What does the Bible say about vegetarian diets? Is there any verse in Bible that says something about being a vegetarian or non-vegetarian? I know God set human beings above the other creatures, but what does it say about whether we can kill them?
There are a number of verses that talk about what you should or can eat and a few of them do concern vegetarian eating. There are a number of Christian sects that even have a "health message," where they prescribe a vegetarian diet. I think the most notable one is Seventh Day Adventists, but note that the diet is a suggestion in their mind, not Biblical law.

Starting from the beginning, there is a development of what God gives mankind to eat. In the garden, God first gives the fruit of the trees and any seed bearing plant (fruits).


  Then God said, “I give you every seed-bearing plant on the face of the whole earth and every tree that has fruit with seed in it. They will be yours for food. And to all the beasts of the earth and all the birds in the sky and all the creatures that move along the ground—everything that has the breath of life in it—I give every green plant for food.” And it was so.
  Genesis 1:29-30 (NIV)


When Creation was completed, God gave Adam any fruit he wanted as his food, and to all the other creatures, He gave any green plant. In Genesis 2:16-17 God gives Adam every tree in the Garden and forbids that Adam should eat from the Tree of Knowledge, but that is a theological/obedience issue rather than a practical, dietary issue.

During God's pronouncements of punishments for eating the forbidden fruit, Adam is told that his food will be plants in Genesis 3:18. It's a bit ambiguous, but we can assume that it means all plants, like the animals were first given.

After the fall we see an interesting development. The people became farmers and kept flocks.


  Now Abel kept flocks, and Cain worked the soil.
  Genesis 4:2 (NIV)


It also seems to have been permitted as well, that they should keep flocks, and, we assume, eat their meat, but that may be too hasty.

After Noah and his family survive the Flood, we see God allow animal flesh eating with only two prohibitions:


  Everything that lives and moves about will be food for you. Just as I gave you the green plants, I now give you everything. But you must not eat meat that has its lifeblood still in it.
  Genesis 9:3-4 (NIV)


Now God has given everything to eat, except blood and other people (that is in following verses and I left it out because you don't usually need to convince people that cannibalism is wrong).

This leaves a few questions about the previous verses. The first is did they (the righteous) actually eat meat before the Flood? We know they tended flocks, but they also sacrificed. It is possible that they only tended flocks for the sacrifice. The second question is when exactly did God give them the green plants? The earliest hint at this is after the fall in Genesis 3:18 and Genesis 4:2. God says plants will be your food, then Cain worked the soil later, which we assume means farming fruit and vegetables.

Some sects use the following verses and logic to support that vegetarian eating is better for you. Though that may be true, I think you would be hard pressed to say that the Bible commands a vegetarian diet, and I have never heard of a group that says it does, though, I do know that the SDA say it is encouraged.

There is another interesting story concerning food and vegetarian diets. Daniel 1 details a story where Daniel, a young man, was taken captive because he was intelligent, young, and handsome, and was given food from the royal table. Daniel saw this as an abomination, likely because the meat of that table included animals sacrificed to idols and might also have included blood. So Daniel asks his overlord to give him and the other servants only vegetables and water for 10 days and see if they are not healthier than the others.


  At the end of the ten days they looked healthier and better nourished than any of the young men who ate the royal food.
  Daniel 1:15 (NIV)


Some groups, like the SDA, point to this as factual and Biblical evidence that a vegetarian diet is better for you. Others say that it was the power of God that made them healthier because they wanted to avoid the royal table because it was defiled, not simply because it had meat on it; the objection was against meat that either had blood in it or was sacrificed to idol or both. They then develop ideas like a "Daniel fast," where you eat only vegetables and water for 10 days in an effort to increase your faith and the also tend to quote Mark 7:18-19, stating that no food can defile you. It's a bit of a red herring because Christians with the health message would agree.

Whatever any Christian decides, there is one verse that cannot be more clear on this subject:


  So whether you eat or drink or whatever you do, do it all for the glory of God.
  1 Corinthians 10:31 (NIV)