The many factors in our modern lifestyle that block the complicated uptake pathways of this important nutrient — from nutrient deficiencies to exposure to toxins to factors in processed foods that cause
reduced stomach acid, autoimmune disease and enzyme disruption — make it difficult to obtain sufficient quantities from our normal diet; and since vitamin B12 in supplements is produced in exactly the same way as B12 in nature, that is, by
bacterial fermentation, the danger of high doses in most cases is negligible.