Not to upset the vegetarians, but it's difficult to get every nutrient you need without the real deal: a big, juicy, shank of dead animal.
A lot of vegetarians are intelligent people, I get why they are doing it, even though everything we digest is broken down into six basic things: protein, fat, carbohydrates, minerals, vitamins, and water. Everything else is indigestible and eliminated as waste.
However, just because you're intelligent, doesn't mean you have the common sense to follow through. After Steve Jobs was diagnosed with pancreatic cancer, he spent nine months trying to diet the cancer away, subsisting entirely on steamed vegetables, fruit, and acupuncture. By the time he sought proper medical treatment, the aggressive cancer had spread to his liver. One unanswered question I will always have is if Jobs had immediately gotten treatment for the ailment that ultimately claimed him, would he have lived longer? The only thing I am reasonably certain of is that mushy broccoli won't cure consumption. Even a genius is capable of magical thinking, the reality distortion field finally failed, and we are all poorer for it.