I was a vegetarian for 6 years, and I have been a vegan for 8 months. Contrary to popular belief, getting protein is easy as a vegan.
What I worry most about is B6, B12, and Omega 3-6-9 Fatty Acids, specifically, EPA, and DHA.
I eat foods fortified with B6, B12, and I take vitamins. Meat-eaters might moan that I have to take supplements, but believe it or not, most of the cattle and livestock you eat are also given B12 supplements. Why not just skip two middle-men (the animal and the butcher)?
Omega-3 ALA is found in chic peas and flax seed, but Omega-3 ALA conversion to Omega-3 EPA and Omega-3 DHA is only ~10%, but becomes more efficient the longer one is vegan.
Myths would say that fish is the best way to get these Omega 3-6-9 fatty acids, but where do you think the fish get their Omega 3s?
This is why I buy 100% Vegetarian (Vegan) Omega-3 from microalgae (Schizochytrium oil), which contains EPA and DHA for cardiovascular and cognitive health.
In case you didn’t know, the solution to 99% of problems is most definitely algae.