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.

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.

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.

When you eat fish, sheep meat, or chicken, your body absorbs vitamin B12 from them at different rates—fish gives you about 42% of the B12, sheep meat gives you 56% to 89%, and chicken gives you 61% to 66%, so not all meats give you the same amount of this important vitamin.