Extreme weather boosts soy antioxidants

Lead plant physiologist Steven Britz of the ARS Food Components and Health
Laboratory, part of the Beltsville Human Nutrition Research Center in
Beltsville, Md., collaborated on the study with William Kenworthy with the
University of Maryland in College Park.

The researchers found that
weather and climate are significant factors affecting soybean seed tocopherol
content. Tocopherols are a family of antioxidants that protect biological
membranes. Among this family, alpha-tocopherol is the active form of vitamin E
in humans.

Soybean seeds are a major source of vegetable oil in the U.S.
diet, and consequently a major contributor to dietary tocopherol intake. The
daily Recommended Dietary Allowance for vitamin E for men and women aged 14 and
older is 15 milligrams. But more than 50 percent of American adults do not get
adequate amounts of vitamin E, according to experts.

For the study, the
researchers analyzed the content of tocopherols in soybean seeds grown at
several locations in Maryland between 1999 and 2002. Weather was relatively
normal between 1999 and 2001, but extreme drought and warmer temperatures
characterized 2002.

Since soybeans mature at different rates, the
researchers examined up to 18 soybean lines representing different maturity
groups. There were small but significant increases in the proportion of
alpha-tocopherol in beans from the same genetic line grown in warmer,
full-season Eastern Shore locations compared to beans that matured under
slightly cooler conditions.

But under extreme drought conditions in 2002,
early maturing lines had as much as a 3.5-fold increase in relative
alpha-tocopherol content, compared to the other years during which rainfall was
adequate. The field studies showed how nutritional properties of crops can be
dramatically affected by weather and potentially by global environmental change,
according to the authors.

The research was reported recently in the
Journal of the American Oil Chemists’ Society.