The Label
Vitamin B12 — 6 mcg
Required before any skin cell can copy its own DNA. Here is what it is, what it does, and what our figure means.
What Vitamin B12 Is
Vitamin B12 is the largest and most structurally complex vitamin there is, built around a cobalt atom held in a corrin ring. Nothing in the plant kingdom makes it. It is produced by bacteria, and it reaches us through animal foods where those bacteria have done their work upstream.
Our panel uses methylcobalamin, the form that participates directly in the methylation reaction described below rather than requiring conversion first.
What It Does
Keeping folate working
B12 hands a methyl group to the enzyme that regenerates folate into its usable form. Without functioning B12, folate becomes trapped in a form the cell cannot use — the so-called methyl folate trap. This is why B12 deficiency and folate deficiency produce the same picture in the blood, and why a panel carrying one should carry the other.
In DNA replication
Because folate carries the carbon atoms DNA is built from, and because B12 keeps folate in circulation, a B12 shortfall stops cells dividing properly. The tissues that divide fastest feel it first, which in practice means bone marrow and the basal layer of your skin.
In pigmentation
B12 deficiency is associated with hyperpigmentation, most often on the knuckles and the palmar creases, and with premature greying. Both are documented and both reverse when B12 is restored, which is a useful reminder that this nutrient has visible consequences.
Our Amount
6 mcg In Every Serving
Our serving carries 6 mcg. Adult requirements sit around 2.4 mcg a day, so this is a comfortable multiple — deliberately, because B12 absorption is inefficient and declines with age.
B12 hands a methyl group to an enzyme that regenerates folate, and folate is what carries the carbon atoms DNA is written with. No working B12 means no working folate, and no working folate means the cell about to replace the one on your cheek never gets built. Skin divides harder than almost any tissue you own.
When People Fall Short
Deficiency is common and under-diagnosed, and it has two quite different causes. The first is dietary: vegans and strict vegetarians take in almost none unless they supplement or eat fortified foods. The second is absorption, which is the more common cause in older adults.
Absorbing B12 requires stomach acid to release it from food and intrinsic factor to carry it across the gut wall. Age reduces stomach acid. So do proton pump inhibitors taken long term, and metformin interferes further down the chain. Autoimmune loss of intrinsic factor causes pernicious anaemia.
Nerve symptoms — tingling in the hands and feet, unsteadiness, memory changes — can precede any change in the blood count, and can become permanent if left. This is a nutrient to test rather than guess about.
Where It Occurs In Food
| Source | Roughly | Notes |
|---|---|---|
| Clams | Over 80 mcg per 100 g | Extraordinarily rich |
| Liver | About 70 mcg per 75 g | One serving covers weeks |
| Salmon | About 4.9 mcg per 100 g | Reliable and ordinary |
| Beef | About 2.5 mcg per 100 g | Everyday coverage |
| Dairy and eggs | 0.5–1.4 mcg per serving | The vegetarian mainstay |
| Fortified plant milks | Varies by brand | The only reliable vegan route besides supplements |
The Ceiling, And The Cautions
No upper intake limit has been established. B12 is water soluble, absorption is self-limiting through the intrinsic factor route, and excess is excreted.
The genuine risk with B12 is the opposite one. High folate intake can correct the blood picture of a B12 deficiency while the nerve damage continues unnoticed, which is one of the reasons the two nutrients sit together on our panel. If you have nerve symptoms, ask for a B12 test rather than adding a supplement and hoping.
Answers
Vitamin B12 Questions
The questions we are asked about this nutrient specifically.
Is methylcobalamin better than cyanocobalamin?
It is the form used directly in the methylation reaction, so it needs no conversion. Cyanocobalamin is more stable and very well studied. Both raise blood levels; the practical difference is smaller than the marketing suggests.
I am vegan. Is 6 mcg enough?
It is a sensible daily contribution, but if you eat no animal products at all you should be managing B12 deliberately and testing occasionally rather than relying on a skin supplement to cover it.
Does B12 stop grey hair?
Greying caused by a documented B12 deficiency can improve when the deficiency is corrected. Ordinary age-related greying is genetic and no supplement reverses it.
Can B12 give me energy?
If you are deficient, correcting it can be transformative. If you are not, it does nothing, and the excess is excreted. Fatigue has many causes and most of them are not this one.