Vitamin B12 is a unique vitamin in so many ways. It is the only vitamin that contains cobalt, an essential trace mineral. You only need vitamin B12 in small amounts – less amounts that any other vitamin – but eating lots of fresh foods and vegetable doesn’t really help in getting your daily dose, as this vitamin is only found in animal-based products such as eggs, dairy products, meat and fish.
Vitamin B12 is an extremely crucial vitamin and its deficiency can have far reaching consequences for your health, including irreversible damage to your nervous system in the case of severe deficiency in the long-term.
In this article, we will discuss the best food sources of vitamin B12 and why supplementation may sometimes be necessary.
Role of Vitamin B12
Vitamin B12 has many important functions the body. It is required for:
- Formation of healthy, mature red blood cells
- Energy production (vitamin B12 is involved in the metabolism of fat, protein and carbohydrate).
- DNA synthesis
- Healthy nervous system and brain function
- Removing homocysteine from the blood (homocysteine is a protein that is known to damage your arteries and is linked with heart disease).
- Regeneration of folic acid
Vitamin B12 is only found in animal-based products. Plant sourced foods don’t contain this essential vitamin. Some varieties of seaweeds such as nori (the Japanese name for edible seaweed) also contains B12, but not enough to meet your daily requirements.
However, what is interesting is that animals don’t make their own vitamin B12. It is, in fact, produced by microorganisms found in their gastrointestinal tract. The bacteria present in your gut can also make vitamin B12, but experts claim that this vitamin is not highly usable by the body.
Here is a list of food sources of vitamin B12:
- Organ meats like liver and kidneys
- Fish like salmon and trout
- Milk and dairy products
- Fortified nutritional yeast
- Fortified cereals
Do you eat a lot of meat, eggs, fish and dairy products? These foods provide good amounts of vitamin B12. But you may not be getting enough from your diet. It is because vitamin B12 is not easily absorbed by the body. It undergoes a lot of steps before it is eventually absorbed, and issues with any of these steps would adversely affect its metabolism.
Let’s look at important milestones in B12 absorption:
- In foods that contain vitamin B12, the vitamin is not present in free form. It is bound to proteins.
- During digestion, acid and pepsin (an enzyme) in the stomach break-down these proteins, releasing the vitamin B12.
- The released vitamin B12 now binds to intrinsic factor (IF), a special transport protein produced by the stomach.
- The small intestine has receptors for intrinsic factor. These receptors bind to the IF-B12 complex, resulting in vitamin B12 absorption.
Intrinsic factor can only bind to receptors in the small intestine when you have healthy levels of calcium. When you have calcium deficiency, your body won’t be able to absorb vitamin B12.
Research show that long-term use of metformin, a drug used to treat diabetes, can cause vitamin B12 deficiency. It is because metformin reduces the levels of calcium in the intestine. Metformin is also the most commonly used drug to treat women with polycystic ovary syndrome (PCOS).
A 2016 study published in the Journal of Clinical Endocrinology and Metabolism found that long-term use of metformin can cause B12 deficiency and anemia. It also recommends health practitioners to perform routine tests of B12 levels in patients using metformin drug. 
Taking Vitamin B12 and calcium together may offset the vitamin B12 deficiency caused by metformin.
Are you at risk of vitamin B12 deficiency?
Age, some health conditions and certain medications weaken your body’s ability to make sufficient amounts of acid, intrinsic factor and enzymes involved in healthy and efficient absorption. This results in poor absorption of vitamin B12 – leading to deficiency. Here is a short list of what affects your bodies ability to absorb Vitamin B12:
- Atrophic gastritis, thinning of the stomach lining. This condition reduces the secretion of intrinsic factor
- Long term use of drugs used to treat gastroesophageal reflux disease (GERD) and peptic ulcers. These include H2 blockers and proton pump inhibitors.
- Pernicious anemia (it is an autoimmune disorder wherein your immune system kills cells that produce intrinsic factor).
- Weight loss surgery and surgery that removes parts of stomach or small intestine
- Conditions such as Crohn's disease, colitis, celiac disease, leaky gut and bacterial overgrowth
- Conditions such as diabetes
- Pancreatic disorders
- MTHFR gene mutations
- Excessive consumption of alcohol. This not only inflames the stomach lining and affects the production of intrinsic factor, but also damages the liver. This is important because most of the vitamin B12 is stored in the liver.
- Autoimmune disorders such as hyperthyroidism or lupus
- Long-term use of laxatives
Vitamin B12 deficiency can take some time to develop. It is because unlike most vitamins, your body can store vitamin B12 for 3-5 years. If the deficiency is not diagnosed and rectified in time, it can lead to permanent damage.
The following symptoms indicate that you have B12 deficiency:
- Persistent weakness and fatigue
- Neurological disorders ranging from numbness and tingling in hands and feet, poor memory, confusion, brain fog, depression, paranoia, behavior changes, headaches and trouble maintaining balance
- Gastrointestinal problems including constipation or diarrhea
- Loss of appetite
- Red and swollen tongue
- Sore mouth
- Pale skin
- Reduced reflexes
- Dementia and schizophrenia like symptoms
Most of you are already aware that folic acid is important for healthy development of your baby. Most women trying to conceive or those in early pregnancy take folic acid to prevent the risk of neural tube defects such as spina bifida, a condition where a baby’s spine is not properly developed. But not many people know that you also need vitamin B12 to prevent neural tube and other neurological defects in babies.
Vitamin B12 deficiency in pregnancy is also associated with premature delivery. This 2017 study found that “lower maternal B12 levels are associated with a higher risk of preterm birth and that the risk of preterm birth is particularly high in the presence of B12 deficiency during pregnancy.” 
Low levels of Vitamin B12 in pregnant women can also cause low levels of B12 in their new born. Infants exclusively breastfed by mothers who are strictly vegetarian or have undiagnosed pernicious anemia are also likely to be deficient. This can result in vomiting, failure to thrive, abnormal movements and delayed development in infants.
Taking vitamin B12 supplements
Vitamin B12 supplements can help those at a high risk of vitamin B12 deficiency. All vegans must take B12 fortified foods and B12 supplements to make sure they have healthy levels of B12 as they may otherwise not be getting enough. Pregnant and breastfeeding women must also take B12 supplements to avoid deficiency in their infants and support their growth and development.
In foods, vitamin B12 is bound to proteins and must be released. You need healthy production of gastric acid and enzymes to free B12. But in supplements, vitamin B12 is already available in free form. For this reason, older people and those taking metformin and other drugs that reduce gastric acid can benefit from taking vitamin B12 supplements.
People with pernicious anemia
In pernicious anemia, your body is not able to make intrinsic factor required for optimum B12 absorption. B12 enriched foods and supplements are not effective for people affected by this condition. People with celiac disease or Crohn's disease may also have trouble absorbing vitamin B12 from oral supplements. Your doctor is likely to recommend muscular injection in such cases.
It is generally believed that intramuscular injections are better than oral supplements in boosting your levels. But this is not true. Oral B12 supplements are as effective in improving your vitamin B12 status as IM shots, except in certain conditions as discussed above. Liposomal supplements, in particular, are creating quite a buzz in this respect and offer a very good alternative method of supplementation.
Liposomal Vitamin B12 supplements bypass the gastrointestinal route and are directly delivered into the bloodstream, increasing absorption and bioavailability.
Vitamin B12 and folic acid
Vitamin B12 works very closely with folic acid to carry out its diverse roles. In addition, you need vitamin B12 to convert folic acid into a form that can be actively used by the body. The same goes for folic acid, as you won’t be able to process and utilize vitamin B12 if you don’t have folic acid in adequate amounts.
One of the frequently asked questions is: Are folic acid and folate two different things? They are the name of the same vitamin (B9). But folate occurs naturally in foods whereas folic acid is the synthetic version, that you get from supplements and fortified foods. Chickpeas, broccoli, leafy green vegetables and peas are some good sources of folate.
Taking more than 1 mg of folic acid a day can mask the symptoms induced by vitamin B12 deficiency. In that case, you won’t experience typical signs of B12 deficiency such as fatigue, but the basic shortage will still cause damage to the nervous system. It can even cause irreversible damage if an underlying deficiency is not identified and allowed to persist for a long time. It is better to take folic acid along with vitamin B12 but in right doses. It is even better to take B9 in folate form. Always consult your health care professional, especially if you are pregnant.
It is also a good opportunity to mention MTHFR Gene Mutations. Methylenetetrahydrofolate reductase (MTHFR) is a gene that tells the body to make an enzyme called methylenetetrahydrofolate reductase. This enzyme is involved in the processing of many amino acids.
The enzyme converts folate into its active, usable form that you need for methylation reactions, where methyl groups are added to proteins, enzymes, DNA and various neurotransmitters. These reactions take place in every cell of the body. (The duo of folic acid and vitamin B12 is supported by vitamin C in the metabolism of proteins). Any mutations in this gene cause excessive build-up of folate in a form that your body can’t use.
More specifically, both folate and vitamin B12 helps in converting toxic homocysteine into methionine, which plays an important role in methylation reactions. These reactions are critical for:
- Red blood cells formation, DNA synthesis and repair
- Regulating homocysteine levels
- Synthesis of glutathione, the master anti-oxidant that helps in detoxification
- Synthesis and regeneration of myelin sheath, a covering that protects nerves from damage.
- Production of important neurotransmitters such as norepinephrine, dopamine and serotonin. These hormones are involved in regulating mood and memory.
- Processing hormones such as estrogen
MTHFR gene mutations are also associated with many psychiatric disorders including depression, bipolar disorder and ADHD. It also increases one’s risk of heart disease, stroke, osteoporosis, certain forms of cancers and autoimmune disorders including thyroid disease.
Worried about taking too much vitamin B12?
There is no established upper limit on how much B12 you can safely consume. It is a pretty safe vitamin even at high doses. Vegans of any age, people above 50 years, pregnant and breastfeeding women, those with inflammatory bowel disease and intestinal surgeries and individuals taking antacids and metformin must immediately consult their health care professional to check their B12 status and supplement accordingly. And remember, if you have pernicious anemia or suffer from Crohn's and Celiac disease, you may benefit from intramuscular injections.
- Aroda et al. Long-term Metformin Use and Vitamin B12 Deficiency in the Diabetes Prevention Program Outcomes Study. J Clin Endocrinol Metab. 2016
- Rogne et al. Associations of Maternal Vitamin B12 Concentration in Pregnancy With the Risks of Preterm Birth and Low Birth Weight: A Systematic Review and Meta-Analysis of Individual Participant Data. American Journal of Epidemiology. 2017