We decided to ask USDA ourselves, so we contacted the head of the USDA Agricultural Research Service, whose job it is to track the vitamins in food, among other things. Mr. Edward B. Knipling responded to our inquiry with a restatement of Ms. Johnson's letter to Organic Gardening magazine. So we pressed for a better answer. Already the National Academy of Sciences is telling us our vegetables don't have as many vitamins as they're supposed to. So far, no answer from the agency.
Vegetables are a major source of nutrition.
Without them, humans miss out on important vitamins, minerals and phytonutrients. If they are also disappearing, the extent is unknown. Kant AK, et al. 1990. Vitamin C status and mortality in US adults. Loria CM, et al.