Declining Fruit & Veg Nutrient Composition

[Guest guest]

Wednesday, Feb. 18, 2009

Eating Your Veggies: Not As Good For You?

By M.J. Stephey

Declining Fruit and Vegetable Nutrient Composition: What Is the Evidence?

By Donald R. Davis

Journal of HortScience; February 2009, 5 pp.

The Gist:

If the economy isn't grim enough for you, just check out the February issue of

the Journal of HortScience, which contains a report on the sorry state of

American fruits and veggies. Apparently produce in the U.S. not only tastes

worse than it did in your grandparents' days, it also contains fewer nutrients —

at least according to Donald R. Davis, a former research associate with the

Biochemical Institute at the University of Texas, Austin. Davis claims the

average vegetable found in today's supermarket is anywhere from 5% to 40% lower

in minerals (including magnesium, iron, calcium and zinc) than those harvested

just 50 years ago. (Read about Americans' Incredible, Edible Front Lawns.)

Highlight Reel:

1. On the Difficulty of Comparing " Then " and " Now: " Davis is quick to note that

historical data can sometimes be misleading, if not altogether inaccurate. Take

early measurements of iron in foods: because scientists failed to sufficiently

remove clinging soil, iron levels appeared unusually high in certain vegetables

like spinach, (which gave rise to the myth that it contained exorbitant amounts

of the mineral — a myth further propagated by the popular cartoon character,

Popeye). Then again, good historical data provides the only real-world evidence

of changes in foods over time, and such data does exist — one farm in

Hertfordshire, England, for example, has archived its wheat samples since 1843.

2. On the So-Called " Dilution Effect: " Today's vegetables might be larger, but

if you think that means they contain more nutrients, you'd be wrong. Davis

writes that jumbo-sized produce contains more " dry matter " than anything else,

which dilutes mineral concentrations. In other words, when it comes to growing

food, less is more. Scientific papers have cited one of the first reports of

this effect, a 1981 study by W.M. Jarrell and R.B. Beverly in Advances in

Agronomy, more than 180 times since its publication, " suggesting that the effect

is widely regarded as common knowledge. " (See pictures of fruit.)

Less studied, though, is the " genetic dillution effect, " in which selective

breeding to increase crop yield has led to declines in protein, amino acids, and

as many as six minerals in one study of commercial broccoli grown in 1996 and

'97 in South Carolina. Because nearly 90% of dry matter is carbohydrates, " when

breeders select for high yield, they are, in effect, selecting mostly for high

carbohydrate with no assurance that dozens of other nutrients and thousands of

phytochemicals will all increase in proportion to yield. "

2. On the " Industrialization " of Agriculture: Thanks to the growing rise of

chemical fertilizers and pesticides, modern crops are being harvested faster

than ever before. But quick and early harvests mean the produce has less time to

absorb nutrients either from synthesis or the soil, and minerals like potassium

(the " K " in N-P-K fertilizers) often interfere with a plant's ability to take up

nutrients. Monoculture farming practices — another hallmark of the Big Ag

industry — have also led to soil-mineral depletion, which, in turn, affects the

nutrient content of crops.

The Lowdown:

If you're still not buying the whole " organic-is-better " argument, this study

might convince you otherwise. As Davis points out, more than three billion

people around the world suffer from malnourishment and yet, ironically, efforts

to increase food production have actually produced food that is less nourishing.

Fruits seem to be less affected by genetic and environmental dilution, but one

can't help but wonder how nutritionally bankrupt veggies can be avoided.

Supplementing them is problematic, too: don't look to vitamin pills, as recent

research indicates that those aren't very helpful either.

The Verdict: Skim

http://www.time.com/time/health/article/0,8599,1880145,00.html