Vitamin B12: What It Does, Sources, and How to Choose

How it works

Vitamin B12, also known as cobalamin, is a water-soluble vitamin that plays several important roles in the body. It is required for the normal functioning of the nervous system and for normal energy-yielding metabolism, provided the food or supplement is at least a source of vitamin B12. Vitamin B12 is also involved in the formation of red blood cells and DNA synthesis. The body cannot produce vitamin B12 on its own, so it must be obtained from the diet or supplements.

Vitamin B12 is unique among vitamins in that it contains the mineral cobalt at its core, which is why its compounds are called cobalamins. Several forms of cobalamin exist, including methylcobalamin, adenosylcobalamin, cyanocobalamin, and hydroxocobalamin. In the human body, methylcobalamin and adenosylcobalamin are the active forms that participate directly in cellular processes.

One of the most critical functions of vitamin B12 is its role as a cofactor for two enzymes: methionine synthase and methylmalonyl-CoA mutase. Methionine synthase is essential for the synthesis of methionine from homocysteine, a reaction that is crucial for DNA methylation and thus for the regulation of gene expression. Methylmalonyl-CoA mutase is involved in the metabolism of certain fatty acids and amino acids, contributing to energy production.

Vitamin B12 is also necessary for the maintenance of myelin, the protective sheath that surrounds nerves. Myelin is vital for the rapid transmission of nerve impulses. Without sufficient vitamin B12, myelin synthesis is impaired, which can affect the normal functioning of the nervous system.

Vitamin B12 contributes to the reduction of tiredness and fatigue, if the product is at least a source of vitamin B12.

What the research and authorised claims say

According to the European Food Safety Authority (EFSA), vitamin B12 has several authorised health claims, provided the product is at least a source of vitamin B12:

• Vitamin B12 contributes to normal energy-yielding metabolism.
• Vitamin B12 contributes to the reduction of tiredness and fatigue.
• Vitamin B12 contributes to the normal function of the immune system.
• Vitamin B12 contributes to the normal functioning of the nervous system.

These claims are based on a substantial body of research and are only permitted for foods and supplements that meet the minimum threshold to be considered a source of vitamin B12.

Research has also explored the absorption and bioavailability of vitamin B12 from different sources. Naturally occurring vitamin B12 in food is bound to proteins and must be released by stomach acid before it can be absorbed. In contrast, the vitamin B12 found in supplements and fortified foods is typically in a free form, which is more readily absorbed, especially in individuals with reduced stomach acid production.

Studies have shown that vitamin B12 status is influenced by dietary patterns, age, and certain health conditions. For example, older adults may have reduced absorption due to atrophic gastritis, a condition that decreases stomach acid production. People who follow vegan or strict vegetarian diets are at higher risk of low vitamin B12 intake because plant foods do not naturally contain significant amounts of the vitamin.

How much vitamin B12 do people need?

Recommended daily intakes vary by country, but for adults, the typical recommendation is around 2. 4 µg per day. Some groups, such as pregnant or breastfeeding individuals, may have higher needs. For example, pregnant people are often advised to consume 2. 6 µg per day, while those who are breastfeeding may need 2. 8 µg per day.

Children and adolescents have lower requirements, which increase with age. For instance, infants up to 6 months may need about 0. 4 µg per day, while children aged 9–13 years require about 1. 8 µg per day. Meeting these needs is important for growth, development, and the maintenance of normal physiological functions.

Food sources of vitamin B12

Vitamin B12 is naturally found in animal-derived foods. Plant-based foods do not naturally contain vitamin B12, unless they are fortified. Common dietary sources include:

• Meat (beef, pork, lamb)
• Fish and shellfish
• Poultry
• Eggs
• Dairy products (milk, cheese, yogurt)
• Fortified foods (some plant milks, breakfast cereals)

Vitamin B12 content in selected foods

Food	Portion	Vitamin B12 (µg)
Beef liver	100 g	~70
Salmon	100 g	~5
Egg (whole)	1 large	~1. 1
Milk	200 ml	~1
Fortified soy drink	200 ml	~0. 8–1. 2

The vitamin B12 content of foods can be affected by factors such as animal diet, food processing, and cooking methods. For example, boiling milk may slightly reduce its vitamin B12 content, while the vitamin in meat and fish is relatively stable during cooking.

Fortified foods are an important source of vitamin B12 for people who avoid animal products. The amount of vitamin B12 added to fortified foods can vary, so it is important to check the product label to ensure adequate intake.

Vitamin B12 is found almost exclusively in animal-derived foods, unless a product is fortified.

Absorption and metabolism

Vitamin B12 absorption is a complex, multi-step process. In food, vitamin B12 is bound to proteins and must be released by gastric acid and the enzyme pepsin in the stomach. Once freed, it binds to a protein called haptocorrin. In the small intestine, pancreatic enzymes release vitamin B12 from haptocorrin, allowing it to bind to intrinsic factor, a protein produced by the stomach lining. The vitamin B12–intrinsic factor complex is then absorbed in the last part of the small intestine (ileum).

Several factors can impair this process, including low stomach acid (common in older adults), lack of intrinsic factor (as in pernicious anemia), or gastrointestinal surgery that removes or bypasses parts of the stomach or small intestine. In these cases, even a diet rich in vitamin B12 may not be sufficient, and alternative supplementation strategies may be required.

After absorption, vitamin B12 is transported in the blood bound to transcobalamin II, which delivers it to cells throughout the body. The liver stores several years' worth of vitamin B12, which is why deficiency symptoms can take a long time to develop after intake drops.

Key limitations

While vitamin B12 is essential, there are some important limitations and considerations:

• Absorption of vitamin B12 from food can decrease with age or certain medical conditions.
• Strict vegans and some vegetarians may not get enough vitamin B12 from diet alone and may need to consider fortified foods or supplements.

People with gastrointestinal disorders such as Crohn's disease, celiac disease, or those who have had gastrointestinal surgery may also have impaired absorption of vitamin B12, even if their dietary intake is adequate. In these cases, monitoring vitamin B12 status and considering supplementation under medical supervision is recommended.

Some medications can interfere with vitamin B12 absorption. For example, long-term use of proton pump inhibitors (used to reduce stomach acid) or metformin (used for type 2 diabetes) has been associated with lower vitamin B12 levels. Individuals on these medications should discuss their vitamin B12 status with a healthcare professional.

How to choose

With over 700 vitamin B12 products in Tigoo's range, there are several forms and doses available. The most common forms include:

• Cyanocobalamin: A stable, synthetic form commonly used in supplements (113 products in Tigoo's range).
• Methylcobalamin: A naturally occurring, bioactive form (80 products in Tigoo's range).
• Hydroxocobalamin: Another natural form, sometimes used in injections (data not specified in Tigoo's catalog).
• Kobalamin: General term for vitamin B12, used in 104 products in Tigoo's range.
• Vitamin B12 (unspecified form): 31 products in Tigoo's range.

Comparison of vitamin B12 supplement forms in Tigoo's range

Form	Number of products	Typical dose (µg)
Cyanocobalamin	113	6 (median)
Methylcobalamin	80	6 (median)
Kobalamin	104	6 (median)
Vitamin B12 (unspecified)	31	6 (median)

When choosing a vitamin B12 supplement, consider:

• Form: All common forms are effective for increasing vitamin B12 intake. Cyanocobalamin is the most widely used and is stable in supplements. Methylcobalamin is the active form found in the body and is sometimes preferred by those seeking a "natural" option. Hydroxocobalamin is mainly used in clinical settings, such as injections, but is also available in some oral supplements.
• Dosage: The median dose in Tigoo's range is 6 µg per serving, which covers the typical daily recommendation for adults. Some products provide much higher doses (hundreds or even thousands of micrograms), but such high amounts are generally not necessary for most people. The body absorbs only a small fraction of large doses, and excess is excreted.
• Dietary needs: Vegans, vegetarians, older adults, and people with certain medical conditions may have increased needs. For these groups, regular intake of fortified foods or supplements is recommended to maintain adequate vitamin B12 status.
• Product quality: Look for products that clearly state the form and amount of vitamin B12 per serving. Choose reputable brands that follow good manufacturing practices.
• Supplement format: Vitamin B12 supplements are available as tablets, capsules, sublingual (under-the-tongue) tablets, sprays, and liquids. Sublingual forms are marketed for potentially better absorption, but research indicates that oral supplements are effective for most people.

For individuals with absorption difficulties, such as those with pernicious anemia or after certain surgeries, high-dose oral supplements or injections may be recommended by a healthcare professional.

Safety, interactions and risk groups

Vitamin B12 is generally considered safe at recommended doses, as excess amounts are usually excreted in urine. There is no established upper intake level for vitamin B12 because toxicity is rare. However, individuals taking medication, pregnant or breastfeeding people, children, and those with medical conditions should consult a healthcare professional before starting any supplement. High doses are not recommended unless prescribed. Always follow the product's instructions and do not exceed the recommended daily intake. Supplements are not a substitute for a varied and balanced diet.

Vitamin B12 has a very low potential for adverse effects, but rare allergic reactions to supplement ingredients or injection components can occur. People with Leber's disease (a rare genetic eye disorder) should not take vitamin B12 supplements without medical supervision, as high doses may worsen the condition.

Interactions with medications are possible. For example, long-term use of certain antacids, proton pump inhibitors, or metformin may reduce vitamin B12 absorption. People taking these medications should monitor their vitamin B12 status in consultation with a healthcare professional.

Vitamin B12 and special populations

Older adults: As people age, the ability to absorb vitamin B12 from food decreases due to reduced stomach acid production. This makes older adults more vulnerable to low vitamin B12 status, even if their diet appears adequate. Fortified foods or supplements in free (unbound) form are often recommended for this group.

Pregnant and breastfeeding people: Adequate vitamin B12 is important for fetal and infant development, especially for the nervous system. Low maternal vitamin B12 status can affect the developing baby. Supplementation may be necessary for those who do not consume enough animal-derived foods.

Vegans and vegetarians: Because plant foods do not naturally contain vitamin B12, people following vegan or strict vegetarian diets should regularly consume fortified foods or take a vitamin B12 supplement.

People with gastrointestinal disorders: Conditions such as celiac disease, Crohn's disease, or those who have undergone gastrointestinal surgery may have impaired vitamin B12 absorption and may require monitoring and supplementation.