A new research conducted by the American scientists discovered that organically grown tomatoes may contain higher level of flavonoids, a class of plant secondary metabolites known especially for their antioxidant activity. Due to this effect, it is believed that flavonoids are good against cancer and heart diseases.

Alyson Mitchell from the University of California-Davis, and researchers from University of Minnesota have studied dried tomatoes samples in order to determine the levels of quercetin and kaempferol aglycones, two common flavonoids.

According to their findings organic tomatoes contained on average 79 and 97 per cent more flavonoids than conventionally grown tomatoes.

“People are not eating enough fruits and vegetables in the first place, so having higher levels of flavonoids is probably a good thing,” researcher Dr Alyson Mitchell said.

The plants are producing higher level of flavonoids as a defense mechanism that can be triggered by nutrient deficiency, such as lack of nitrogen in soil. In conventionally grown plants the inorganic nitrogen in conventional fertiliser is easily available.  

"This increase corresponds not only with increasing amounts of soil organic matter accumulating in organic plots but also with reduced manure application rates once soils in the organic systems had reached equilibrium levels of organic matter," concluded the researchers.

The conclusions of the study published in Journal of Agricultural and Food Chemistry have reignited the debate about the benefits of organically grown plants, especially since previous research has found no differences between organic and conventional crops such as wheat or carrots.

Speaking with The Times, Lord Krebs, former chairman of the UK's Food Standards Agency (FSA) and now an academic at Oxford, said that higher flavonoid levels do not necessarily mean that organic food is healthier.