What happens when your vitamin B12 is low? – Methyl-Life Supplements

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What happens when your vitamin B12 is low?

What happens when your vitamin B12 is low?

Vitamin B12 plays an important role in the cell's metabolism. Our body needs vitamin B12 to maintain the functioning of the nervous system, the health of the red blood cells, and to synthesize nucleic acids (our genetic material).

B12 is also involved in the metabolism of homocysteine, which is associated with cardiovascular diseases when levels are high in our blood. Like most vitamins, B12 can´t be synthesized by our bodies, thus we must get it from food or supplementation.

The problem is some people don´t consume enough B12 to meet their needs. Other´s simply can´t absorb it, no matter how much they intake.

This can be due to pernicious anemia, reduced levels of stomach acidity, intestinal disorders or even genetic variants preventing enzymatic conversion.

For this reason, B12 deficiency is a common health problem, especially among elderly people. B12 deficiency affects between 2.5 and 26 % of the general population, depending on the definition used.

Most of the time, the cause of this deficiency is dietary inadequacy. That's why vegans, vegetarians, and individuals who cannot absorb Vitamin B12 may benefit from its supplementation, and from a diet containing B12-rich food.


What are the sources of B12 vitamin?

Vitamin B12 is naturally found in animal products such as fish, meat, poultry, eggs, and milk. There are also fortified cereals available (however, watch out for the type or form of B12 used, if it’s cyanocobalamin, the likelihood is much lower than the body will be able to use it).  And of course, there are B12 supplements. 


Be Sure to Check Out Our B-12 Collection Below:


Active B12 Complete - 3 Fully-Bioavailable forms of B12 - 3 month supply - Chewables


Vitamin B12 - Hydroxocobalamin - the most well-tolerated bioavailable form - 3 month supply

 B12 Vitamins Supplements

B-Methylated-II - L-Methylfolate 3 mg + Methylcobalamin 3.75 mg - Pregnancy/Cardiovascular/Nerve Health - 3 month supply

 b12 Vitamins SupplementsMethylfolate 7.5+ - Mood Lift - Purest L-Methylfolate + Active B12s - 3 month supply - Chewables


How is dietary vitamin B12 absorbed?

B12 is bound to protein in food and requires release by gastric acid and pepsin in the stomach. Once it's free, it attaches to proteins in the saliva, and are transported to the small intestine where they bind to the intrinsic factor, a protein produced by the gastric cells. In the ileum, it's digested, and released in the bloodstream. 


What are the dietary requirements for vitamin B12?

According to the National Institutes of Health (NIH), the recommended intake of vitamin B12 is 0.4 mcg for children, and 2.4 mcg for adults. Higher amounts may be necessary during pregnancy and lactation.


The risk factors for B12 deficiency

There are several reasons why a person's vitamin B12 may be low. This makes it more difficult to identify people susceptible to supplementation. Usually, this vitamin deficiency is caused by one or more factors. The most common are:

  • Pernicious anemia: it´s when the body cannot absorb vitamin B12 from food because it lacks a specific protein (intrinsic factor) in the stomach. Consequently, it can´t make enough red blood cells. The risk of developing this disease increases with age. 
  • Gastrointestinal surgery: people who have had stomach reduction surgery, for example may have reduced absorption of vitamin B12.
  • Low intake of B12-rich food.
  • Gastrointestinal infections or infestations, such as Helicobacter pylori (bacteria found in the stomach).
  • The use of certain drugs such as heartburn drugs, which reduce acid production in the stomach (acid is needed to absorb vitamin B12).
  • The presence of certain diseases such as HIV, malaria, and tuberculosis.
  • Celiac or Crohn´s disease are conditions that interfere with nutrient absorption.
  • MTR and MTRR are genetic SNPs (single nucleotide polymorphisms) which can play an important part in the enzymatic conversion of B12 within the body, therefore hindering absorption if variants are present.


The groups of risk for vitamin B12 deficiency

  • People 60 years and older.
  • Pregnant women: during pregnancy, several physiological changes occur in the woman's body, which have an impact on vitamin B12 levels. 
  • Children: while growing up, demand for vitamin B12 is high. Low maternal vitamin B12 status, extended breastfeeding, and a low intake of animal food after weaning are major risk factors for B12 deficiency.


What happens to your body when your B12 is low?

Because it is a slow-progressing condition and has varying symptoms, vitamin B12 deficiency is often under-diagnosed. However, symptoms of B12 deficiency may be serious and impact your overall health and quality of life. 


At the cellular and molecular level

When you don't have enough B12 vitamin, this may lead to homocysteine accumulation and reduced synthesis of methionine and SAMe (S-adenosylmethionine). 

Homocysteine is an amino acid present in your blood. Its accumulation can induce cellular stress and apoptosis (cellular death), and it's related to the occurrence of cardiovascular diseases and a weakened immune system. 

Methionine is another amino acid used to build proteins in your body, and S-adenosylmethionine is a methyl donor that is required for the regulation of gene expression. 

B12 deficiency is also linked to a reduction in the expression of a protein called NAD+-dependent protein deacetylase sirtuin 1 (hSIRT1), an increase in acetylation of heat shock factor 1 (HSF1), and the impaired expression of heat shock proteins, involved in oxidative stress.


Neurological problems

B12 deficiency affects the nervous system, resulting in damage to the protective layer of the nerve cells in a process called demyelination. Neurons responsible for sensing vibrations and body position are especially susceptible to this demyelination, but motor neurons (used to contract the muscles) can also be affected. 

In children, signs and symptoms may vary depending on the duration and severity of this deficit. Treatment with B12 is capable of reversing motor impairment, although prolonged deficiency can result in permanent developmental disabilities. Low maternal B12 levels during pregnancy may cause neural tube defects (a narrow channel that forms the brain and spinal cord) in the baby. When this happens, malformations in the spine and brain may occur. 

The increased levels of homocysteine as a consequence of low B12 levels are associated with cognitive impairment, especially in older people.

Other symptoms may be present, such as numbness, tingling of the hands and feet, difficulty walking, memory loss, disorientation, dementia, and mood changes. The progression of these neurological symptoms is gradual. Whatever can be reversed with treatment will depend on the severity and duration of the deficiency. 


Hematological manifestations

When B12 is deficient, there is an impairment in DNA synthesis which affects the division of cells, especially the ones that divide quickly. This leads to an unbalanced growth in dividing bone marrow cells, producing abnormally large cells with immature-looking genetic material. This predominantly affects precursors of the red blood cells, giving rise to megaloblastic anemia.

Other hematopoietic cells can be affected, and a decrease in the number of all blood cells can be observed. 

Red blood cells are the ones that carry oxygen to our organs and systems. Without them, there would not be enough oxygen for them to function properly. 

Symptoms of megaloblastic anemia are:

  • Shortness of breath
  • Muscle weakness
  • Abnormal paleness of skin
  • Swollen tongue
  • Diarrhea
  • Nausea
  • Fast heartbeat
  • Numbness in extremities
  • Fatigue


Gastrointestinal symptoms

Low B12 is associated with inflammation due to the destruction of the lining of the stomach. Other symptoms that can be observed are:

  • Loss of appetite
  • Tongue soreness
  • Constipation

Other health problems associated with low vitamin B12

Cardiovascular diseases

Together with folate and vitamin B6, vitamin B12 is involved in the metabolism of homocysteine. When B12 is low, the levels of homocysteine rise, which is related to an increased risk in the incidence of heart diseases and stroke. 

It’s worth noting that, L-Methylfolate and B12 supplementation is known to decrease homocysteine levels in the blood.



The deficiency of vitamin B12 can cause damage to our genetic material and alter DNA methylation (the addition of methyl groups to a DNA molecule), thus interfering with gene expression regulation mechanisms. 

This damage in the DNA can lead to chromosomal breaks in the white blood cells. And all of these things increase the potential for chances of cancer development.

Moreover, people who suffer from pernicious anemia are at increased risk of developing stomach cancer. 



Vitamin B12 deficiency can sometimes lead to difficulties trying to in conceive, which usually improves after appropriate treatment.  



Research studies have demonstrated that low vitamin B12 levels are linked to higher rates of depression. The reasons for this are not clear yet but may likely involve the shortage of S-adenosylmethionine (SAM), a methyl group donor for numerous methylation reactions in the brain, including those involved in the metabolism of neurotransmitters. Particularly serotonin as its deficiency is related to depression.


Treatment for vitamin B12 deficiency

Vitamin B12 replacement therapy can correct anemia, although neurological symptoms improvement will depend on the amount of damage already done. 

The treatment at a doctor’s office is usually done through intramuscular injections of cyanocobalamin. Cyanocobalamin is the most common form of vitamin B12 used. But be aware that although it is inexpensive, it is also a man-made synthetic, has cyanide in it, and does NOT convert well in the body - especially if you have genetic variants which hinder B12 enzymatic conversion. In oral supplements you will find it most common and the only form used in food fortification, but other forms of B12 can be found.

Methylcobalamin is probably the second most well-known form of B12 and it’s also the most converted and ready for bioavailable absorption by the body. The other two active B12s ready for use by the body directly are more rare and expensive, but well-worth the extra costs.

Hydroxocobalamin and Adenosylcobalamin. Both can be found in health supplements but may be hard to get (Google considers the B12 form hydroxocobalamin as a ‘pharmaceutical’ and does not allow supplement companies to sell it using their platform).

All 3 active forms of the B12 nutrient (hydroxocobalamin, methylcobalamin and adenosylcobalamin) will provide a superior B12 deficiency treatment approach due to the body’s ability to use them immediately. No need for a long and complex conversion process fraught with roadblocks to complicate it.

Over-the-counter preparations containing cyanocobalamin include multivitamins, vitamin B-complex supplements, and single-nutrient, vitamin B12 supplements. But these may not be of much help to you.

So carefully seek out the active versions of B12 and be sure to get a form that is absorbed through the mucosa membrane in the mouth (by holding the nutrient under your tongue and letting it dissolve). This will maximize the effectiveness of your B12 treatment approach.

Of course, some doctors can get the active forms in injection or IV form, however, the costs would be exorbitant, so look for a solid, full-spectrum supplement option and make it easy on yourself. 

Methyl-Life™ makes a great 5000 mcg vegan tablet which contains all 3 active forms of B12 that can be taken sublingually. They also have a hydroxocobalamin form only product which has 2500 mcg of B12 – known to be the most well-tolerated form.

If you happen to know your genetic status for the two SNPs COMT 158 and VDR Taq, you can learn more specifically which active type(s) your body will benefit from most. Check out the details here.

The percentage of vitamin B12 absorption improves with supplementation; therefore, patients 50 years and older, pregnant women, vegans or strict vegetarians, those with malabsorption conditions, as well as people genetically challenged on this biopathway should consume foods fortified with vitamin B12 and/or take vitamin B12 supplements.

Vitamin B12 is essential in numerous physiological processes for our physical and mental health. It is important to pay attention to the consumption of the recommended daily amounts to maintain the functioning of our brain and cellular metabolism. If this is not possible, supplementation is a viable option.

It is also important to be aware of the signs and symptoms of vitamin B12 deficiency, the treatment if done in time is effective. Some people may need special attention, such as pregnant women, the elderly, and people who do not eat animal products.






Green, Ralph, et al. "Vitamin B 12 deficiency." Nature reviews Disease primers 3.1 (2017): 1-20.


Salinas, M., et al. "Vitamin B12 deficiency and clinical laboratory: lessons revisited and clarified in seven questions." International journal of laboratory hematology 40 (2018): 83-88.

    Written By,
    - Jamie Hope



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