Secret Defense

Secret Defense

Plants contain a secret defense system. When stressed by insects, plants produce higher levels polyphenolic compounds, which are natural pesticides. And these compounds just happen to be potent antioxidants. But when chemical pesticides are used on crops, extra protection isn’t needed, so fewer polyphenolics develop and antioxidant content is depleted.

This is just one of the arguments in support of going to the extra trouble and expense to purchase organically grown foods. And a new study bears this out.

A level growing field

To compare the nutritional value of food grown organically with food grown using conventional techniques (chemical pesticides, herbicides, and fertilizers), researchers at the University of California-Davis harvested kiwifruits that were grown using these two different methods.

STUDY PROFILE

• The kiwis were grown at the same time on the same farm in Marysville, California
• Both crops were grown in the same soil type, under the same environmental conditions, and were harvested at the same stage of maturity
• Researchers assessed physical characteristics of the fruit, as well as content of compounds associated with flavor and nutrition
• The conventionally grown kiwifruit was firmer and had a lighter green color compared to organically grown
• The organically grown kiwifruit had less flesh area and thicker skin
• Sugars and organic acids were the same in kiwifruits from both growing methods

Writing in the Journal of the Science of Food and Agriculture, the authors of the study offered this comment about nutritional value: “All the main mineral constituents were more concentrated in organic kiwifruits, which also had higher levels of ascorbic acid and total phenol content, resulting in a higher antioxidant activity.”

Power of the polyphenolic

The results of the Marysville study are similar to the results of two organic food trials I told you about in previous e-Alerts.

In a 2003 issue of the Journal of Agricultural and Food Chemistry, another University of California-Davis team reported on a study in which they assessed the nutritional differences of marionberries (a type of blackberry), strawberries, and corn raised by three different methods: Organically – no pesticides, herbicides, or fertilizers were used

Sustainably – no pesticides or herbicides were used, but crops were treated with artificial fertilizers

Conventionally – chemical pesticides, herbicides, and fertilizer were used

Results showed that the plants grown organically and sustainably had far more polyphenolic content (and antioxidant activity) than those grown conventionally.

And in 2002, British researchers evaluated 35 different brands of vegetable soup, both organic and non-organic. They found that on average, the organic brands contained nearly six times as much salicylic acid, a natural anti-inflammatory agent. One of the organic soups contained nearly 50 times the concentration of salicylic acid as the typical non-organic soup.

Earlier work by the same British team found that eating salicylic-rich foods elevates blood concentrations of the acid, which is known to fight certain types of cancer as well as plaque build up in the arteries. Like polyphenolics, salicylic acid is produced by plants as a natural defense mechanism against insects.

Choosing organic over conventionally raised foods is largely an act of faith – especially when it comes to processed foods. But if you can find a reliable source of fresh whole foods that are grown by rigorous organic standards, count yourself lucky.

Sources:
“A Comparative Study of Composition and Postharvest Performance of Organically and Conventionally Grown Kiwifruits” Journal of the Science of Food Agriculture, Published online ahead of print 3/27/07, interscience.wiley.com