What it is
Vitamin B12 has authorised claims: it contributes to normal energy metabolism, normal nervous system function, normal red blood cell formation, normal homocysteine metabolism, normal psychological function and the reduction of tiredness and fatigue.
But "tiredness" is a symptom of many things. B12 serves those with a deficiency, and the deficiency is confirmed with a blood test, not with a trial capsule.
What it does
It is needed to make red blood cells and maintain nerves:
- It is only found in animal-origin foods, which is why vegan diets need a supply.
- Absorption depends on a stomach protein, intrinsic factor.
- Metformin and gastric acid drugs can lower its absorption over the years.
At the counter
When to recommend it
- A vegan diet without fortified foods
- Older people, and anyone on metformin or antacids for many years, with a blood test
- The hour and the meal do not change what it does
When not to
- Without a blood test in someone with neurological symptoms: tingling, loss of balance or memory. That is a reason to consult
- As a "tonic" for tiredness without other causes ruled out
- Cyanocobalamin in anyone with hereditary Leber optic neuropathy
Warnings
- Important NEUROLOGICAL SYMPTOMS (tingling, loss of balance, memory): need a consultation and a blood test; a supplement can delay the diagnosis.
- Caution PERNICIOUS ANAEMIA: without intrinsic factor oral is not enough in many cases and the doctor decides.
- Caution No claim promises energy to anyone without a deficiency.
- Worth knowing Methylcobalamin has not been shown superior to cyanocobalamin; price is not an argument.
Pharmacokinetics
- Absorption
- Via intrinsic factor; a small part passes without it at high oral doses.
- Distribution
- Liver reserve lasting years.
- Metabolism
- Converted into the active forms.
- Elimination
- Excess in urine.
Cyanocobalamin and methylcobalamin
| Aspect | Cyanocobalamin | Methylcobalamin |
|---|---|---|
| Stability | Very stable and best studied | Less stable |
| Price | Lower | Higher |
| Proven superiority | The reference | Not proven |
| Warning | Avoid in Leber | No such restriction |
Apart from the Leber warning, the cheap form serves just as well.
Self-assessment
Three questions. When you check your answers you will see the explanation for each one.
-
Neurological symptoms need assessment before a supplement.
-
B12 is found in animal foods.
-
Superiority has not been shown.
Training content. It does not replace the summary of product characteristics or clinical judgement.