(17-03-09) Plant Stress Boosts Nutrition

by Susanne Morrone


Reported that Alyson Mitchell, Ph.D. from the UC-Davis presented her team`s findings at the annual meeting of the American Advancement
of Science in Chicago Feb. 12-16, 2009. The team has been doing extensive research on the nutritional content in fruits and vegetables and the impacts from the way they are grown. Since many Americans tend to ignore the prolific data on the health benefits of these foods, the researchers set out to identify types of produce that offer an abundance per serving of vitamins, flavonoids, antioxidants and other micronutrients.

Mitchell stated field data shows that cultivar selection is an important but "oft overlooked" factor not only in crop selection but in nutrition as well. For example, under the same field conditions, white-fleshed nectarines can produce six times the quantity of total phenolic antioxidants as another.

While many cultivated old-style varieties are more nutritious, these crops are no longer grown commercially due to negative impacts from weather, transporting problems, and pests. Another problem, Mitchell states, is that the marketplace today rewards farmers for yield and disease resistance in their crops, not for how much beneficial
micronutrients a crop may contain.

The UC-Davis team wanted to ascertain the nutritional differences between organic and conventionally produced fruits and vegetables. Identical varieties of certified organically grown were compared to conventionally grown with its standard fertilizers and pesticide applications. Mitchell reported as aÂ? rule, organics far surpassed conventionally-grown for vitamins and beneficial micronutrients, such as quercetin and kaempferol.


According to Mitchell, the difference lies in metabolites. Plant nutrients are classified into two broad categories: primary metabolites (fats, carbs, amino acids and simple sugars) and secondary metabolites (phenolic acids, flavonoids, alkaloids and terpenoids). Normally, plants have a fairly balanced ratio of both primary and secondary metabolites with neither dominating. In conventionally-grown crops, primary metabolites are maximized. This is due to optimizing conventional practices and crop amendments.

Secondary metabolites, on the other hand, are defense compounds. They give the plant its protection-- essentially natural pesticides or sun screens. It makes sense, Mitchell said, that when plants aren`t stressed, they produce fewer of these compounds.
Organic crops tend to have more stress/damage from pests and weather. They respond by increasing production of the defensive secondary metabolites. The extra stress may result in less attractive produce, but the nutritional value of gram for gram can be superior.
"It`s time," Mitchell argued, "that we consumers - and the marketplace generally - find ways to reward farmers for the nutritional quality of their crops." Another benefit of the some secondary metabolites is that they break down into flavor compounds making organic crops tastier.

Alyson Mitchell is Associate Professor and Food Chemist at U.C.-Davis
as well as Vice-chair of the Functional Foods & Natural Products Subdivision of Agricultural and Food Chemistry Division of the American Chemical Society.


Source: ScienceNews (Feb. 13, 2009) AAAS: STRESS CAN MAKE PLANTS MORE NUTRITIOUS
Antioxidants and the Nutritional Quality of Organic Agriculture by
Alyson E. Mitchell, Ph.D., and Alexander W. Chassy mitchell.ucdavis.edu/Is%20Organic%20Better.pdf:
UC-Davis News and Information (Feb. 13, 2009) How
Organic and Conventional Farming Practices Impact Nutrients

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