Main Difference – Vitamin B vs B12
There seems to be a lot of confusion over the difference between vitamin B and vitamin B12. Vitamin B is a water soluble vitamin complex and represents a group of nutritional organic compounds that comprises of Vitamin B1, B2, B3, B5, B6, B7, B9, and B12. Vitamin B complex is particularly significant for the cell metabolism in human body. In contrast, vitamin B12 is a one of the eight B vitamin complexes, and it is also known as cobalamin. It is mainly vital for the red blood cells formation and the function of the brain and nervous system. This is the main difference between vitamin B and vitamin B12. In this article, let’s elaborate the difference between vitamin B and vitamin B12 in terms of their intended uses and other chemical characteristics.
What is Vitamin B
B vitamins are a group of water-soluble essential organic compounds that play a significant role in cellular metabolism. Although these vitamins have more or less similar names, research studies identify that they are chemically different vitamins that frequently co-occur in the similar foods. All B vitamins and their alternative names are listed below;
Vitamin B1 or thiamin
Vitamin B2 or riboflavin
Vitamin B3, niacin or nicotinic acid
Vitamin B5 or pantothenic acid
Vitamin B6, pyridoxine, pyridoxal or pyridoxamine
Vitamin B7 or biotin
Vitamin B9 or folic acid
Vitamin B12 or various cobalamins such as cyanocobalamin or methylcobalamin
What is Vitamin B12
Vitamin B12 is also known as cobalamins, and it is also a water-soluble vitamin. It belongs to the B vitamin complexes, and its major role is to contribute to the regular functioning of nervous and brain system as well as to synthesize red blood cells. In addition, vitamin B12 also contributes to each and every cellular metabolism pathways in the human body because it is essential for synthesis and regulation of DNA, metabolism of amino acids and fatty acids. Humans, other animals or plants cannot produce vitamin B12. Only bacteria and archaea can synthesize vitamin B12. It is the largest and most structurally complex vitamin among all vitamins. It comprises the biochemically very rare constituent cobalt, existing in the center of tetra-pyrrole ring of vitamin B12 structure also known as a corrin ring.
Difference Between Vitamin B and Vitamin B12
The difference between vitamin B and vitamin B12 can be divided into following categories. They are;
Vitamin Group
Vitamin B is a water soluble vitamin complex which comprises of eight different vitamins.
Vitamin B12, also known as cobalamin, generally represent one type of vitamin in vitamin B complex.
Chemical Structure
Different vitamins B have different structures. As an example, the structure of vitamin B1 (thiamine) and B2 (Riboflavin) are given below.
Vitamin B12 has a very complex structure and it is based on a corrin ring. The central metal ion of this ring is cobalt. There are six coordination sites (R – in the figure 2) in this ring and the sixth coordination site, is either a cyano group (-CN), a hydroxyl group (-OH), a methyl group (-CH3) or a 5′-deoxyadenosyl group 
Source
Rich sources of B vitamins include legumes, whole grains, potatoes, bananas, chili peppers, tempeh, nutritional yeast, brewer’s yeast, and molasses. In addition to this plant sources, B vitamins are mainly concentrated in meat, for example, turkey, tuna, and liver. B vitamins can be found in whole grain cereals; processed grains tend to have lower B vitamin content than their unprocessed counterparts. As a result, the B vitamins are sometimes fortified with thiamine, riboflavin, niacin, and folic acid after processing, and they are known as enriched flour. Although beers are a natural source of B vitamins, their bioavailability is very low because drinking ethanol inhibits absorption of thiamine, riboflavin, niacin, biotin and folic acid.
Vitamin B12 rich sources are mainly animal derived foods such as fish, shellfish, meat, liver, eggs, milk, and milk products. Sometimes, breakfast cereals, soy products, energy bars, and nutritional yeast are fortified with vitamin B12. Vitamin B12 is not available from plant products.
Supplements
Vitamin B supplements may either contain all eight vitamin B complex including multivitamins or individual B vitamin supplements.
Vitamin B12 is used as a supplement in many processed foods and is also available in vitamin pill form, nasal spray, or injection. Vitamin B12 is also a common component in energy drinks. These supplements are essential for preventing deficiencies, particularly in vegetarians. Industrial B12 is produced through bacterial fermentation of selected microorganisms.
Significance
As a complex, different types of vitamin B play different roles in the human body. Some of their main roles are as follows.
Vitamin B1, B2, B3 and B5: Form co-enzymes and involved in the energy production for the electron transport chain, the citric acid cycle, as well as the oxidation of fatty acids and carbohydrates
Vitamin B6 – cofactor in amino acid metabolism
Biotin – Involved in the metabolism of lipids, proteins, and carbohydrates
Folic acid acts as a co-enzyme and involved in cell division, neural tube development and the production of red blood cells
Vitamin B12 has multiple roles and they are as follows;
Involved in the cellular metabolism of carbohydrates, proteins, and lipids
Production of blood cells in the bone marrow
Act as a co-enzyme in intermediate metabolism for the methionine synthase reaction
Side Effects
Excess intake of vitamin B supplements may cause temporary side-effects such as restlessness, nausea, and insomnia.
High vitamin B12 level in older people may protect against Alzheimer’s disease and impaired cognitive function. However, excess consumption of vitamin B12 supplements can cause skin and spinal lesions or acne-like rash.
Deficiency
Different types of vitamin B deficiency can cause some of the following diseases.
- Thiamine deficiency causes beriberi.
- Riboflavin deficiency causes ari-boflavinosis.
- Niacin deficiency causes pellagra.
Vitamin B12 deficiency causes macrocytic anemia, raised homo-cysteine, peripheral neuropathy, memory loss, and other cognitive impairments.
Recommended Intake
Different Vitamin B types have different recommended intake levels.
The dietary reference of Vitamin B12 intake for an adult ranges from 4 to 7 µg per day. However, vitamin B12 requirement in pregnant women is 2.6 µg per day and in lactation women is 2.8 µg per day.
In conclusion, vitamin B complex is an essential nutrient to the human body. Vitamin B12 is an essential water-soluble vitamin which also belongs to the vitamin B complex. 
References:
5’-deoxyadenosylcobalamin and methylcobalamin as sources for Vitamin B12 added as a nutritional substance in food supplements – Scientific opinion of the Scientific Panel on Food Additives and Nutrient Sources added to food (2008). EFSA Journal 815, 1–21.
Butler, C. C. (2006). Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency: A systematic review of randomized controlled trials. Family Practice 23(3), 279.
National Academy of Sciences. Institute of Medicine. Food and Nutrition Board., ed. (1998). Dietary Reference Intakes for Thiamine, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, D.C., National Academy Press.
Image Courtesy:
“Cobalamin” by Ymwang42 (talk). Original uploader was Ymwang42 at en.wikipedia – Transferred from en.wikipedia(Public Domain) via Commons
“Riboflavin” by Calvero. – Selfmade with ChemDraw. (Public Domain) via Wikimedia Commons
“Thiamin” by NEUROtiker – Own work. (Public Domain) via Commons
