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What Is Vitamin B12 and What Does It Do?

Vitamin B12, also called cobalamin, is one of the crucial nutrients for DNA synthesis and red blood cell formation. It is a water-soluble vitamin and is easily absorbed into and metabolized by the body. Vitamin B12 is crucial for preventing megaloblastic anemia, a blood condition that makes people tired and weak.

Vitamin B12 Requirements

The vitamin B12 requirements vary according to age and health conditions. An average healthy adult's Recommended Dietary Allowances or RDA of vitamin B12 is 2.4 micrograms. This requirement increases to 2.4 and 2.8 micrograms for pregnant and lactating women, respectively. 

As you age, the absorption of several nutrients, including vitamin B12, is reduced. The RDA for elderly individuals varies from 25 to 100 micrograms.

Food Sources of Vitamin B12

It is quite easy to obtain this vitamin from dietary sources like fish, meat, egg, and dairy products. If you do not consume meat or dairy, you can still get your vitamin B12 from fortified food sources, like plant-based milk, cereals, and grains. 

But natural food sources provide more vitamin B12 than fortified ones. People on vegetarian and vegan diets are at an increased risk for vitamin B12 deficiency.

Vitamin B12 Deficiency Symptoms

Some notable symptoms of vitamin B12 deficiency include pale skin, fatigue, mouth ulcers, mood changes, and confusion. It can also lead to megaloblastic anemia, characterized by the circulation of abnormally large red blood cells. 

Vitamin B12 Deficiency Causes

A common cause of vitamin B12 deficiency is pernicious anemia, in which your immune system mistakenly attacks cells that are required to absorb vitamin B12. 

Other causes of vitamin B12 deficiency may include certain medications like proton pump inhibitors and gastrointestinal disorders like Crohn's disease.

Genetics of Vitamin B12 Deficiency

Genetics is another factor that can influence vitamin B12 levels. Based on your genes, you may be inclined to either have increased or decreased levels of vitamin B12.

The TCN2 gene contains information to produce the transcobalamin 2 protein, which is involved in the transportation of vitamin B12 from blood to the cells in the body. Certain changes in this gene can affect your vitamin B12 levels in the body.

vitamin b12

FUT2 is yet another important gene that influences the absorption of vitamin B12 in the body. FUT2 contains information to produce an enzyme that is necessary for the attachment of a harmful bacteria called Helicobacter pylori to the digestive tract. This bacteria impairs the absorption of vitamin B12 from food.

vitamin b12

Vitamin B12 Genetic Test

You can find out if you have any genetic variations that affect your vitamin B12 levels. This can be done through a genetic test. 

Most genetic tests provide your DNA information in the form of a text file called the raw DNA data. This data may seem like Greek and Latin to you.

We, at Xcode Life, can help you interpret this data. All you have to do is upload your raw data and order a nutrition report. Xcode Life then analyzes your raw data in detail to provide you with comprehensive nutrition analysis, including information on your vitamin B12 levels.



Vitamin B12 is one among the B vitamins and is also known as Cobalamin, since it contains the mineral called cobalt. This water-soluble vitamin cannot be made in the body and needs to be obtained from the food we eat. 

Vitamin B12 helps with the below functions in the body:

Vitamin B12 deficiency can cause irreversible damage to the body and is, unfortunately, an increasing problem in the countries around the world. There are several reasons why your body might be receiving less vitamin B12 than the recommended daily intake. We will talk about that in the coming sections.

The Story Behind Vitamin B12

The story behind vitamin B12 goes as far back as the 1850s and includes the efforts of many renowned pathologists, physicists, and scientists.

Thomas Addison was an English physicist working in the famous Guy’s Hospital in London. Addison was working on the different causes and effects of diseases and identified a condition called Pernicious anemia.

Pernicious anemia is characterized by abnormal and insufficient Red Blood Cells. This disease was considered fatal between the 1800s and early 1900s. 

It took almost 40 years to find a cure for pernicious anemia. George Hoyt Whipple, an American pathologist, had intensely analyzed the effects of food on the disease and concluded that a liver-based diet in dogs helped increase RBC count in the blood. This led to the identification of liver as a food-based treatment option for treating Pernicious anemia. 

While doctors knew this diet helped reverse the condition, they didn’t fully understand why.

It took another 30 years for scientists to successfully identify and remove a water-soluble compound from liver samples and confirm that this was what actually treated the anemia. This compound’s structure was defined in 1956 and was named ‘vitamin B12’. 

There were a total of five Nobel Prizes awarded to scientists around the world for the studies related to vitamin B12. We have these great minds to thank for bringing to the world’s notice one of the most important B vitamins.

Molecular Aspects- Getting Technical

Once you consume foods rich in Vitamin B12, gastric juices in the intestine help release the vitamin from the food. Once the vitamin is free, a particular protein called R-binder attaches itself to B12 and prevents the acids in the stomach from destroying the vitamin B12 molecule. 

Now, the R-binder protein takes B12 to its next destination, the intrinsic factor (IF). This is also a kind of protein produced in the stomach. 

From here, the B12 reaches an important carrier protein called Transcobalamin II. This helps circulate B12 to different parts of the body.

For the proper absorption and circulation of vitamin B12, the gastrointestinal tract and its help are vital. This is why people with gastric issues may have problems absorbing B12. 

Did You Know?

Did you know that your body stores enough quantities of vitamin B12 for future use? If you have been getting enough or more than the daily recommended values of vitamin B12, a certain amount keeps getting stored in the liver. This reserve can last for anywhere between 3 and 5 years! 

The body knows the importance of vitamin B12 and hence keeps a stock of it for your benefit.

If you have been consistently getting lesser vitamin B12 than what’s needed, your excess reserve is continuously used and you start getting signs of vitamin B12 deficiency only after a couple of years.

The rate at which the stored levels are depleted (turnover rate) depends on your body’s ability to get and absorb vitamin B12. Healthy individuals with normal absorption rates may have a lesser turnover rate than those with gastrointestinal issues or pernicious anemia.

Recommended values

The Dietary Reference Intake (DRI) is a reference for assessing the general needs of vitamin B12 levels in children and adults on an everyday basis.

What Does Excess Of Vitamin B12 Lead To?

 Excess of vitamin B12 does not cause toxicity in the body as fat-soluble vitamins do. 

Vitamin B12 that is ingested is used for everyday functioning and a part of it keeps getting stored in the liver as a reserve. The remaining doses are easily excreted out through urine. Hence it is not very easy to get an overdose when it comes to B12.

However, if you are on vitamin B12 shots, supplements, and a diet rich in red meat, poultry, and dairy products simultaneously, excess quantities of the vitamin may cause dizziness, nausea, and headaches in some individuals. 

What Are The Symptoms Of Vitamin B12 Deficiency?

When you are consuming lesser vitamin B12 than the DRI values, you are at risk of developing the below conditions.

Non-genetic Factors Affecting Vitamin B12 Levels

Genetic association

The FUT2 gene encodes a protein that helps a harmful bacteria called Helicobacter pylori attach itself to the digestive tract. This bacteria can inhibit the absorption of vitamin B12 in the body. Here is a list of FUT2 gene variants that can result in increased/ decreased levels of vitamin B12 in the body.

The TCN2 gene encodes a protein that helps in the final transportation of vitamin B12 from the blood to the cells in the body. A certain variant of the TCN2 gene in the Caucasian population is known to cause increased/decreased levels of B12 in the body.

Recommendations for healthy Vitamin B12 levels

Maintaining healthy vitamin B12 levels in the body is beneficial for overall health maintenance. It keeps you energetic, strong, and healthy. Here are expert recommendations on getting your daily dose of vitamin B12 right.


  1. Vitamin B12 is a water-soluble and essential  vitamin that cannot be made in the body. It is available from ingredients you eat, in fortified packaged foods, and in the form of oral supplements and vitamin B12 shots.
  2. Vitamin B12 deficiency can cause a variety of problems including neurological abnormalities, anemia, fatigue and tiredness, and memory issues. It is very difficult to have vitamin B12 overdose. Higher levels are removed from the body through urine.
  3. Non-genetically, factors like age, medications consumed, pregnancy and lactation, and a vegetarian/vegan lifestyle can increase your risk of being vitamin B12 deficient.
  4. Genetically, some people are not able to absorb vitamin B12 from foods and may have lesser levels than what is normal.
  5. A simple blood test will show your vitamin B12 levels. Genetic testing will let you understand if your body is likely to require more vitamin B12 than others. Getting these tests done will help you plan your diet and supplement needs. 


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