Congratulations on going vegetarian!
There are no nutrients in meat that are not also available from vegetarian or even vegan sources. If you are lacto-ovo vegetarian, you have nothing to worry about. Stay away from junk food, eat a variety of vegetarian food, and you'll be fine.
If you decide to go vegan, you have to be a little careful, but it's not a big deal. For vegans, the four food groups are: grains, legumes, fruits, and all other vegetables. If you eat regularly from all four groups, then your only remaining concern is vitamin B12. Most omnivores get it from meat, but it is not an animal product; it is a bacterial product. (Cows don't make B12. They get it in their diet from eating grass that they have
[email protected] on.) A vitamin B12 supplement is prudent if you are a vegan, since we tend to be fussy about cleaning our food, which removes the natural B12.
The nutrients that omnivores fret about (protein and calcium) when their friends or family go vegetarian or vegan are simply non-issues. If you are not starving, and if you are eating a sensible variety of foods (i.e. you are not trying to live on sugar alone for example) then you are getting enough protein. Protein deficciency is rare.
People worry about calcium for vegans. This is an artificial concern created by the dairy industry. They want us to think that milk is the only source of calcium. It isn't. Where does the cow get the calcium to put into the milk? From eating grass. Eat your veggies and avoid getting too much protein, and your calcium will be fine. (Yes, there is such a thing as protein excess. It causes calcium to leach out of your bones. The more milk you drink, the more protein you get, and the more dietary calcium you need. A recipe for financial success if you are a dairy marketer.)
I have been a vegetarian for 31 years, and a vegan for 18. I follow the above guidelines and don't worry. My health and fitness are above average.