Healthy soil and sustainable growing

[Jerome Rigot <rigot.3@osu.edu>]

Organic fruits and vegetables work harder for their
nutrients

Produce has been losing vitamins and minerals over the past
half-century
http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2006/03/25/HOG3BHSDPG1.DTL
Deborah K. Rich, Special to The Chronicle
Saturday, March 25, 2006

The fruits and vegetables that our parents ate when they were growing
up
were more nutritious than the ones we'll serve our children tonight.
On
average, the produce we grow in the United States has lower levels
of
several vitamins and minerals today than it did 50 to 60 years ago.
By
growing or buying and eating organic produce, however, we can make up
much
of the difference. Organically grown fruits and vegetables are proving
to
have higher levels of antioxidants, vitamins and minerals than their
conventionally grown counterparts.

Donald R. Davis, a research associate with the Biochemical Institute at
the
University of Texas, Austin, recently analyzed data gathered by the USDA
in
1950 and 1999 on the nutrient content of 43 fruit and vegetable crops.
He
found that six out of 13 nutrients had declined in these crops over
the
50-year period (the seven other nutrients showed no significant,
reliable
changes). Three minerals, phosphorous, iron and calcium, declined between
9
percent and 16 percent. Protein declined 6 percent. Riboflavin declined
38
percent and ascorbic acid (a precursor of vitamin C) declined 15
percent.

A study of the mineral content of fruits and vegetables grown in
Britain
between 1930 and 1980 shows similar decreases in nutrient density.
The
British study found significantly lower levels of calcium,
magnesium,
copper and sodium in vegetables, and of magnesium, iron, copper and
potassium in fruit. The report concludes that the declines indicate
"that a
nutritional problem associated with the quality of food has developed
over
those 50 years."

The decline in our produce's nutritional value corresponds to the period
of
increasing industrialization of our farming systems. As we have
substituted
chemical fertilizers, pesticides and monoculture farming for the
natural
cycling of nutrients and on-farm biodiversity, we have lessened the
nutritional value of our produce. Integrated well-established
organic
farming systems can counter the decline.

Good science comparing the nutritional value of organic and
conventional
foods is accumulating rapidly. It isn't uncommon for researchers to
find
that the higher nutrient levels in organic produce completely offset
the
declines Davis found in conventional produce. "What all our data
shows,"
says Charles Benbrook, chief scientist at the Organic Center and a
former
executive director of the Board on Agriculture of the National Academy
of
Sciences, "is that whenever there's been a valid comparison
between
conventional and organic, organic is virtually never lower than
conventional and, in a significant number of cases, it's higher.
Sometimes
it's significantly higher in several important nutrients."

For example, Virginia Worthington, a clinical nutritionist who earned
her
doctorate in nutrition at Johns Hopkins, published a review in 2001 of
41
studies comparing the nutritional value of organic and conventional
produce. After tallying the data across all the studies, Worthington
concluded that organic produce had on average 27 percent more vitamin
C,
21.1 percent more iron, 29.3 percent more magnesium and 13.6 percent
more
phosphorous than conventional produce.

Benbrook released a review in 2005 of the research comparing
antioxidant
levels in conventional and organic foods. In humans, antioxidants
reduce
damage to cells and DNA from free radicals (molecules generated by
metabolic processes within the body), and thereby promote
cardiovascular
health, inhibit the reproduction of cancerous cells, slow the aging
process
in the brain and nervous systems, and lessen the risk and/or severity
of
Alzheimer's, Parkinson's and Huntington's diseases. Benbrook found that
in
85 percent of the comparable data points, produce from organic farms
had
higher levels of antioxidants than did produce from conventional farms.
On
average, antioxidant levels in organic produce were 30 percent
higher.

Earlier this year, a Swedish team of scientists demonstrated that
extracts
from organically grown strawberries slowed the proliferation of colon
and
breast cancer cells to a significantly greater degree than extracts
from
conventional strawberries did. The levels of all the antioxidants
analyzed
by the team were higher in the organic strawberries than in the
conventional.

"As someone that has been involved with science and science policy
for my
whole life," says Benbrook, "I think the scientific case has
been made for
organic produce. The case has been made firmly enough so that it is
appropriate and, indeed, irresponsible at this point not to tell
consumers
straight up that choosing organic fruits and vegetables probably
delivers
nutritional benefits because of the higher levels of antioxidants
and
vitamins and minerals."

The decline in nutrients

Our push for higher yields per acre and cheaper food is largely to
blame
for the decline in nutrient levels in conventional produce. With
irrigation
and fertilization we can get more pounds per acre, but often not
without
sacrificing nutrients per pound produced. This "dilution
effect" on
nutrient density was widely observed by agricultural scientists even 20
to
30 years ago. The use of hybrids selected for high yields has
probably
compounded the trade-off between yield and nutrients. Davis writes,
"Modern
crops that grow larger and faster are not necessarily able to
acquire
nutrients at the same, faster rate, whether by synthesis or by
acquisition
from the soil."

In addition to pushing a plant to grow big fast, heavy fertilization
can
interfere with a plant's ability to synthesize vitamin C. A plant
will
increase protein production and reduce carbohydrate production when
it
absorbs an abundance of nitrogen. "Because vitamin C is made
from
carbohydrates, the synthesis of vitamin C is reduced," writes
Worthington.

Use of potassium fertilizers (potassium is the "K" in N-P-K
fertilizers)
can reduce the phosphorous content of some plants. For the plant to
absorb
phosphorous, it must have adequate amounts of magnesium. But when
potassium
is added to soil, plants absorb less magnesium, and, indirectly,
less
phosphorus as well.

Organic farmers do not use synthetic formulations of fertilizers, and
this
restriction is part of the reason organic produce has relatively
higher
nutrient values. Organic farmers feed their crops only indirectly.
Instead
of plying plants with nitrogen, phosphorous and potassium in readily
dissolved and absorbed powders and solutions, they fertilize their crops
by
adding organic matter to the soil in the form of composts, cover crops
and
manures. The organic matter feeds microorganisms in the soil that, in
the
process of eating and living and dying, recycle the nutrients embedded
in
the organic matter. The microbes slowly release not only nitrogen,
phosphorous and potassium but also a host of other nutrients in
ratios
difficult to replicate with synthetic fertilizers.

The large populations of microorganisms that typically inhabit
organically
managed fields also produce substances that combine with minerals in
the
soil and make them more available to plants, a function that can be
especially important for iron absorption. Iron is usually present in
soil,
but it is often in an unavailable form.

The relatively larger root-balls of organic plants are another
reason
organically grown plants can absorb a wider variety of nutrients
than
chemically fertilized plants can. Because organic plants don't have
macronutrients spoon-fed to them, they grow larger root systems out
of
necessity. Roots on organic plants have to range farther to access
sufficient nitrogen, phosphorous and potassium. In the process, they
come
into contact with more trace minerals and micronutrients than the
smaller
root-balls of conventional plants do. "When plants are growing, they
sense
how big a root system they have to produce to draw from the soil the
nutrients and moisture they need to grow and reach maturity and
reproduce,"
says Benbrook. "On a conventional farm where there are high levels
of
fertilizer nutrients in the soil, along with lots of water, there is
little
incentive for roots to penetrate far."

Making healthful choices

The role that antioxidants play in plant health probably also
contributes
to the higher antioxidant levels found in organic produce. Many
antioxidants help a plant resist diseases, deter pests and recover
from
insect damage. Because organically grown plants do not
"benefit" from the
protection of pesticides, they must be able to muster their own
defenses
and therefore produce high levels of antioxidants.

By providing plants with more balanced nutrition and by triggering
production of higher levels of antioxidants, organic farming systems
yield
fruits and vegetables that are, on average, more nutrient dense than
conventional produce. We can maximize the nutritional benefits of
eating
fruits and vegetables by choosing organic.

"For the average consumer that's looking for a way to tilt their
odds in
favor of healthy development and graceful aging for themselves and
for
their families, the single most important thing they can do is eat
more
fruits and vegetables and less added fat, sugar and highly processed
foods," says Benbrook. "The second most important thing for
them to do is
to seek out organic fruits and vegetables known to be high in vitamins
and
antioxidants."
Foods rated "very high" and "high" in
antioxidants

VERY HIGH

Blueberry, wild; artichoke, cooked; black plums; broccoli raab;
blackberry;
strawberry; blueberry, cultivated; cabbage, red; raspberry; apple
('Red
Delicious'); apple ('Granny Smith'); sweet cherry; bean, red kidney;
navel
orange; prune; bean, pinto; pear ('Red Anjou'); grape, red; potato,
russet;
raisin

HIGH

Asparagus, raw; lettuce, red leaf; asparagus, cooked; beet;
grapefruit,
red; peach; pepper, yellow; tangerine; onion, yellow, cooked;
apricot;
grape, green; pineapple; potato, white; black-eyed pea; almond

Source: The Organic Center
Resources

-- Donald R. Davis: "Trade-Offs in Agriculture and Nutrition,"
Food
Technology, March 2005, Vol. 59, No. 3. A graph that illustrates the
nutrient declines mentioned in the article is titled, "Trends in 43
Garden
Crops USDA Data, 1950-1999" and can be found at
www.organic-center.org/reportfiles/Davis_ppt.pdf.

-- Virginia Worthington: "Nutritional Quality of Organic Versus
Conventional Fruits, Vegetables and Grains." The Journal of
Alternative and
Complementary Medicine, Vol. 7, No 2, 2001.

-- Anne-Marie Mayer: "Historical Changes in the Mineral Content of
Fruits
and Vegetables," British Food Journal, 99/6, 1997.

-- The Swedish study, conducted by Marie E. Olsson, C. Staffan
Andersson,
Stina Oredsson, Rakel H. Berglund and Karl-Erik Gustavsson, is
"Antioxidant
Levels and Inhibition of Cancer Cell Proliferation in Vitro by
Extracts
>From Organically and Conventionally Cultivated Strawberries,"
Journal of
Agricultural and Food Chemistry, American Chemical Society, published
on
the Web, Jan. 21, 2006.

-- The Organic Center,

www.organic-center.org.

-- D.K.R.

Deborah K. Rich is a freelance writer and olive rancher in Monterey.
E-mail
her at home@sfchronicle.com.