The latest research on diet and nutrition at the time of the Norman Conquest is summarised in an article on HeritageDaily and has used material from excavations in Oxford, including the castle. Modern scientific analysis of human and animal bones has yielded details of what was the diet of the people recorded in Domesday and the years following.
The results are interesting because they are not surprising. That is they pick up particular fluctuations - the Anglo Saxon Chronicle is replete with references to years that were the worst in memory in the 1070s and 1080s - yet show a society that basically could feed itself and was not showing malnutrition in conditions such as rickets. One change seems to be a greater consumption of pork, and maybe an increase in urban pig-keeping.
The article can be read at Norman Conquest of 1066 Did Little to Change People's Eating Habits - HeritageDaily - Archaeology News