Vitamin B12: Effects & Daily Requirements

Vitamin B12, also known as cobalamin, is a collective term for a group of chemical compounds classified as water-soluble vitamins. Vitamin B12 plays several roles in the body, including its necessity for metabolism, blood formation, and cell division. A deficiency can lead to long-term nerve damage and other serious health problems. To prevent this, an adequate supply through diet is essential. In some cases, supplementation with vitamin B12 might be necessary.

Vitamin B12 overview

• Vitamin B12, also known as cobalamin, is involved in numerous body functions.
• The daily requirement for healthy individuals aged 13 and above is 4 micrograms according to DGE.
• The daily vitamin B12 intake cannot be met with a plant-based diet alone.
• Severe deficiency can lead to long-term health issues like anaemia and neurological damage.

What is vitamin B12?

Vitamin B12 is not a single vitamin, but rather a group of substances with similar effects. These compounds, known as cobalamins, include methylcobalamin, adenosylcobalamin, and cyanocobalamin. While methylcobalamin and adenosylcobalamin are naturally occurring forms, cyanocobalamin is a synthetic variant often used in dietary supplements.

What role does vitamin B12 play in the body?

Vitamin B12 plays a vital role in several processes within the human body. Cobalamins are essential for:

• Proper red blood cell formation
• Normal nerve function
• Cell division
• Normal homocysteine metabolism
• Immune system function
• Energy metabolism
• Mental health

What is the daily requirement of vitamin B12?

The daily vitamin B12 requirement varies depending on age. According to the German Nutrition Society (DGE):

• From 13 years of age and older: 4 micrograms per day
• For younger children, depending on age: 0.5 to 3.5 micrograms
• Pregnant women: 4.5 micrograms per day
• Nursing women: 5.5 micrograms per day

How to meet the daily vitamin B12 requirement?

The human gut contains bacteria that produce vitamin B12. However, the body cannot effectively utilize this supply, so a regular intake through food is necessary. Significant concentrations of vitamin B12 are found almost exclusively in animal products. Most plant-based foods contain very little of it or forms the human body cannot properly use.

Which foods are rich in vitamin B12?

Examples of foods high in vitamin B12 (µg/100 g):

• Beef liver: 65 µg
• Pork liver: 39 µg
• Oysters: 14.6 µg
• Rabbit: 10 µg
• Herring: 9.7 µg
• Mackerel: 9 µg
• Lamb: 2.6 µg
• Beef: 2 µg
• Gouda cheese: 2.2 µg
• Eggs: 1.9 µg

Can algae be a source of vitamin B12?

Although algae are frequently promoted as a potential vitamin B12 source, particularly for those following a vegan diet, relying on them can be problematic. The instability of B12 content in many algae species means that the levels can vary significantly depending on the type of algae, its growth conditions, and processing methods. Moreover, even when B12 is present, the human body often struggles to absorb it effectively from these sources. The presence of vitamin B12 analogues, which resemble real B12 but lack the same biological function, can further complicate things by competing with genuine B12 during absorption, potentially reducing the overall amount available for the body to use. While Chlorella algae stands out as a possible exception, more research is needed to determine its reliability as a consistent B12 source. For most vegans, fortified foods or supplements remain the safest and most effective way to meet their B12 requirements.

What causes vitamin B12 deficiency?

Healthy individuals can generally meet their vitamin B12 needs through regular consumption of animal products. However, various factors like diet, certain diseases, and medications can cause a deficiency.

Vitamin B12 deficiency in a vegan diet

Plant-based foods generally contain very little or no usable vitamin B12. As a result, vegans cannot meet their vitamin B12 needs through diet alone. To avoid deficiency, they should take a properly dosed B12 supplement regularly.

Medical causes of vitamin B12 deficiency

• Chronic gastritis, which affects the production of intrinsic factor, necessary for B12 absorption.
• Chronic diseases like Crohn’s disease or liver and kidney disorders.
• Older adults often produce less stomach acid, leading to deficiency over time.
• Medications like acid blockers or metformin for Type 2 diabetes can contribute to B12 deficiency.

What are the effects of a vitamin B12 deficiency?

Although vitamin B12 is water-soluble, the liver stores about 5 mg of it, so symptoms may take years to appear. Prolonged deficiency can cause anaemia, neurological damage, and may even increase the risk of dementia over time.

Symptoms of vitamin B12 deficiency

Common symptoms of a prolonged deficiency include:

• Pale skin and mucous membranes
• Coordination difficulties
• Tingling and numbness in the hands and feet
• Paralysis
• Fatigue
• Muscle weakness
• Vision problems

Elevated homocysteine levels due to folic acid and vitamin B12 deficiency

Homocysteine is an intermediate product in amino acid metabolism. Elevated levels of homocysteine in the blood may increase the risk of cardiovascular diseases like atherosclerosis. Deficiency in folic acid, as well as vitamins B2, B6, and B12, can cause high homocysteine levels.

Can you overdose on vitamin B12?

When consumed through food, a vitamin B12 overdose is virtually impossible. Overdose risks exist primarily with intravenous administration. Some diseases, like polycythaemia vera or liver metastases, can also cause excess vitamin B12 levels.

How dangerous is a vitamin B12 surplus?

Regular intake of vitamin B12, even in higher doses, is generally considered safe and unlikely to cause side effects. Issues only arise in rare cases, such as when B12 is administered intravenously or applied externally.

• The European Food Safety Authority (EFSA) has not yet set an official maximum daily dosage for vitamin B12.
• The German Federal Institute for Risk Assessment (BfR) considers an additional intake of up to 25 micrograms per day, on top of normal dietary sources, to be safe.

Can vitamin B12 increase lung cancer risk?

Some studies suggest that excessive vitamin B12 intake (over 55 micrograms daily from supplements) may increase the risk of lung cancer, particularly among smokers. However, there is also a slight risk for non-smokers.

Can you take vitamin B12 supplements freely?

As long as you stay within recommended limits, taking a vitamin B12 supplement poses no risks. Vegans, vegetarians, and people with certain medical conditions can benefit from supplementation if necessary.

Regular testing of B12 levels provides clarity

To ensure proper dosage, it’s advisable to regularly monitor vitamin B12 levels in the blood. Repeated testing helps keep track of long-term levels. A useful biomarker for early deficiency is Holo-Transcobalamin (Holo-TC), the active form of the vitamin in the body.

Important to know

If you are not a medical professional and have complaints, specific health conditions, or suspect deficiencies, please make sure to consult a doctor to discuss this.