Vitamin B12 is created by bacteria naturally found on plants and in soil, however modern conventional farming reduces this bacteria. It is still found in meat so you must supplement it if you are vegetarian or vegan.
I live with a healthy, active, woman of 62 who has been vegan for 30 years. She does it for Animal Rights. http://peta.org
The reason why governments and some specialists promote a carnivorous diet is that they are supporting a Big Money making industry. The Canada Health Guide is one such source of politically biased misinformation.
I am an organic vegetarian (grains, legumes, veggies, fruits, nuts, seeds, occaisional egg). It isn't difficult at all after the initial information intake.
I do it for my health, the animals, and the health of the planet: factory farms produce huge quantities of methane, are cess pools of human disease agents, promote genetically modified organisims, reduce bio diversity, and starve the poor(10 lbs grain equals one pound of beef)
I have also been good friends with animals and know they are emotional and intelligent. For me being nearly vegan has lifted a weight from my heart, my body, and is an important practice for world peace: www.earthsave.ca
It took a long time to start making different choices, I did enjoy eating animal products. Don't expect an overnight transformation, try being mindful and aware of your cravings.