What is Vitamin B12?

Vitamin B12, also known as cobalamin, is a water-soluble vitamin that plays a crucial role in the normal functioning of the brain, nervous system, and the formation of red blood cells. It is one of the eight B vitamins and is essential for maintaining the health of your body.

One of the unique features of vitamin B12 is that it is not naturally produced by our bodies. Instead, it is only found in animal products, such as meat, fish, eggs, and dairy products, or in fortified foods and supplements. This means that individuals following strict vegetarian or vegan diets are at a higher risk of developing a vitamin B12 deficiency and may need to consider supplementation.

What are the benefits of Vitamin B12?

While the body only needs a small amount of vitamin B12, its absence or deficiency can lead to significant health complications. Therefore, understanding the benefits and mechanisms of action of vitamin B12 is crucial for maintaining overall health and well-being.

Red Blood Cell Formation: Vitamin B12 is vital for the production of red blood cells in the bone marrow. These red blood cells carry oxygen throughout the body, ensuring proper cellular function and energy production.

Neurological Function: Vitamin B12 plays a crucial role in maintaining healthy nerve cells and supporting neurological function. It is involved in the synthesis of myelin, a fatty substance that coats and protects nerve fibers, facilitating efficient nerve signal transmission.

DNA Synthesis: Vitamin B12 is necessary for the synthesis of DNA, the genetic material present in all cells. It works in conjunction with folate to ensure proper DNA replication and cell division, crucial processes for growth, development, and tissue repair.

Energy Metabolism: Vitamin B12 helps convert carbohydrates into glucose, which is used as fuel by the body to produce energy. It also aids in the metabolism of fats and proteins, contributing to overall metabolic health.

Supports Heart Health: Adequate levels of vitamin B12 are associated with lower levels of homocysteine, an amino acid linked to an increased risk of heart disease. By helping to metabolize homocysteine, vitamin B12 may help reduce the risk of cardiovascular complications.

Maintains Healthy Skin, Hair, and Nails: Vitamin B12 contributes to the health and vitality of the skin, hair, and nails by supporting cell reproduction and renewal processes.

What are the Side-effects of Vitamin B12?

While vitamin B12 is generally safe when consumed within recommended dosage limits, excessive intake can lead to certain side effects. These may include:

Allergic Reactions: Some individuals may experience allergic reactions to vitamin B12 supplements, characterized by symptoms such as itching, swelling, rash, or difficulty breathing. In such cases, immediate medical attention is necessary.

Digestive Issues: High doses of vitamin B12 supplements may cause digestive discomfort, including nausea, vomiting, diarrhea, or abdominal cramps. These symptoms usually resolve once the dosage is reduced or discontinued.

Hypersensitivity Reactions: Rarely, individuals may develop hypersensitivity reactions to vitamin B12 injections, leading to symptoms such as itching, redness, or inflammation at the injection site.

Interactions with Medications: Vitamin B12 supplements may interact with certain medications, including proton pump inhibitors (PPIs), H2 receptor antagonists, and metformin, reducing their absorption or efficacy.

Risk of Hypokalemia: Long-term use of vitamin B12 supplements at high doses may increase the risk of hypokalemia, a condition characterized by low levels of potassium in the blood.

What are the various types of Vitamin B12?

Vitamin B12 exists in several forms, including:

Cyanocobalamin: Cyanocobalamin is the most commonly used and stable form of vitamin B12 found in supplements and fortified foods. It is converted into methylcobalamin and adenosylcobalamin in the body for use in various biochemical reactions.

Methylcobalamin: Methylcobalamin is the active form of vitamin B12 that is readily absorbed and utilized by the body. It plays a crucial role in neurological function and is often used in supplements targeting nerve health and energy metabolism.

Adenosylcobalamin: Adenosylcobalamin is another active form of vitamin B12 involved in energy metabolism and the synthesis of myelin. It works synergistically with methylcobalamin to support overall health and well-being.

Hydroxocobalamin: Hydroxocobalamin is a natural form of vitamin B12 found in foods and used in injectable vitamin B12 formulations. It has a longer half-life in the body compared to cyanocobalamin and is often preferred for treating vitamin B12 deficiency.

How does Vitamin B12 work?

Vitamin B12 functions as a cofactor for two essential enzymes: methionine synthase and methylmalonyl-CoA mutase.

Methionine Synthase: Methionine synthase converts homocysteine to methionine, an amino acid required for protein synthesis and DNA methylation. This reaction also generates tetrahydrofolate (THF), a form of folate necessary for DNA synthesis and cellular division.

Methylmalonyl-CoA Mutase: Methylmalonyl-CoA mutase converts methylmalonyl-CoA to succinyl-CoA, a critical step in the metabolism of fatty acids and certain amino acids. This process helps maintain optimal energy production and cellular function.

Deficiency of vitamin B12 can impair the activity of these enzymes, leading to the accumulation of homocysteine and methylmalonic acid in the blood, which are associated with various health complications, including neurological disorders, megaloblastic anemia, and cardiovascular disease.

Recommended dosage of Vitamin B12

The recommended daily intake of vitamin B12 varies depending on age, sex, and individual health needs. In general, the Dietary Guidelines recommend the following daily allowances:

Infants (0-6 months): 0.4 micrograms (mcg)

Infants (7-12 months): 0.5 mcg

Children (1-3 years): 0.9 mcg

Children (4-8 years): 1.2 mcg

Children (9-13 years): 1.8 mcg

Adolescents (14-18 years): 2.4 mcg

Adults: 2.4 mcg

Pregnant and lactating women: 2.6-2.8 mcg

Natural and Food Sources of Vitamin B12

Natural and food sources of vitamin B12 are crucial for maintaining optimal health and wellbeing. As a registered dietitian, I am here to provide you with the necessary information on this essential nutrient. Vitamin B12 is primarily found in animal products, making it challenging for individuals who follow a plant-based or vegetarian diet to meet their requirements. Some of the best sources include lean meats, poultry, fish, eggs, and dairy products. For the vegetarian population, fortified foods such as plant-based milk, breakfast cereals, and nutritional yeast are excellent alternatives.

Frequently Asked Question on Vitamin B12

1. What is Vitamin B12, and why is it important?

Vitamin B12, also known as cobalamin, is a water-soluble vitamin that plays a crucial role in several bodily functions. It is essential for the formation of red blood cells, DNA synthesis, nerve function, and the production of brain chemicals. Vitamin B12 is also involved in energy metabolism and helps to convert food into usable energy. Adequate levels of B12 are necessary for maintaining a healthy nervous system, cognitive function, and overall well-being.

2. How can I get Vitamin B12 in my diet?

Vitamin B12 is naturally found in animal-based foods such as meat, poultry, fish, eggs, and dairy products. For individuals following a vegetarian or vegan diet, fortified plant-based foods like breakfast cereals, plant-based milk, and nutritional yeast can be good sources of Vitamin B12.

3. What happens if I don’t get enough Vitamin B12?

If you don’t get enough Vitamin B12, you may develop a deficiency, which can lead to various health issues. Symptoms of B12 deficiency include fatigue, weakness, tingling or numbness in the hands and feet, difficulty in maintaining balance, memory problems, and depression. Prolonged deficiency can result in serious complications, including anemia and irreversible neurological damage.

4. Who is at risk of Vitamin B12 deficiency?

Vitamin B12 deficiency can occur in certain groups of people, including vegetarians and vegans who do not consume fortified foods or take supplements, older adults with impaired absorption, individuals with gastrointestinal disorders like Crohn’s disease or celiac disease, and those who have undergone weight-loss surgeries that affect nutrient absorption. Chronic alcoholics and individuals taking specific medications may also be at an increased risk of B12 deficiency.

5. Can I get enough Vitamin B12 through supplements?

Yes, if you are unable to meet your Vitamin B12 needs through your diet alone, supplements can be an effective way to ensure adequate intake. They are available in various forms like tablets, capsules, and sublingual (under the tongue) sprays. Consult with a healthcare professional or a registered dietitian to determine the right dosage and form of B12 supplementation for you.

6. Can Vitamin B12 help with weight loss?

Vitamin B12 does not directly promote weight loss. However, maintaining adequate levels of B12 is essential for overall health, metabolism, and energy production, which may indirectly support a healthy weight and healthy lifestyle. If you are looking to lose weight, it is important to focus on a balanced diet, portion control, regular physical activity, and seek guidance from a registered dietitian or healthcare professional.

7. Can I overdose on Vitamin B12?

Vitamin B12 is generally considered safe, and an overdose is rare. Since it is a water-soluble vitamin, excess amounts are usually eliminated through urine. However, extremely high doses of B12 supplements may cause some side effects like diarrhea, nausea, or skin rashes. It is always recommended to follow the dosage guidelines and consult with a healthcare professional before starting any supplementation.

8. Can Vegan and Vegetarian diets provide sufficient Vitamin B12?

Vitamin B12 is primarily found in animal-based foods, making it challenging for vegans and vegetarians to obtain sufficient amounts from diet alone. While some plant-based foods are fortified with B12, it is important for individuals following vegan or vegetarian diets to regularly monitor their B12 levels and consider supplementation if necessary. A registered dietitian can help provide guidance on meeting B12 needs through appropriate food choices and supplementation.

9. Can Vitamin B12 improve mood and mental health?

Vitamin B12 plays a role in the production of brain chemicals that regulate mood and cognition. Adequate levels of B12 are essential for maintaining optimal mental health. However, it is important to note that while B12 deficiency can contribute to mood disorders or cognitive decline, simply supplementing with B12 may not be sufficient to treat underlying mental health conditions. It is crucial to seek guidance from mental health professionals if you are experiencing mood-related concerns.

10. Can I get Vitamin B12 from plant-based alternatives like spirulina or seaweed?

Spirulina and seaweed are often promoted as sources of Vitamin B12; however, they contain forms of B12 that are not easily absorbed by the human body. These plant-based alternatives may not provide a reliable source of Vitamin B12, particularly for individuals following vegan or vegetarian diets. It is recommended to focus on fortified foods and supplementation for adequate B12 intake.

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Faye James

Clinical Nutritionist

Nutritionist verified

Experienced Senior Content Designer with an impressive portfolio of collaborations with renowned brands such as Woolworths, Weight Watchers, Fitness First, Barry's, Goodlife and Table of Plenty. Accredited Nutritionist and Cook Book Author, with extensive media coverage in ELLE, Glamour, Harpers Bazaar, Daily Express, Telegraph UK, MailOnline, WHIMN, WHO, New Idea, Girlfriend, Practical Parenting, Kidspot, Good Food, Body and Soul, Prevention, Good Health, Healthy Food Guide, Woman's Weekly, Women's Day, NW, Take 5, TV Week, HELLO! and OK! Author of The Menopause Diet (2023), The Long Life Plan (2018) and creator of The 10:10 Diet (2019). Frequently featured as an expert in Body & Soul, and proud member of Nutrition Council Australia and Associate Member of The Australian Menopause Society.