Vitamin B12

Vitamin B12, also known as cobalamin, is a water-soluble vitamin essential for nerve function, DNA synthesis, and red blood cell formation. It plays a critical role in energy metabolism by aiding the conversion of food into usable energy. The body stores B12 in the liver, which can sustain needs for several years, but deficiencies may still arise due to absorption issues or dietary restrictions. Research highlights its importance in preventing megaloblastic anaemia and supporting neurological health, with studies emphasising the risks of deficiency in older adults and vegetarians.

Key Facts

• Adults require approximately 1.5 µg of vitamin B12 daily, though needs may increase with age due to reduced absorption.
• Natural B12 sources include meat, fish, eggs, and dairy, while fortified cereals and nutritional yeast cater to plant-based diets.
• Deficiency can cause fatigue, nerve damage, and cognitive issues, often developing insidiously over the years.
• Up to 30% of older adults struggle to absorb B12 from food, making supplements or fortified foods crucial.
• High-dose oral supplements (1,000–2,000 µg) are as effective as injections for correcting deficiencies in most cases.
• Excess B12 is generally non-toxic, though elevated blood levels may signal underlying health conditions like liver or kidney disease.

What does the research say about vitamin B12 and its function in the body?

Vitamin B12 supports nerve myelination, red blood cell production, and DNA synthesis. Research confirms its role in preventing megaloblastic anaemia and mitigating neurological symptoms like tingling or memory loss. Studies also note its limited efficacy in improving cognitive decline unless a deficiency is present.

What are the primary food sources of vitamin B12?

Animal products like beef, salmon, eggs, and dairy are rich natural sources. For those avoiding animal-derived foods, fortified plant milks, breakfast cereals, and nutritional yeast provide alternatives. Absorption from fortified foods varies, so regular intake is advised.

How to supplement vitamin B12?

Supplements come as tablets, sublingual drops, or injections. High-dose oral cyanocobalamin (1,000–2,000 µg daily) is effective for most people, while injections are reserved for severe deficiencies or absorption issues. Sublingual forms bypass stomach absorption barriers.

What are the main symptoms of vitamin B12 deficiency?

Early signs include fatigue, pale skin, and glossitis (a sore tongue). Neurological symptoms like numbness, balance issues, and cognitive fog may follow. Prolonged deficiency risks irreversible nerve damage or megaloblastic anaemia.

Are there any known side effects of supplementing vitamin B12?

B12 supplements are generally safe, with no established upper limit. Rare side effects include mild diarrhoea or itching. Elevated blood levels may indicate underlying conditions like liver disease but aren’t directly harmful.

How long does it take to see the benefits of vitamin B12 supplementation?

Symptom improvement varies: energy levels may rise within days, while neurological recovery can take months. Consistent supplementation typically normalises blood markers like homocysteine within weeks.

What to look for on the supplement label when supplementing vitamin B12?

Opt for methylcobalamin or cyanocobalamin forms, which are well-researched. Check for doses aligning with needs—2.4 µg daily for maintenance or 1,000–2,000 µg for deficiency. Vegan certifications ensure no animal-derived ingredients.

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Can vitamin B12 improve energy levels in non-deficient individuals?

No evidence supports energy-boosting benefits in those with adequate levels. Claims linking B12 to enhanced athletic performance or stamina are unsubstantiated unless a deficiency exists.

Does vitamin B12 interact with medications?

Proton pump inhibitors (e.g., omeprazole) and metformin can reduce absorption. Long-term users of these medications may require higher supplemental doses or regular monitoring.

Is vitamin B12 important during pregnancy?

Adequate B12 is vital for foetal development, particularly for the nervous system. Deficiencies increase risks of neural tube defects, making prenatal supplements with B12 advisable for expectant mothers, especially vegetarians.

Written by Gintare Sukyte