First things first: vitamin B12 occurs in relevant amounts practically only in animal foods. That makes it the one nutrient where the question of supplementation on a purely plant-based diet is not really a question at all, but already answered.
Why B12 of all nutrients
Most vitamins can be covered well from plants. B12 cannot. It is produced by microorganisms and reaches meat, fish, eggs and dairy through the animal gut. Plant foods contain it only in traces or in forms the human body cannot use.
This is why professional bodies recommend permanent supplementation on a vegan diet. On a vegetarian diet it depends on how much milk and egg actually ends up on your plate.
What B12 does in the body
Vitamin B12 contributes to normal energy-yielding metabolism, to the normal functioning of the nervous system, to normal homocysteine metabolism, to normal psychological function, to normal red blood cell formation and to the normal function of the immune system, and it contributes to the reduction of tiredness and fatigue. It also has a role in the process of cell division.
Why supplements are dosed so high
The reference intake is 2.5 µg per day. Supplements still deliver 500 or 1,000 µg, which is two hundred to four hundred times that amount. It looks like overkill, but there is a factual reason for it.
The uptake of B12 in the small intestine runs through a transport route that only lets a limited amount through per single dose. Anything beyond that is taken up passively, and only to a very small percentage. To still arrive at a meaningful amount via this second route, the dose has to be correspondingly high. High B12 numbers are therefore not chest-thumping, they follow from the mechanics of uptake.
That also explains why lozenges are common: via the oral mucosa, part of it bypasses the small intestine and goes directly into the bloodstream.
Methylcobalamin, cyanocobalamin and the others
Labels list different forms. Cyanocobalamin is the most stable and the longest studied one, and the body has to convert it first. Methylcobalamin is one of the forms that are present in metabolism directly. Both serve their purpose, and the differences are often presented as bigger than they are.
Our Vitamin B12 Depot 1000 µg uses methylcobalamin. The recommended intake is half a lozenge per day, so 500 µg. One tin therefore lasts up to 480 days.
How to check your status
B12 is one of the few nutrients where measuring really pays off, because the body builds up a store and the status changes slowly. More informative than the plain B12 level in blood is the holotranscobalamin value or methylmalonic acid. That is a conversation for your family doctor, not for a search engine.
In short
- B12 comes practically only from animal sources. On a vegan diet, permanent supplementation is the consensus.
- The high dosages follow from the limited uptake per single dose, not from marketing.
- Lozenges additionally use the route via the oral mucosa.
- If you want clarity about your status, a measurement is worthwhile, ideally via holotranscobalamin.
Do not exceed the stated recommended daily intake. Food supplements are not a substitute for a balanced, varied diet and a healthy lifestyle.
