Vegans, keep an eye out on iron, protein, vitamin D, vitamin B12 and omega-3 fatty acids. Iron deficiency may lead to anemia. Vegans must replenish vitamin B12. If you are in doubt, consult an expert!
A good veg-based diet must be varied, since it is variety itself that provides us with all kinds of nutrients. In order to avoid anemia we must keep an eye on having sufficient levels of iron. There is also the risk of protein deficiency, as meat-eaters get protein primarily from meat; there is also the issue of vitamin B12, which is contained primarily in animal-based foods. Apart from that, one must also ensure having enough calcium, vitamin D and omega-3 fatty acids.