The Wealth of Nations by Part 1 Chapter 11 Page 52

rank of people in England who are fed with wheaten bread.

They neither work so well, nor look so well; and as there is not the same difference between the people of fashion in the two countries, experience would seem to show that the food of the common people in Scotland is not so suitable to the human constitution as that of their neighbours of the same rank in England. But it seems to be otherwise with potatoes. The chairmen, porters, and coalheavers in London, and those unfortunate women who live by prostitution, the strongest men and the most beautiful women perhaps in the British dominions, are said to be the greater part of them from the lowest rank of people in Ireland, who are generally fed with this root. No food can afford a more decisive proof of its nourishing quality, or of its being peculiarly suitable to the health of the human constitution.