vegetables are deficient in b12, b6, protein, phosphorus, sodium, iron, manganese.
vegetarian diets are excellent for kidney health, heart health, liver health, and galbladder health. it reduces fat in the body, reduces cholesterol (note: some people with a certain condition get WORSE cholesterol on vegetarian diets but that's very rare), and may ward off most forms of cancer.
vegetarian diets, however, increase levels of oxalic acid, potasssium, and zinc. That wouldn't be a problem, except when you get too much of it (which is easy on a vegan diet), you greatly increase the risk of testicular/ovarian cancer, or other genitourinary conditions.
meat is actually especially important for women, who have problems maintaining iron, manganese, calcium, and protein in their bodies. men should actually eat less meat and dairy than women, though this is seldom the case.
an omnivorous diet is important for your health. it's not that vegans are more healthy than carnivores. actually they deteriorate just the same.
the key is to eat meat, but in small portions, and only lean meat or meat heavy in omega-3 fatty acids (like fish) to make up the difference that veggies don't compensate for.
we literally ARE omnivores and we are designed to eat meat, however our nutrition structure is generally geared more toward a slightly more vegetarian influence since we mostly enjoy a sedentary lifestyle.
anyway if you eat a lot of fast food or meat, you WILL experience a LARGE increase in your overall health by eating veggies and whole foods instead of processed ones, it's not rocket science. your body seeks natural food, because there's more nutrition there. but people need to understand that a lean piece of beef or a cut of salmon will do your body just as many wonders as a grapefruit or a piece of broccoli.