You probably know that vegetarian nutrition is considered very healthy. It's a well-known fact that vegetarians never suffer obesity, high blood-pressure, cholesterol sedimentation on vessel sides and many other diseases of circulatory and digestion systems, unlike people who eat a lot of meat and dairy products.
However vegetarians may face other problems, caused by lack of vital amino acids. Basically there are 25 amino acids necessary for human organism to function well, maintain good health and develop muscles, and only 8 ones (10 for children) out of this number cannot be synthesized by human body itself; 4 are unavailable from protein food.
As for strict vegetarian food, e.g. products of plant origin, it can only provide 3 vital amino acids out of 8; non-strict vegetarian nutrition that also includes dairy, eggs and seafood if diverse enough can provide all these acids plus has minimal negative effect any animal meat have.
Taking into consideration all these scientific facts