Vitamin B12

What is it?

Vitamin B12 is a water-soluble vitamin that is found naturally in some foods, added to others, and available in both dietary supplements and pharmaceutical medications. Actually, it is only found naturally in foods of animal origin. It is also the largest and most complex of all the vitamins.

What other names is it known by?

B12 contains the cobalt mineral and therefore versions of this mineral’s name.

• Cobalamin

• Methylcobalamin

• Coenzyme B12

• Adenosylcobalamin

• 5-deoxyadenosylcobalamin

• Hydroxycobalamin

• Cyanocobalamin.

Methylcobalamin and 5-deoxyadenosylcobalamin are the metabolically active forms of B12. Hydroxycobalamin and cyanocobalamin can be converted to these forms, after which they become biologically active. When it is commercially produced it is usually from bacterial fermentation, and as the form cyanocobalamin.

What does it do?

Vitamin B12 has several important functions in the body. It is required for:

• the development, function, and myelination of the central nervous system

• the formation of healthy red blood cells

• DNA synthesis

• the release of energy from food (the metabolism of fat and carbohydrate)

• a few enzymatic reactions to be successful

• healthy growth.

To summarize some of the bullets above, B12 is necessary for something called one-carbon metabolism. Huh? One carbon metabolism is a group of biochemical reactions that occur within cells. These reactions are critical to maintain the health of cells. They break down different sources of carbons to create one-carbon (methyl) units that are utilized in fundamental reactions within cells. Because of the way these one-carbon units are produced and utilized, one-carbon metabolism serves as an integrative pathway through which cells are able to optimally respond to changes in both their intra- and extracellular conditions. Essentially one-carbon metabolism serves as an integrator of the nutritional status of cells. In addition, one-carbon metabolism is critical for the production of DNA, amino acid balance, epigenetic maintenance, and antioxidant defenses. One-carbon metabolism is essential for the normal healthy functioning of cells, and the immune system. Improper one-carbon metabolism has been implicated in many different diseases, cancer being one that is commonly studied.

One-carbon metabolism is driven by folate, and something called the methionine cycle. B12, among other nutrients, plays a critical role in the reactions that allow one-carbon metabolism to occur. Therefore, B12 deficiency can have severe detrimental effects on overall health. Not to cause confusion, but likewise, an excess of B12 has also been linked to the development of various cancers and all-cause mortality. Why? Because just like B12 deficiency interrupts the one-carbon metabolism pathway, an excess can put it into overdrive, essentially increasing DNA synthesis to the benefit of rapidly dividing cells.

In gut health, B12 plays an important role in maintaining the health of the gut microbiome. By helping to enhance good gut bacteria, it plays an important role in shaping both local gut immunity, and total immunity. B12 deficiency may contribute to dysbiosis in the gut, or the reduction of good bacteria, and over proliferation of bad bacteria. Research into the gut-brain axis has actually linked B12 deficiency associated with the gut to stroke.

Where does it come from?

In food form, vitamin B12 is bound to protein and must be released in order for it to be absorbed. This process starts in the mouth with saliva and continues in the stomach with hydrochloric acid and gastric protease. It is in its freed form in the first part of the small intestine, and then absorbed in the last part in the presence of intrinsic factor. Vitamin B12 that is added to foods and dietary supplements is already in the freed form and doesn’t need to go through these extra steps.

B12 can also be found in a variety of fortified foods, beverages (energy drinks), and dietary supplements. In fact, many fortified foods, beverages, and dietary supplements often provide well above the recommended dietary intake of B12, therefore many individuals are getting way too much vitamin B12 in their diets.

How much is needed?

In the US, the RDA is as follows:

*Adequate intake

It’s important to note that deficiency of B12 can exist and is often seen in 10-15% of individuals over the age of 60. Signs of deficiency may include neuropathy, megaloblastic anemia, memory impairment, numbness, tingling, breathlessness, osteoporosis, and cardiovascular disease, among others.

Groups at risk of B12 deficiency include vegetarians, elderly, alcoholics, those with pernicious anemia, gastric atrophy, food-bound vitamin B12 malabsorption, gastrectomy, bacterial overgrowth, small intestine defects, pancreatic insufficiency, AIDs, vitamin B6 deficiency, and those who take the following pharmaceuticals (antibiotics, anti-diabetics, anti-epileptic drugs, anti-gout medications, antacids, oral contraceptives, anticonvulsants, and tuberculosis meds).

There seems to be no immediate and outward signs of consuming too much B12, however too much B12 may contribute to an uninvited alteration in one-carbon metabolism, which may cause a whole host of other issues.

Either way, vitamin B12 can be measured through a simple blood test. While it may not be routine it is something a doctor can order to check overall status.

How do I get it?

If you’re taking a vitamin B12 supplement, and eating fortified foods, you may not need any extra from your diet. However, we usually recommend that you get whatever you need from natural, non-fortified sources, before you consume anything fortified, or dietary supplements. That is, unless you have a condition that requires you to consume more, or inhibits absorption. Either way, the below are some ideas on how you can get vitamin B12 in your diet. These are not complete meals, just examples of what you could add into your daily routine at each meal.

Breakfast: 6 oz of plain fat-free yogurt, boiled egg = 1.5 mcg

Lunch: roasted turkey breast sandwich (3 oz meat) = 0.3 mcg

Dinner: 3 oz Atlantic salmon = 2.6 mcg

Total: 4.4 mcg (for an adult this is 2 mcg above what is recommended)

If this was your day of eating, then you would most definitely not need to eat any fortified foods or take any B12 supplements!

References

Brescoll, J., & Daveluy, S. (2015). A review of vitamin B12 in dermatology. Am J Clin Dermatol, 16(1), 27-33. doi: 10.1007/s40257-014-0107-3.

DSM Nutritional Products. (2020). Vitamins Basics. Retrieved from https://www.dsm.com/content/dam/dsm/human-nutrition/pdfs/vitamin-basics.pdf

Ducker, G. S., & Rabinowitz, J. D. (2017). One-Carbon Metabolism in Health and Disease. Cell Metab, 25(1), 27-42. doi:10.1016/j.cmet.2016.08.009

Lyon, P., Strippoli, V., Fang, B., & Cimmino, L. (2020). B Vitamins and One-Carbon Metabolism: Implications in Human Health and Disease. Nutrients, 12(2867). doi:10.3390/nu12092867.

Roth, W., & Mohamadzadeh, M. (2021). Vitamin B12 and gut-brain homeostasis in the pathphysiology of ischemic stroke. eBioMedicine, The Lancet, 73(103676). doi:https://doi.org/10.1016/j.ebiom.2021.103676

U.S. Department of Health and Human Services, National Institutes of Health, Office of Dietary Supplements. (2021). Vitamin B12: Fact Sheet for Health Professionals. Retrieved from https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/