Organic tomato boosted at UCD

In another tantalizing suggestion that organic produce may be more nutritious, UC Davis researchers have found that tomatoes grown organically in a campus test field packed an extra punch.

The organic tomatoes were richer in two types a flavonoids, compounds believed partly responsible for lower rates of cardiovascular disease and some cancers in people who eat lots of fruits and vegetables.

The study, published online in June by the Journal of Agricultural and Food Chemistry, adds to a sometimes conflicting body of knowledge about whether organic foods provide significant nutritional benefits.

"There's a lot of confusion," said Alyson Mitchell, a professor of food chemistry and toxicology at the University of California, Davis. "For every study that shows there's a difference, there's another that shows there isn't."

The flavonoid study conducted by Mitchell and six co-authors takes one of the longest looks so far at organic farming's impact.

The research team relied on dried tomatoes that had been kept as part of broader, unrelated research comparing organic, conventional and intermediate growing methods over more than 10 years.

During that time, the primary flavonoid in the Western diet, quercetin, and its close relative kaempferol both increased in organic tomatoes grown in the campus test plot.

What might have happened, Mitchell theorized, is that when cover crops and compost were used in organic farming year after year, they gradually increased the organic matter and overall fertility of the soil.

That meant growers didn't need to use as much compost to keep nitrogen levels high. And without that extra boost of growth-promoting nitrogen, plants seemed to devote more energy to producing flavonoids.

The findings don't necessarily mean that all organic tomatoes would contain more flavonoids, Mitchell stressed, because soils and growing methods on different farms could vary tremendously.

On top of that, scientists don't actually know how flavonoids work in our bodies or how much of them people need for optimum health.

Still, "Americans are not eating enough fruits and vegetables in the first place, so having higher levels (of flavonoids) is probably a good thing," Mitchell said.

About the writer:

• The Bee's Carrie Peyton Dahlberg can be reached at (916) 321-1086 or cpeytondahlberg@sacbee.com.