Vitamin B12 is essential for red blood cell formation, DNA synthesis, and nervous system function. Found predominantly in animal products, this vital nutrient supports energy metabolism and neurological health. Whilst meat, fish, dairy, and eggs provide rich natural sources, fortified foods offer alternatives for those following plant-based diets. Understanding which foods contain B12 and how much you need daily is crucial for preventing deficiency, particularly for older adults, vegans, and individuals with absorption difficulties. This article explores the best dietary sources of B12 and guidance on meeting your requirements.

What Is Vitamin B12 and Why Do You Need It?

Vitamin B12, also known as cobalamin, is a water-soluble vitamin that plays essential roles in numerous physiological processes throughout the body. This vital nutrient is required for the formation of red blood cells, DNA synthesis, and the proper functioning of the nervous system. Unlike many other vitamins, B12 contains a trace element—cobalt—which gives it its alternative name.

The body relies on vitamin B12 to maintain the myelin sheath, a protective coating around nerve fibres that ensures efficient transmission of nerve signals. Without adequate B12, this protective layer can deteriorate, potentially leading to neurological symptoms such as numbness, tingling, and cognitive difficulties. Additionally, B12 works closely with folate (vitamin B9) in the production of red blood cells; deficiency can result in megaloblastic anaemia, characterised by abnormally large and immature red blood cells that cannot function properly.

Vitamin B12 is unique among vitamins because it is not produced by plants or animals but by certain bacteria and archaea. Humans must obtain it through dietary sources, primarily animal products, or fortified foods. The vitamin requires a complex absorption process involving intrinsic factor, a protein produced in the stomach, which binds to B12 and facilitates its uptake in the small intestine.

Maintaining adequate B12 levels is crucial for energy metabolism, as the vitamin participates in converting food into usable energy. It also helps regulate homocysteine levels in the blood. While elevated homocysteine is associated with increased cardiovascular risk, it's important to note that clinical trials have not consistently shown that lowering homocysteine with B vitamins reduces cardiovascular events.

Foods Naturally High in Vitamin B12

Animal products are the richest natural sources of vitamin B12, as the vitamin accumulates in animal tissues through their consumption of B12-producing bacteria or fortified feed. Understanding which foods contain the highest concentrations can help individuals meet their daily requirements through diet alone.

Meat and poultry are excellent sources of B12. Beef liver stands out as one of the most concentrated sources, with a single 100g serving providing approximately 40μg—well over the UK Reference Nutrient Intake (RNI) of 1.5μg per day. Other organ meats, such as kidney, also contain substantial amounts. Red meat, including beef and lamb, provides good levels of B12, whilst chicken and turkey offer moderate amounts. The vitamin is present throughout the muscle tissue, making these foods reliable dietary sources.

Fish and seafood are particularly rich in vitamin B12. Oily fish such as salmon, trout, and mackerel contain high levels, with a 100g portion of salmon providing approximately 3μg. Shellfish are exceptionally rich sources; clams can provide up to 80μg per 100g. Sardines, tuna, and cod also contribute significant amounts. These marine sources offer the additional benefit of providing omega-3 fatty acids and other essential nutrients.

Dairy products and eggs provide more moderate but still valuable amounts of B12. Milk contains approximately 0.4μg per 100ml, while cheese content varies by type and maturation process. Eggs contain B12 primarily in the yolk, with one large egg providing approximately 0.5-0.6μg, or around one-third of the UK daily RNI. For individuals who consume dairy and eggs but not meat (lacto-ovo vegetarians), these foods become especially important for maintaining adequate B12 status.

The bioavailability of B12 from these natural sources is generally high, though it can vary depending on individual digestive health and the presence of intrinsic factor.

Fortified Foods and Plant-Based B12 Sources

For individuals following plant-based diets or those unable to consume sufficient animal products, fortified foods provide an essential alternative source of vitamin B12. Food fortification involves adding synthetic B12 (typically cyanocobalamin) to products during manufacturing, making the vitamin accessible to those who might otherwise struggle to meet their requirements.

Breakfast cereals are among the most commonly fortified foods in the UK. Many commercial cereals contain added B12, with some providing 25–100% of the UK Reference Nutrient Intake (RNI) of 1.5μg per serving. When selecting cereals, it is important to check the nutrition label, as fortification levels vary considerably between brands and products. Wholegrain varieties often provide additional nutritional benefits alongside the added B12.

Plant-based milk alternatives such as soya milk, almond milk, oat milk, and coconut milk are frequently fortified with B12, along with calcium and vitamin D. A 200ml glass of fortified plant milk typically provides around 25–50% of the daily B12 RNI. However, fortification is not universal, so checking product labels is essential. These alternatives have become increasingly popular and widely available in UK supermarkets.

Nutritional yeast is a deactivated yeast product popular among vegans and vegetarians for its savoury, cheese-like flavour. Many brands are fortified with B12, though unfortified versions contain negligible amounts. Fortified nutritional yeast can provide substantial B12 when used as a seasoning or ingredient. Similarly, some meat alternatives, including certain brands of veggie burgers, sausages, and plant-based mince, are fortified with B12 and other nutrients.

It is important to note that plant foods such as spirulina and most seaweeds contain B12 analogues—compounds that resemble B12 but are not reliably biologically active in humans. While some seaweeds (such as nori) may contain variable amounts of active B12, they should not be relied upon as primary sources. The British Dietetic Association and NHS advise that individuals following strict plant-based diets should prioritise fortified foods or consider B12 supplements to ensure adequate intake.

Who Is at Risk of Vitamin B12 Deficiency?

Vitamin B12 deficiency can develop in various population groups due to inadequate dietary intake, impaired absorption, or increased physiological demands. Recognising those at higher risk enables early intervention and prevention of potentially serious complications.

Older adults face increased risk of B12 deficiency, with prevalence increasing with age. Age-related changes in the digestive system, particularly reduced stomach acid production (atrophic gastritis), can impair the release of B12 from food proteins. Additionally, the prevalence of pernicious anaemia—an autoimmune condition affecting intrinsic factor production—increases with age. Those with symptoms or risk factors should discuss testing with their GP.

Individuals following plant-based diets, including vegans and some vegetarians, are at substantial risk due to the absence of natural B12 sources in plant foods. Without careful planning through fortified foods or supplementation, deficiency is almost inevitable. The Vegan Society and NHS recommend that all vegans take a regular B12 supplement or consume fortified foods daily.

People with gastrointestinal conditions affecting B12 absorption face elevated risk. These include Crohn's disease, coeliac disease, and those who have undergone gastric surgery (including bariatric procedures or gastrectomy). Conditions affecting the terminal ileum, where B12 is absorbed, are particularly problematic. Individuals taking certain medications long-term may also experience reduced B12 absorption, including metformin (for diabetes), proton pump inhibitors and H2-receptor antagonists (for acid reflux), and those with repeated exposure to nitrous oxide (which inactivates B12).

Pregnant and breastfeeding women have increased B12 requirements to support foetal development and infant nutrition. Deficiency during pregnancy can affect foetal neurological development, whilst breastfed infants of B12-deficient mothers are at risk of developmental delays. Women planning pregnancy or who are pregnant should ensure adequate B12 intake, particularly if following plant-based diets.

Symptoms of B12 deficiency develop gradually and may include fatigue, weakness, constipation, loss of appetite, and weight loss. Neurological symptoms such as numbness and tingling in the hands and feet, difficulty walking, memory problems, and mood changes can occur. Seek urgent medical attention for neurological symptoms, visual changes, confusion, or if symptoms occur during pregnancy or in infants. Contact your GP promptly for other symptoms, who can arrange a blood test to assess B12 levels and determine appropriate treatment.

How Much B12 Do You Need Daily?

The recommended daily intake of vitamin B12 varies according to age, physiological status, and individual circumstances. In the UK, dietary reference values are established by the Department of Health and Social Care, with guidance from the Scientific Advisory Committee on Nutrition.

For adults, the Reference Nutrient Intake (RNI) is 1.5 micrograms (µg) per day. This represents the amount sufficient to meet the needs of 97.5% of the population. Most adults consuming a varied diet including animal products can easily meet this requirement through food alone. For context, a 100g serving of salmon provides approximately 3µg, whilst a glass of milk contains around 0.4µg, and one egg provides roughly 0.5-0.6µg (about one-third of the daily RNI).

Children's requirements increase with age. Infants aged 7–12 months require 0.4µg daily, children aged 1–3 years need 0.5µg, those aged 4–6 years require 0.8µg, and children aged 7–10 years need 1.0µg. Adolescents aged 11–14 years require 1.2µg, increasing to the adult level of 1.5µg from age 15 onwards. Breastfed infants rely entirely on maternal B12 status, making adequate maternal intake crucial.

Pregnant women should aim for 1.5µg daily, the same as non-pregnant adults, though some sources suggest slightly higher intakes may be beneficial. Breastfeeding women have increased requirements of 2.0µg daily to ensure adequate B12 in breast milk for infant development.

For individuals with diagnosed deficiency, treatment depends on the cause. For dietary deficiency, oral cyanocobalamin supplements of 50-150µg daily are typically recommended. For those with malabsorption or pernicious anaemia, hydroxocobalamin injections are usually prescribed—1mg intramuscularly on alternate days for 2 weeks (or until no further improvement if neurological signs are present), followed by maintenance injections every 2-3 months (every 2 months if neurological involvement). Very high-dose oral therapy (1000-2000µg) may be considered only when injections are unsuitable and with clinical oversight.

Importantly, if both folate and B12 deficiencies are suspected, B12 should be replaced first to prevent potential neurological harm from treating folate deficiency alone.

Vitamin B12 has a very low toxicity profile, and there is no established upper safe limit in the UK, as excess B12 is readily excreted in urine. However, supplementation should be undertaken with professional guidance, particularly at high doses. If you are concerned about your B12 status or are considering supplementation, consult your GP or a registered dietitian who can assess your individual needs.

Frequently Asked Questions