Talk to old-timers, and they’ll often tell you that the tomatoes you find in supermarket produce sections don’t taste anything like the ones they had in their childhoods in the ’30s and ’40s.

Turns out, they’re probably not as nutritious, either.

In an article [PDF] published in the February 2009 issue of the HortScience Review, University of Texas researcher Donald R. Davis compiles evidence that points to declines in nutrition in vegetables and (to a lesser extent) fruits over the past few decades.

For example:

[T]hree recent studies of historical food composition data found apparent median declines of 5% to 40% or more in some minerals in groups of vegetables and perhaps fruits; one study also evaluated vitamins and protein with similar results.

He points to another study in which researchers planted low- and high-yielding varieties of broccoli and grain side-by-side. The high-yielding varieties showed less protein and minerals.

The principle seems to be that when plants are nudged to produce as much as possible — whether through lots of synthetic fertilizers and pesticides or through selective breeding — they deliver fewer nutrients. It evidently isn’t just the flavor that’s become diluted in those bland supermarket tomatoes.

This is a fascinating insight. We should reflect that for at least 50 years, the best-funded agricultural researchers are the ones work to maximize yield — that is, gross output per acre. Even now, the Bill & Melinda Gates Foundation is expending hundreds of millions of dollars in an effort to increase yields in Africa.

Rather than isolate and fetishize yield, perhaps ag researchers should learn to take a whole-systems approach: study how communities can develop robust food systems that build healthy soil and produce nutritious food.

(It should also be noted that last year the Organic Center compiled peer-reviewed studies finding that organically grown produce tends to deliver significantly higher nutrient levels than conventional.)