Vitamin B12 contains mineral cobalt, which exists in active and inactive forms. Methylcobalamin & 5-deoxy adenosylcobalamin are active, while hydroxocobalamin and cyanocobalamin are inactive and must be converted into active forms to perform certain functions. ⁽¹⁾

Cobalamins are transported by proteins called transcobalamins. 80% of the circulating protein is inactive, while the remaining 20% is active. ⁽²⁾

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Vitamin B12 is mainly animal-based. Sources include ⁽³⁾

• Meat, fish, beef liver, and all dairy products
• Oysters, clams.

Plants do not naturally provide vitamin B12. However, plant-based diets can be fortified with vitamin B12.

Vitamin B12 is essential in keeping neurons and red blood cells healthy. Vit D deficiency may occur due to ^(4,5,6)

1. A diet deficient in Vit B12
2. Intrinsic factor deficiency
3. Gastrectomy(partial or complete)
4. Inflammatory bowel disease
5. Transcobalamins deficiency

The deficiency leads to the following medical conditions, i.e.;

1. Pernicious Anemia⁽⁷⁾
2. Megaloblastic Anemia⁽⁸⁾
3. Neurological disorder(tingling sensations,confusion, depression, and muscle weakness)
4. General physical impairments(feeling nausea, tired, and loss of appetite)
5. Neural tube defects⁽⁹⁾

Supplements come in oral and injectable forms. Oral supplements are advised for individuals having healthy GIT.

Injections are given to patients with pernicious anemia and gastropathy. They are administered intramuscular and subcutaneous. ⁽¹⁰⁾

Intravenous B12 administration is not recommended but can be given through infusion.

No evidence supports the direct role of vitamin B12 injection in weight loss.

However, some human and animal studies suggest the role of Vit B12 in preventing weight gain.

A study on mice reveals the probability of increased adiposity with vitamin B12 deficiency. ⁽¹¹⁾

A study conducted on 3704 patients imparted that B12 deficiency predisposes to increased cholesterol biosynthesis, leading to obesity and cardiac pathologies. ⁽¹²⁾

Low B12 levels are also strongly associated with increased cardiovascular diseases and dyslipidemia. ^(13,14)

Another study found that pregnant women deficient in Vit B12 strongly predispose babies to insulin resistance. ⁽¹⁵⁾

Vitamin B12 prominently helps in cell synthesis and myelination of neurons. In the body, it will boost;⁽¹⁶⁾

• RBC synthesis
• Skin and hair growth
• Cognitive performance
• Cellular metabolism

Indications;

• Pernicious(Addisonian) anemia⁽¹⁷⁾
• Gastropathy or gastric surgery
• Cancer of the bowel or pancreas
• Fish tapeworm manifestation
• Malnutrition/Undernutrition
• Folic acid deficiency

Dosage;

Oral tablets usually contain 500mcg of mecobalamin, but in pernicious anaemia or gastropathy, GIT absorption is minimal, so injectable cyanocobalamin is used.

Most of the pharmaceutical companies manufacture cyanocobalamin in strength of 1000mcg/1mL.

In pernicious anaemia, 100mcg is injected daily for 01 week. If the RBC count improves, the same dose is repeated for the same duration on alternate days, and then 100mcg after every 2-3 days for 2-3 weeks. It is maintained at 100mcg injection every month for whole life. ⁽¹⁸⁾

Some individuals are prone to certain B2 side effects, i.e.⁽¹⁹⁾

• Polycythemia vera
• Anaphylactic shock
• CHF or pulmonary oedema
• Diarrhoea

It would not be a good idea to rely solely on vitamin B12 injections for weight loss. B12 helps maintain optimal cellular and neuronal functions, drives energy by increasing metabolism, and assists in weight loss and toning the body.

1. https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/
2. https://pmc.ncbi.nlm.nih.gov/articles/PMC3257642/
3. https://ods.od.nih.gov/factsheets/VitaminB12-Consumer/
4. https://www.hopkinsmedicine.org/health/conditions-and-diseases/vitamin-b12-deficiency-anemia
5. https://my.clevelandclinic.org/health/diseases/22831-vitamin-b12-deficiency
6. https://www.mayoclinic.org/diseases-conditions/vitamin-deficiency-anemia/symptoms-causes/syc-20355025
7. https://www.cancer.gov/publications/dictionaries/cancer-terms/def/pernicious-anemia
8. https://www.elsevier.es/pt-revista-revista-medica-del-hospital-general-325-articulo-megaloblastic-anaemia-folic-acid-vitamin-S0185106315000426
9. https://academic.oup.com/qjmed/article-abstract/86/11/703/1566278
10. https://www.webmd.com/drugs/2/drug-6550/vitamin-b-12-injection/details
11. https://iubmb.onlinelibrary.wiley.com/doi/10.1002/biof.1350
12. https://link.springer.com/article/10.1186/s13148-015-0046-8#Sec15
13. https://pmc.ncbi.nlm.nih.gov/articles/PMC7400011/#sec8-nutrients-12-01925
14. https://www.sciencedirect.com/science/article/abs/pii/S1043661802000956?via%3Dihub
15. https://www.sciencedirect.com/science/article/pii/S0022316622030863?via%3Dihub
16. https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-b/
17. https://medlineplus.gov/druginfo/meds/a605007.html
18. https://www.drugs.com/vitamin-b12.html
19. https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=953aa8c6-31ce-0c3b-e053-2a95a90ab35f