Some people are "flexitarians" and eat a semi-vegetarian diet, consuming meat in small quantities. Then there's the vegan diet, which excludes meat, poultry, fish, eggs, dairy products and foods that contain these products. There is such variation in the dietary restrictions of vegetarianism that the number of beneficial dietary combinations seems incalculable.
So what's the best choice to make here?
One of the strongest pro-omnivore arguments is that vitamin B12 doesn't occur in plants naturally. This doesn't mean we must eat meat though, and we certainly don't need the wealth of fast food helping to fuel the slaughterhouse industry. Many proponents of vegetarianism and veganism will explain it is possible for everyone to thrive without meat if they supplement their diets with alternative sources of B12 and fat. But some still experience health problems only after beginning a vegan diet, even with adequate supplements. And there are reports of athletes trying and then quitting a vegan diet for different reasons, including muscle cramps and stiffness, constant hunger and low energy.
And to confuse matters further, new research shows that a vegetarian diet increases mental health issues.
According to Psychology Today, a new German study shows that vegetarians are more likely to be afflicted by depressive, anxiety, somatoform, dysmorphic and eating disorders, and the stricter the vegetarian's diet, the more likely the affliction becomes.
All that being said, science has shown that our brains certainly wouldn't have developed to be so intellectually human if we hadn't consumed meat.
But do we need meat? Sources differ widely in opinion, but the only way to know if a vegetarian diet will benefit you is by assessing your personal health. Then, you can amend your diet to meet your specific nutritional needs. If you're interested in reading about dietary problems in the real world and how people try to solve them, you can read personal narratives from vegetarians, ex-vegetarians, ex-rawists and others who have had to seriously rethink their "ideal" diet on beyondvegetarianism.com.