Have no idea, really. Intrinsic factor is in the gut, so I don't think that's a factor when it comes to taking B12 sublingually, which is one reason they developed sublinguals, i.e., for those who couldn't absorb. The preferred way of getting B12 in fact is actually through your gut *because of* the intrinsic factor. We evolved absorbing b12 from eating meat, which no one takes sublingually, obviously. Sublingual absorption is a much poorer means of b12 absorbtion than through the gut, at least as long as you have intrinsic factor.