Vitamin B12 is indeed absorbed differently depending on the source, but it is not only due to the type of food itself. The human body’s absorption of vitamin B12 is a complex process that involves several steps and can be affected by various factors.
I’ve always struggled with deficiencies. My impression is that vitamin B12 from animal-derived foods like meat, fish, eggs, and dairy products is well-absorbed by the body. Studies show that this happens due to the presence of a protein in the stomach called intrinsic factor which is essential for the absorption of B12.
The presence of other dietary components can also affect the absorption of vitamin B12. For instance, the vitamin is better absorbed in an acidic environment. So foods or conditions that decrease stomach acidity (such as antacids or atrophic gastritis) can reduce B12 absorption.
As for plant-based sources, most naturally occurring plant foods don’t contain B12 unless they’re fortified. Certain types of algae and fermented foods may contain B12, but the bioavailability of B12 in these foods is often less than that of animal-based foods, and the absorption rates can vary widely.
Fortified foods, like cereals, non-dairy milks, and nutritional yeast, can be a good source of B12 for vegetarians and vegans. The B12 in these products is usually in a form that’s easily absorbed, but the amount can vary depending on the specific product.
We human can also have variations in our ability to absorb B12 due to age, genetic factors, digestive system health, and other medical conditions. For example, older adults and people with certain gastrointestinal disorders like Crohn’s disease or celiac disease may absorb less B12 from foods.
While the food source of B12 can impact absorption, so too can the overall context of one’s diet, health status, and individual physiological factors. If you have specific concerns about B12 intake and absorption, you should consult with a healthcare provider or dietitian.