Vitamins are a group of essentialmicronutrients that arerequiredfor maintaining normal cell function, growth, reproduction, development and various metabolic functions in our bodies.Although vitamins are needed in very small quantities, our diet must contain them so that the above mentioned critical functions can be seamless.Generally, vitamins are classified as fat-soluble or water-soluble types.The 13 essential vitamins are listed below.
Of these vitamins, eight of them belong to the vitamin B class often referred to as B complex, which includes vitamins B1, B2, B3, B5, B6, B7, B9 and B12. Vitamin B complex together with vitamin C are known as the water-soluble vitamins which are typically peed out when you get an excess of them (so considered less concerning when taking larger doses), while vitamins A, D, E and K are the fat-soluble vitamins which require you to be more careful so as not to get an excess build-up of them in your body.
The food sources of vitamin B12 are fish, meat, eggs, organ meats such as liver and kidney, poultry, shellfish, milk and milk-derived products, as well as fortified foods like breads, cereals and boxed milks (i.e. soymilk). Vegetarian food contains only a very miniscule amount of vitamin B12. Plants do not absorb cobalamins from the soil.
As a result, vegetable sources essentially do not have vitamin B12.However many bacteria and algae do produce cobalamins. Consuming milk, dairy and soy products in large quantities would be mandatory just to attain the daily B12 requirement because the occurrence of vitamin B12 is very low in milk and soy products (so this is not considered the best option for B12 absorption). Besides natural sources, fortified foods can be considered to get a source of vitamin B12 into one’s diet.
Vitamin B12 exists in four different forms such as cyanocobalamin, methylcobalamin, adenosylcobalamin, and hydroxocobalamin (the chemical structures of the different forms of vitamin B12 are displayed in figure 1 below). Of these four forms, all of them except cyanocobalamin, are bioactive, easily absorbed, and able to positively affect health.
Cyanocobalamin, however, isthe opposite and not so easily absorbed. All four of these forms contain cobalt metal atoms and thus collectively are referred to as cobalamins. Cobalamin consists of a heme-like planar corrin ring structure where four pyrrole nitrogens are coordinated to the central cobalt atom.
Methylcobalamin occurs naturally in the body and assists in producing red blood cells, DNA and takes part in other physiologic functions. It is known to actively participate in the methylation cycle in the body, as well as support folate and methionine metabolism.
It can be found in injection form or as an oral dietary supplement (look for a sublingual or chewable source that you can put under your tongue to dissolve for optimal absorption). It’s been determined through recent studies that intra-muscular and oral B12 absorption are both equally effective for the body.
Figure 1. Different forms of Vitamin B12 and their chemical structures
Adenosylcobalamin, an unstable molecule, exists naturally, is required for energy metabolism, and is harder to find in vitamin B12 supplements (it is more rare and expensive). It is often used by athletes in sports recovery.
Another natural form of vitamin B12 is hydroxycobalamin (or hydroxocobalamin), it’s considered the most well-tolerated form of all the active cobalamins. It’s also known for helping pernicious anemia. It is produced by the bacteria present in the digestive tractand is also available in both injectable and oral forms (the easiest way to take it is in a chewable/sublingual tablet – put it under the tongue for maximum absorption).
Hydroxycobalamin not only has its own mechanism of action within the body as a scavenger of nitric oxide, but it is also readily converted into the active forms, adenosylcobalamin and methylcobalamin, inside the body.
Cyanocobalamin is an artificial form of vitamin B12 containing a cyanide molecule that can be converted into the active form, hydroxocobalamin once inside the body, but only by some people. Many have genetic mutations on theMTR (methionine synthase) and MTRR (methionine synthase reductase) SNPs (single nucleotide polymorphisms) who can’t make this conversion very well and it affects the absorption of cobalamin in the body.
|Estimated average requirement (mcg)
|Recommended nutrient intake (mcg)
|>14 years & Adults