See How the Mid-Victorians Worked, Ate and Died.
"The crude average figures often used to depict the brevity of Victorian lives mislead because they include infant mortality, which was tragically high. If we strip out peri-natal mortality, however, and look at the life expectancy of those who survived the first five years, a very different picture emerges. Victorian contemporary sources reveal that life expectancy for adults in the mid-Victorian period was almost exactly what it is today.
From 1875 on and especially after 1885, rising imports of cheap food basics were increasingly affecting the food chain at home. Imported North American wheat and new milling techniques reduced the prices of white flour and bread. Tinned meat arrived from the Argentine, Australia and New Zealand, which was cheaper than either home-produced or refrigerated fresh meat also arriving from these sources. Canned fruit and condensed milk became widely available.
This expansion in the range of foods was advertised by most contemporaries, and by subsequent historians, as representing a significant ‘improvement’ in the working class diet. The reality was very different. These changes undoubtedly increased the variety and quantity of the working class diet, but its quality deteriorated markedly. The imported canned meats were fatty and usually ‘corned’ or salted. Cheaper sugar promoted a huge increase in sugar consumption in confectionery, now mass-produced for the first time, and in the new processed foods such as sugar-laden condensed milk, and canned fruits bathed in heavy syrup. The increased sugar consumption caused such damage to the nation’s teeth that by 1900 it was commonly noted that people could no longer chew tough foods and were unable to eat many vegetables, fruits and nuts . For all these reasons the late-Victorian diet actually damaged the health of the nation, and the health of the working classes in particular.
See also Who Lives Longest? (h/t to Melissa McEwen)