Produce has been losing vitamins and minerals over the past
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."
[Also to be factored in are the benefits of increased mortgage potential
when a factory farms replace non-factory farms that uses more land for
producing more nutritious foods (if grown organically).]
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
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
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
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
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
-- Donald R. Davis: "Trade-Offs in Agriculture and Nutrition,"
FoodTechnology, March 2005, Vol. 59, No. 3. A graph that illustrates
nutrient declines mentioned in the article is titled, "Trends in 43
Garden Crops USDA Data, 1950-1999" and can be found at
-- Virginia Worthington: "Nutritional Quality of Organic
VersusConventional Fruits, Vegetables and Grains." The Journal of
and Complementary Medicine, Vol. 7, No 2, 2001.
-- Anne-Marie Mayer: "Historical Changes in the Mineral Content
ofFruits and Vegetables," British Food Journal, 99/6, 1997.
-- The Swedish study, conducted by Marie E. Olsson, C.
StaffanAndersson, Stina Oredsson, Rakel H. Berglund and Karl-Erik
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, http://www.organic-center.org.