There was a time when I was very much into nutrition and I always heard that our soil is not what it used to be. You used to be able to get a ton of nutrients from the soil so that the potatoes and corn you pulled out of the ground would already be rich in nutrients just from the dirt.

In this way vegetarians were able to actually get the B vitamins that they need. Nowadays they have to take pills in order to get those vitamins and that's most likely because the soil is not rich in nutrients anymore.