I heard that overcooked meat causes cancer.

This article supplies some details and useful information on that: http://www.vegetarian-nutrition.info/updates/vegetarian_diets_health_benefits.php +5

very healthy for them cows and sheep,lol

none at all ,you got to watch your health like a hawk if you dont eat meat

That's not really the correct question. As a 'vegetarian' or 'vegan' diet can mean many things. Donuts & beer could be my vegan diet. If you're saying a recommended vegan diet, that is based on wholefoods, plenty of fruit & vegetables, then there is research that backs up a reduction in a few cancers, possibly a link to lower obesity & type 2 diabetes. Unlike the person above who seems to think it's plain sailing eating a meat-based diet, but you 'need to watch your diet like a hawk' when it contains no meat, that isn't the case...well actually ANY diet should be reviewed now again, goals checked & results observed, you should also be keeping an eye on your essential fatty acid intake, lowering your junk food intake etc. A more concrete answer can be found for if you look at 'health' to include living conditions on the planet as these are hugely reduced by animal rearing, transport etc. Water is polluted, the shear mass of resources wasted on their production is enormous & the green house gases produced out do even that of all the transport in the world! So in terms of adversely affecting your childrens lives (or your old age possibly) then it's very hard to justify meat eating.