It can be hard work being a vegetarian, and I have seen many who are suffering with poor health which can be related to their diets. Humans are evolved to eat an omnivorous diet, and vegetarians can sometimes miss out on key nutrients if they avoid meat and fish (and even more so if they are vegans or avoiding eggs).
The main thing I find that’s lacking is protein. It’s very easy to exist on bread, pasta, and rice with vegetables if you are a vegetarian. Vegetarian sources of protein are not that common in a northern European diet (think lentils, tofu, nuts, seeds) and so it doesn’t always come easily to vegetarians to include these foods. Eggs are a great source of protein, but not all vegetarians like eating eggs. I sometimes find myself recommending a protein supplement for vegetarians, particularly if there are health reasons indicating that they are low in protein. There are many different protein powders available, but I favour this one from Lamberts made of pea protein. This is totally vegetarian, and easily digestible.
The other thing that I find routinely lacking in a vegetarian diet is essential fat. People who eat fish are often showing symptoms of being low in essential fats (in particular, omega 3 fatty acids), so for vegetarians who eat no oily fish, the situation can be even worse. Sources of omega 3 fatty acids for vegetarians are mainly nuts and seeds, but in general, these foods do not form a significant part of most vegetarians’ diets so again a supplement might be useful. Flaxseed oil used as a salad dressing (it should never be heated) is a good way of getting some valuable omega 3 – Nutrigold’s Flaxseed Oil is great. Or if capsules are more convenient, Nutrigold also produce a capsule form of Flaxseed Oil.
And finally, vegetarians can often be low in zinc. Meat and seafoods contain zinc, and in fact oysters have the highest levels of zinc out of all foods. Brazil nuts are good vegetarian sources of zinc, as are pumpkin seeds and seaweed. If you choose to take a supplement to boost zinc levels, go for 15mg per day.