M.H.
You should take a multivitamin anyway. I've been on and off the vegetarian wagon for years, and really what it all boiled down to for me is that it's not about not eating meat or badly farmed or exploited animals, but it's a bigger issue. Eating locally produced food, including meats, cheeses, milks, honeys, vegetables, fruits... is more responsible. If you live in an area with great farms, farmers markets, and good whole groceries, eating locally produced organic foods is the best thing you can do. It's not necessarily more expensive either. We participate with a CSA (community supported agriculture) where we pay up front to get locally farmed goods. Ours only offers veggies and fruits, but have started offering yogurt, eggs, herbs, and flowers too. We only get veggies (a huge box that has 6 items a week for about $325 for the season, seems like thats about $8 a week), but we can get local eggs from a lot of places, and we buy a lot of local goods from the farmer's market on the weekend.
Some CSA's (not all are organic, so check) offer everything, meats, grains, butters, milks, fruits, veggies, maple syrup, I mean everything, but could cost $1000-$2000 per year (I still think that's worth it), and people can supplement what they can't get by buying domestically sourced organic items from their favorite grocery.
Factory farms are awful, and vegetarian and vegan issues are very political. The facts would outrage anyone. But the truth is, not all vegetarians are skinny (its all the cheese and salt everyone adds!) and not all vegans are healthy. Too much soy can make you sick. I, and many female (and male) friends, know from personal experience. You CAN eat too much of it.
The mainstream movement these days is towards buying and eating local goods, eating LOCAL organic. We need to be saving ourselves, saving fuel, and stimulating the local economy the right way. Not eating organic raspberries from Chile and broccoli from Venezuela and tomatoes from Mexico just because it happens to be cheaper. We have organic farmers in our own backyards who are growing wonderful foods and raising responsible farms with fairly treated animals right here within miles of where we live in many cases.
See what you can find out about eating local and organic. Maybe you can add some of that to your paper as an argument on more sustainable options than just going vegetarian or vegan.
The movie Food, Inc. was pretty eye opening, we got that on netflix.
Meat isn't the only hot political issue. The way veggies are grown on big farms can shock you too. Try "The Future of Food" and "King Corn". That all leads to genetically engineered stuff, bred for toughness in shipping, speed of growth, and resistance to herbicides.
You might also enjoy "Food Fight" which is a documentary about Alice Waters efforts to promote local, organic and sustainable agriculture, and "No Impact Man: The Documentary" (This is from a very popular book).