The thing is that few people lack intrinsic factor.

Some research suggests that lack of intrinsic factor may result from many years of B12 deficiency.

What causes many people to be low on B12 is the use of antacids, which reduce stomach acid. Acid is needed to freed B12 from the protein in food.

I think that basically healthy people can benefit from a lot of things, whereas people who are really sick need more intensive help.