Do I Need Vitamins to Supplement My Vegan Diet?

As a pregnant vegan (and parenting a vegan toddler), I have been told to be very careful about supplementing to make up for ‘deficiencies’ in the vegan diet. Vitamin B12 is a big one, since it doesn’t really occur in plant-based foods but is present in animal products. So we’re careful about that. I’ve also been told by my doctor to take (annoyingly expensive) omega-3 supplements. I don’t believe that does anything, given what I’ve read of studies on them, but I do it anyway. Unfortunately, choosing to live without animal products means living with the paranoia that I may do some long-lasting damage to me and my family, based on the intensity of advice I receive about vitamins.
—Anonymous

See my post linked at the top for the omega-3 supplements, which are equivalent to fish oil and which do not do much. If they help your paranoia, that’s good, though!

But: I flag this here as a clear example of a place where you do need vitamins to address a particular deficiency in diet. A vegan diet needs B12 supplementation because, as you say, it is not available in plant-based foods. Vegan pregnant women are also at higher risk for iron deficiency, since, again, plant-based foods provide less iron.

So: yes to B12 and possibly iron. Omegas, not so much, according to the data.

(Noting here: vegetarian diets likely do not need these supplements, since eggs and dairy products contain those nutrients.)