I do want to mention that you do also have to look out to get enough of : Omega 3, Calcium, Iodine, Iron, Selenium, Protein.
Takes a bit of work at the start to adapt but it's very doable, and it's not like Omnivores don't have comparable deficiencies from not eating enough plants and fruit. Not to mention other problems that come with eating animal products...
I only supplement with Omega 3, Vitamin D, B12, Iodine (although sometimes I go for wakame). Have been on a plant-based diet for around 4 years now, feeling healthy.