Vegans try to live, as much as possible, in a way that avoids exploiting and being cruel to animals. This means following a plant-based diet. Vegans do not eat animals or animal-based products like meat, fish, seafood, eggs, honey and dairy products such as cheese. For many vegans, living a committed vegan lifestyle means not wearing clothes made from animal skins and avoiding any products which have been tested on animals. 　　Vegans argue that suffering is caused in the production of these foods. For example, they say that, on some dairy farms，male calves(小牛) are killed because they are too expensive to keep, and cows are killed when they get older and produce less milk. As for honey, vegans say that bees make honey for bee, not for humans, and that bees’ health can suffer when humans take the honey from them. Vegans believe that the products they use and consume should be free from not just cruelty but any exploitation of animals. 　　The main reason for going vegan is probably that they believe animals and all other sentient(有感知能力的) beings should have the right to life and freedom. However, there are other reasons. Vegans argue that the production of meat and other animal products is very bad for the environment. They point out that a huge quantity of water is needed to grow grain to feed animals in the meat industry. The enormous amount of grain which the meat industry needs often leads to forests being cut down and habitats(栖息地) being lost. In contrast, much lower quantities of grain and water are needed to sustain a vegan diet. In addition, many vegans say that all the nutritious elements our bodies need are contained in a carefully planned vegan diet and that this type of diet helps prevent some diseases.