Many did not survive toi adulthood including those that lied in the comparative fresher air of rural England. That included all classes of children. If you are specifically asking about children of the poorer classes, which included the low paid agricultural labourers, dock labourers, industrial manufacturing workers etc, then they existed on a meagre unhealthy diet in an unhealthy environment that was not the choice of their families, as there was little choice to be made. Many children at a very youn age were admitted to the workhouses, where they were able to have a meagre slightly less unhealthy diet until they were old enough to be sent to work or be apprenticed out to an employer as a live in servant.
There were a growing number of charities and reformers who saw the plight of poor and orphaned children and tried to make a difference, check out the work ot Dr Barnardo:
http://www.hiddenlive...articles/poverty.html
http://www.guardian.c...entity.patrickbarkham
http://www.museumoflo...victorianchildren.htm
http://www.stockindex...section=keywordsearch
11:43 Tue 25th Jan 2011