Vitamin B12


Vitamin B12 is a crucial, water soluble vitamin that is required for proper red blood cell formation, neurological function as well as DNA synthesis. In simple terms, B12 absorption occurs in two steps -  the first step occurs in the stomach, where hydrochloric acid (HCl) is released and helps in the separation of vitamin B12 from the food source (typically protein). The second step is the binding of the vitamin B12 to a protein made by the stomach referred to as the intrinsic factor and this helps absorption of the vitamin in the large intestine.

Production of the intrinsic factor is really important and conditions that inhibit its production, such as pernicious anemia, lead to individuals facing troubles absorbing vitamin B12 from their foods and supplements. Specifically, in supplement form, cyanocobalamin, which is a synthetic version of vitamin B12, is a form that our body can easily convert to its active forms for usage. In general, it is a way to fulfill B12 requirements, especially for groups that may be prone to deficiencies (Office of Dietary Supplements - Vitamin B12).

Recommended Intakes

The recommended intakes are taken from the DRI or the Dietary Reference Intakes developed by the Food and Nutrition Board (FNB). The RDA or the Recommended Dietary Allowance is the average daily level of intake in order to meet the nutrient requirements for (97%-98%) of healthy individuals (Office of Dietary Supplements - Vitamin B12).

RDA for Vitamin B12, taken from the Institute of Medicine, adapted by the NIH:

Food Sources of Vitamin B12

Vitamin-B12 is found in fish, poultry, meat, eggs, and mild products. In particular, beef liver and clams are the best sources of vitamin B12. Usually, breakfast cereals and other food products that are fortified with vitamin B12 can also be a good source, especially if you are vegan or vegetarian (Office of Dietary Supplements - Vitamin B12). Supplements such as cyanocobalamin contain 25-250 mcg (micrograms) of vitamin per tablet (“What Are the Recommended Dietary Allowances (RDAs) for Vitamin B-12 (Cyanocobalamin)?”).

B12 Supplements

The primary supplement discussed here is cyanocobalamin, which is the isolated active form of the vitamin.

When thinking of consuming oral cyanocobalamin, carefully follow instructions on the prescription label or instruction sheets and know if you can take it with or without food. If you are pregnant, if you follow a vegetarian diet, or if you breast-feed, your dose may need to change accordingly.

For individuals with pernicious anemia, cyanocobalamin will probably be part of your daily routine and that, not using the medication can lead to irreversible nerve damage in the spinal cord.

Some side effects:

  1. Allergic reactions are possible, check with your doctor to make sure.
  2. Common side effects include diarrhea, numbness or tingling, fever, and itching or rash

*again, please check with your doctor to make sure if your dosage is safe for your body* (“Cyanocobalamin Uses, Side Effects & Warnings.”).

B12 Deficiency

Vitamin B12 deficiency is characterized by the failure to release B12 from food or failure from the B12 binding proteins. Which as initially mentioned, is part of the two step process for vitamin B12 absorption. This causes weakness, constipation, loss of appetite, and nerve problems (numbness and tingling) can also occur. Other symptoms include issues with balance, depression, confusion, and memory - so treatment is extremely important (Office of Dietary Supplements - Vitamin B12).

While most individuals are able to get their daily vitamin B12 intake through the foods they consume, certain groups are vulnerable for vitamin B12 deficiency. Some of these groups include patients with unexplained anemia, unexplained neuropsychiatric symptoms, gastrointestinal diseases (ex. Crohn’s disease)  gastrointestinal manifestations (ex. diarrhea, anorexia), elderly individuals, vegetarians, and alcoholics (“Risk Groups for Vitamin B12 Deficiency.”).

Notably, the malabsorption of vitamin B12 in elderly individuals has gained importance in recent years. Usually the issue with the elderly is not so much in the consumption but rather, in the physiological conditions associated with aging that may inhibit absorption of B12. In simple words, gastrointestinal issues lead to malabsorption -  and a Strasbourg study observing elderly people who had vitamin B12 deficiency found that 55% had malabsorption problems, 33% had pernicious anemia, 11% unexplained, and only 2% due to lack of consumption - which should be noted. Certainly, an obvious solution to this would be to increase the RDA for the elderly so that the low levels of absorptions are compensated with high consumption, thereby naturally improving B12 levels for elderly bodies (“Risk Groups for Vitamin B12 Deficiency.”).

A study conducted by Eussen et al., looked into the supplementation of cyanocobalamin in the elderly with mild B12 deficiency. They found that daily doses of 2.5 to 250 μg

of the supplement produced statistically significant reductions in the level of B12 deficiency by 16% to 23% within this population. Again they did conduct this study on fairly healthy elderly individuals with mild deficiencies so the the main takeaway from the results, which even the researchers found surprising, was that even the lowest dose of oral cyanocobalamin required to reduce deficiency is more than 200 times greater than the recommended dietary allowance of vitamin B12 (Eussen). This gives us insight onto the point made previously on increasing B12 consumption to reduce or help with B12 deficiencies.

Vitamin B12 deficiency is serious and although the other groups haven’t been discussed in detail, in general, either when B12 acceptors are impacted - such as blood (anemia) or  neurological issues - or when the gastrointestinal tract is impacted, vitamin B12 absorption is impacted (“Risk Groups for Vitamin B12 Deficiency.”). As always, maintaining a balanced diet and maintaining one’s health is important and will help you from developing illnesses.


Vitamin B12 consumption is crucial for the building blocks of life, and with numerous groups facing deficiencies due to metabolic abnormalities, supplements such as cyanocobalamin and  synthetic preparations of B12, can be helpful in restoring healthy levels of B12 in the body.