A century of breeding iceberg lettuce for higher yield per acre and durability in transit has also, inadvertently, dramatically lowered its nutrient contents. Add heavy spraying of pesticides and the result is a vegetable with the taste and nutritional value of crunchy, polluted water.
This occurrence is not isolated to iceberg lettuce. 'Better' breeds of wheat have less protein, and sturdier tomatoes have less vitamin C. For that matter, more beautiful roses have less scent than their plainer forebears.
At one time, this practice could have been defended, or at least forgiven, on the basis of ignorance. However, agribusinesses now knowingly sacrifice nutrition for the kind of qualities that benefit a supplier, rather than a consumer. Since, as one farming textbook put it, "the decision to eat is guided by the money available, tradition, and the taste of food, but generally not on the nutritional quality" (Ken Asubel, Seeds of Change, Harper Collins, 1994), suppliers can generally make this sacrifice without fear of reprisal. This, of course, is just one of many gaps in the principle of consumer sovereignty, which leave it ill-equipped to serve as a proxy for democracy.
See also: Enriched Flour.