In pigs, heating or filtering cow's milk doesn't change how well vitamin B12 gets absorbed in the gut — it's the same whether the milk is raw, pasteurized, or microfiltered.

Pigs absorb way more vitamin B12 from cow's milk than from a lab-made version, and they don’t absorb the lab version at all — their bodies only seem to take in the natural kind.

Giving B12 shots to milk-making cows doesn’t make the milk any better at delivering B12 to pigs’ guts — the pigs absorb about the same amount either way.

When pigs eat a plant-based meal with synthetic B12 (cyanocobalamin), their bodies don't seem to absorb it — there's no measurable amount showing up in their gut system compared to a meal without it.

Your body can only absorb a little bit of vitamin B12 at a time—about as much as what’s in a single serving of meat or fish. If you eat or take way more than that in one meal, your body just can’t use the extra, so most of it goes to waste.