|
Declining Fruit and Vegetable Nutrient Composition: What Is the Evidence
|
Douglas W. Morrison
|
Mar 21, 2009 07:50 PST
|
Declining Fruit and Vegetable Nutrient Composition: What Is the
Evidence?
Hello Folks
Here is an interesting review forwarded by my friend Carlisle Shoemaker
-- thanks, Carlisle!
Cheers,
Doug
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.
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." 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."
3. 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.
|
|
 |
|
