After the Tomato Scare
Now that the tomato scare is over, people can go back to buying one of summer’s perennially favorite crops. The question is, should shoppers buy organic or conventionally grown tomatoes? If they’re looking for the more nutritious tomatoes, the organic ones might be the way to go. A farming experiment at the University of California, Davis – as reported by NPR’s Allison Aubrey in May – found that organic tomatoes are more nutritious. The experiment, which is part of a 100-year study, compared organic and conventionally grown tomatoes in neighboring plots. The organic tomatoes had almost double the concentration of two flavonoids associated with strong antioxidant activity: quercetin and kaempferol.
Was the difference due to how the tomatoes were grown? The jury is still out on that, but the experiment suggests that it was. A possible scientific explanation for why the type of fertilizer used – natural or chemical – may have influenced the nutritional value of the tomatoes is tied to how quickly they absorbed nitrogen.
The conventionally grown tomatoes quickly absorbed the nitrogen in the commercial fertilizer they received, while the organic tomatoes had to work harder to absorb the nitrogen in theirs. The organic tomatoes used natural fertilizer made of manure and composted cover crops. The slower absorption of the nitrogen played a role in the formation of flavonoids in the organic tomatoes.
That said, researchers weren’t 100 percent sure that the difference was due to how the tomatoes were grown. Other possible explanations could have been differences in soil types, moisture and irrigation, and variety of tomatoes.