps protect nerve cells, supports the maintenance of the myelin sheath (the protective coating that surrounds your nerves), and may also help support remyelination, the process of repairing damaged myelin after nerve injury.
Animal studies have found that vitamin B12 can promote the growth of new nerve fibers, increase myelin thickness, and improve nerve function following injury. While more human research is needed, these findings highlight vitamin B12 as an essential nutrient for maintaining healthy nerves and supporting normal nervous system function.
Vitamin B12 and Methylation
Vitamin B12 is an essential nutrient for the methylation pathway because it acts as a cofactor for the enzyme methionine synthase. This enzyme helps convert homocysteine into methionine, which is then used to produce S-adenosylmethionine (SAMe), the body’s primary methyl donor.
SAMe is the body’s primary methyl donor, supplying methyl groups for hundreds of important methylation reactions throughout the body. These reactions support many essential processes, including:
- Healthy brain and nervous system function
- Neurotransmitter production and metabolism
- One of the liver’s Phase II detoxification pathways (methylation)
- Gene regulation (DNA methylation)
- Creatine production to support energy production in muscles and the brain
- Phospholipid production to help maintain healthy cell membranes and myelin
- Histamine metabolism
Because vitamin B12 is required to produce SAMe, a deficiency may impair many methylation reactions throughout the body. As a result, maintaining adequate vitamin B12 levels is important for healthy brain function, nervous system health, DNA synthesis, and many other processes throughout the body.
Foods High in Vitamin B12
Vitamin B12 is found naturally almost exclusively in animal foods. Some of the best dietary sources include:
- Beef liver
- Clams, mussels, and oysters
- Fish
- Beef and lamb
- Chicken and turkey
- Milk and yogurt
- Cheese
- Eggs
Vegan Sources of Vitamin B12
Because vitamin B12 is not naturally abundant in plant foods, vegans should rely on fortified foods or supplements to meet their daily needs. Good vegan sources include:
- Fortified breakfast cereals
- Fortified plant milks
- Fortified nutritional yeast
- Fortified yeast extracts (such as Marmite, which is fortified)
- Dried nori (purple laver)
- Vitamin B12 supplements
How Much Vitamin B12 Do You Need?
The amount of vitamin B12 you need each day depends on your age. The recommended daily intake is:
| Age Group | Recommended Daily Intake |
| Children (1–13 years) | 0.9–1.8 mcg |
| Adults (14 years and older) | 2.4 mcg |
Pregnancy and breastfeeding: Vitamin B12 requirements increase during pregnancy (2.6 mcg/day) and breastfeeding (2.8 mcg/day). Vitamin B12 plays an essential role in your baby’s brain and nervous system development, so getting enough is particularly important during these life stages.
Supplementing with Vitamin B12
Supplementing with vitamin B12 is a good idea if you have signs of vitamin B12 deficiency or malabsorption issues, or if you eat a vegan diet. A serum vitamin B12 level below 200 pg/mL (148 pmol/L) is generally considered a vitamin B12 deficiency.
When vitamin B12 levels become too low, your body may not be able to produce healthy red blood cells or maintain normal nerve function. Vitamin B12 deficiency can also cause homocysteine and methylmalonic acid (MMA) levels to rise, which are common markers used to help diagnose vitamin B12 deficiency.
A 2024 review of 13 studies involving over 4,200 people found that oral, sublingual, and vitamin B12 injections were all effective for treating vitamin B12 deficiency. Injections slightly increased blood vitamin B12 levels more than the other methods; however the difference was not considered clinically significant, meaning all three options can be effective for most people.
Another 2024 study found that taking 1,000 mcg of oral vitamin B12 daily effectively treated vitamin B12 deficiency in people with pernicious anemia. Nearly 89% were no longer deficient after one month, and all participants maintained healthy vitamin B12 levels throughout the one-year study, suggesting that high-dose oral supplements are effective for people with pernicious anemia.
Types of Vitamin B12 Supplements
Vitamin B12 supplements come in several different forms. All can help treat or prevent vitamin B12 deficiency, but some are more bioavailable.
- Methylcobalamin – The active, bioavailable form of vitamin B12 that is directly used by the body. It is commonly found in high-quality supplements.
- Hydroxocobalamin – A naturally occurring form that stays in the body longer than some other forms. It is commonly used in vitamin B12 injections and can also be found in supplements.
- Cyanocobalamin – The most widely studied and commonly used form of vitamin B12. It is stable and inexpensive, but it needs to be converted into active forms of vitamin B12 after absorption.
- Adenosylcobalamin – Another active form of vitamin B12 that is primarily involved in energy production within the mitochondria.
Best Recipes High in Vitamin B12
If you’re looking for delicious ways to increase your vitamin B12 intake, try incorporating these vitamin B12-rich recipes into your diet . My Blueberry Yogurt Chia Pudding is made with yogurt, a natural source of vitamin B12, while my Low FODMAP Quiche provides vitamin B12 from both eggs and dairy. For a savory option, my Low FODMAP Chicken Rice Soup contains chicken, another excellent source of vitamin B12.
If you follow a vegan diet, my Glory Bowl Dressing is made with fortified nutritional yeast, making it a great plant-based source of vitamin B12.
Including these foods regularly can help you meet your daily vitamin B12 needs as part of a healthy, balanced diet. If you don’t consume many animal products, taking a vitamin B12 supplement is a great way to prevent a deficiency and all the symptoms associated with low B12.
References:
Oral vitamin B12 supplementation in pernicious anemia: a prospective cohort study – PubMed
Vitamin B12-Containing Plant Food Sources for Vegetarians – PMC
Vitamin B12 sources and bioavailability – PubMed
https://onlinelibrary.wiley.com/doi/10.1155/2021/9968228
Leave a Reply