Vitamin B12: why do I need it?

The roles of vitamin B12 

The nutritional reference value for the adult population for vitamin B12 is 2.5 mcg/day [1]. 

Vitamin B12 is necessary for development, myelination (an essential process for neuronal function), the functioning of the central nervous system, the formation of healthy red blood cells, and DNA synthesis [2].
 

Vitamin B12 has two active forms with distinct roles [3]. 

What is the link between vitamin B12 and folate?

Certain dietary folates and folic acid are metabolised into 5-methyltetrahydrofolate (5-MTHF, the active form of folate), which donates its methyl group to convert homocysteine into methionine. This reaction depends on an enzyme, methionine synthase (MS), which requires vitamin B12. 

In the event of a vitamin B12 deficiency, 5-methyltetrahydrofolate (5-MTHF) will not be converted into tetrahydrofolate, which will lead to a functional folate deficiency and impaired synthesis of DNA bases[4]. 

Did you know? Folic acid found in food supplements can be metabolised into tetrahydrofolate even in the case of vitamin B12 deficiency. As a result, folic acid can mask the signs of vitamin B12 deficiency, delaying its diagnosis and allowing the neurological complications of vitamin B12 deficiency to progress unchecked [5].

Furthermore, vitamin B12 itself also depends on folate! For the various forms of vitamin B12 to be converted into methylcobalamin, they require 5-methyltetrahydrofolate to donate its methyl group [6]. 

These two vitamins are therefore closely linked, and an adequate intake of folate and vitamin B12 is essential for the body.

Our women's multivitamin Mama essentials is rich in vitamins B12 and B9. 

What are the possible causes of vitamin B12 deficiency?

One cause of vitamin B12 deficiency is difficulty absorbing vitamin B12 from food. Food-cobalamin malabsorption is characterised by the inability to release vitamin B12 from food or intestinal transport proteins. Absorption of free-form vitamin B12 is generally not affected in individuals with food-cobalamin malabsorption [7].

Other causes include the absence of intrinsic factor, which enables vitamin B12 absorption, gastrointestinal surgery, prolonged use of certain medications (for example, metformin, a medication used for diabetes) and dietary deficiency (see below) [8].

Certain congenital conditions, such as hereditary abnormalities of intrinsic factor and congenital vitamin B12 malabsorption (Imerslund-Gräsbeck syndrome), can also lead to severe vitamin B12 deficiency [9].

Who is at risk of a vitamin B12 deficiency?

Several categories of people are at greater risk of developing a vitamin B12 deficiency.

What are the symptoms of vitamin B12 deficiency?

The effects of a vitamin B12 deficiency may include megaloblastic anaemia (characterised by large abnormal red blood cells), as well as low white blood cell, red blood cell and platelet counts, inflammation of the tongue, fatigue, palpitations, pale skin, dementia (loss of cognitive function), weight loss, and infertility. Neurological changes, such as numbness and tingling in the hands and feet, may also occur [14].

Vitamin B12 requirements increase during pregnancy, rising to 4.5 mcg/day [15]. The Elfe study found that intake was insufficient in 25 to 50% of women.

Vitamin B12 concentrations at optimal levels prior to conception are associated with a 60% reduced risk of preterm birth [16]. 

However, it has been observed that deficiency in the mother is associated with an increased risk of early and recurrent miscarriage, preterm birth and low birth weight [17]. 

Serious abnormalities in the development of the central nervous system, such as neural tube defects, are associated with vitamin B12 deficiency in the mother [18]. Indeed, studies highlight an association between high homocysteine levels and neural tube defects; in the absence of vitamin B12, homocysteine is not converted into methionine and its concentration increases in the body [19]. Irish researchers have shown that vitamin B12 deficiency increases the risk of neural tube defects by 2.5 to 3 times [20].

If you are taking any, check that your pregnancy vitamins contain methylcobalamin.

After giving birth, many mothers report experiencing mommy brain, which refers to a cluster of symptoms such as memory difficulties, inability to concentrate, trouble processing information, fatigue and scattered thoughts.

A recent study of 39,000 people found that low vitamin B12 levels were associated with attention and memory difficulties [21].

Another study conducted with 202 people experiencing cognitive difficulties and low or deficient vitamin B12 levels found that B12 supplementation led to an improvement in cognition in 84% of participants and an improvement in memory and attention test scores in 78% of participants [22]. Our post-partum food supplement is rich in vitamin B12. 

Bonus: vitamin B12 may also help with postnatal depression. Depression has been linked to low levels of B vitamins and/or high levels of homocysteine, and vitamin B12 helps precisely to convert homocysteine [23].

To find out more, take a look at our article onpost-partum nutrition.

Vitamin B12 requirements increase during breastfeeding to 5 mcg/day. 
 

The vitamin B12 content of breast milk determines the status of exclusively breastfed infants and is strongly correlated with the mother's blood vitamin B12 levels and maternal intake [24]. As such, a suboptimal vitamin B12 intake will affect the concentration of this vitamin in breast milk. The presence of anaemia in the mother is also associated with significantly lower cobalamin concentrations in breast milk [25].

Infants exclusively breastfed by women with little or no vitamin B12 intake may have very limited reserves of this vitamin and may develop a deficiency sometimes very early in life (from 6 months). Infant deficiency can be serious, especially if the mother's deficiency is severe or caused by pernicious anaemia. Undetected and untreated vitamin B12 deficiency in infants can lead to neurological damage, growth retardation, developmental delays and anaemia [26]. A breastfeeding supplement rich in vitamin B12 may be an option to help ensure your needs are met. 

Sources of vitamin B12 

Vitamin B12 is found in certain foods, predominantly those of animal origin.

The absorption of dietary vitamin B12

Vitamin B12 is bound to food proteins and must be released before it can be absorbed. In the mouth and stomach, vitamin B12 is released and then bound to a binding protein. Once in the duodenum (the initial segment of the small intestine), digestive enzymes release vitamin B12 from its binding protein, after which it combines with intrinsic factor, a transport and delivery binding protein. The resulting complex is absorbed in the terminal part of the small intestine [28]. 

The estimated bioavailability of dietary vitamin B12 varies depending on the dose, as absorption decreases considerably when the intrinsic factor capacity is exceeded. It is generally accepted that 50% of the vitamin B12 ingested through food is actually absorbed by the body [29]. Bioavailability also varies depending on the type of food source. For example, some data suggest that the bioavailability of vitamin B12 may be higher in dairy products than in meat, fish or poultry. 
 

Did you know? Spirulina is not a source of vitamin B12 that can be absorbed by humans. It actually contains a pseudo-cobalamin that our body cannot assimilate [30]. 
 

On the other hand, when vitamin B12 is added to fortified foods and food supplements, it is already in free form and therefore does not require the separation step. The bioavailability of vitamin B12 from food supplements is approximately 50% higher than that from dietary sources, which may be due to the fact that the vitamin is in free form, increasing its absorption [31].

Forms of vitamin B12 in supplements 

Vitamin B12 exists in 4 forms. Studies show that ingesting all four forms of cobalamin can increase vitamin B12 status. 

Cyanocobalamin should be avoided

However, the form cyanocobalamin must be broken down into cobalamin and cyanide to be converted into active forms of vitamin B12 in the human body. This reaction may not be efficient in people with mutations (SNPs) in the B12 metabolic pathways. Ingestion of cyanocobalamin results in lower tissue retention of active vitamin B12 than natural forms of B12 [32]. Moreover, even at low doses, ingestion of cyanocobalamin leads to the release of a cyanide molecule in the body, which is not without consequence.  

Hydroxocobalamin is not a good form

Regarding hydroxocobalamin, its form can increase vitamin B12 status just as effectively as the methyl or adenosyl forms [33]. 

However, hydroxocobalamin may inhibit the enzyme nitric oxide synthase, which can lead to hypertension [34]. In the case of pregnancy, nitric oxide regulates, among other things, embryo development and also controls the vascular tone of the placenta [35]. 

Methylcobalamin is active!

The methylcobalamin is directly active. The fact that cobalamin is directly methylated means it can enter the methylation cycle without first receiving a methyl group, allowing the body to save energy. Always choose a women's food supplement that contains this form.

Adenosylcobalamin is already active!

Adenosylcobalamin is also directly usable, and can even be readily converted into methylcobalamin in the body according to its needs. Furthermore, the methylation required for the conversion from adenosyl to methyl form does not involve the MTHFR gene (the gene involved in folate metabolism). Therefore, a mutation in this gene should not interfere with the conversion of this form. 

Vitamin B12 is essential for the body, particularly for cognitive development and DNA synthesis. Its roles are closely linked to those of folate, so an optimal intake of both vitamins is essential. 
 

The consequences of a deficiency are wide-ranging, including anaemia and neurological problems. During pregnancy, a deficiency can affect the outcome of the pregnancy, and poor intake during breastfeeding can limit the child's development. 
 

It is therefore important to monitor your vitamin B12 intake, particularly for those who do not consume animal products. If you are supplementing with vitamin B12, make sure to check the molecule used, especially if you have an SNP mutation. 

Be careful with self-supplementation! Before deciding to take any supplement, always seek the advice of your doctor or a healthcare professional, particularly to ensure the correct dosage.