Aside from their greater presumed safety – due to the lack of pesticide residues – people commonly assume that organic fruits and vegetables are healthier than conventional produce.
Prior studies comparing the antioxidant and nutrient content of foods grown organically or conventionally have produced mixed results … though organic produce has generally shown higher levels (see “Organic Crops' Nutrition Advantage”.)
Now, tomato-focused studies from Spain's University of Barcelona (UB) – and related studies from Poland – affirm the idea that organic vegetable and fruits contain higher levels of “antioxidant” polyphenol compounds than their conventional counterparts.
Polyphenols abound in tea, cocoa, berries, onions, and in many vegetables and fruits with proven human health benefits.
Diets rich in polyphenols are associated with the reduced risk of cardiovascular and degenerative diseases, and some forms of cancer.
Although they're commonly called “antioxidants”, polyphenols and carotenes don't appear to exert major, direct antioxidant effects in the body … just in test tubes.
Instead, the benefits that polyphenols and carotenes produce in people flow from their “nutrigenomic” influences on cellular gene switches, which boost the body's own antioxidant network and reduce inflammation.
Organic tomatoes beat conventional for antioxidant content
The UB's Natural Antioxidant Group, headed by Rosa M. Lamuela, previously proved that organic tomato juice and ketchup contained higher polyphenol levels than juice and ketchup made from conventionally grown tomatoes.
For the new study, her team compared a single tomato variety grown organically or conventionally.
The Spanish team identified 34 polyphenol compounds in the tomatoes … as well as lycopene and other carotenoids, and vitamin C.
And, compared with conventionally grown tomatoes, the organic tomatoes had higher levels of polyphenols, to a statistically significant extent (Vallverdú-Queralt A et al. 2012).
Meanwhile, in Poland, researchers raised a single tomato variety on several organic and conventional farms, over two growing seasons.
The Polish study also produced positive results, with the organic tomatoes producing higher levels of vitamin C and polyphenols, in comparison with the conventional fruits (Hallman 2012).
Lamuela plans to carry out a human study to compare the physiological and nutrigenomic effects of organic and conventional tomatoes.
Gazpacho affirmed as a good source of antioxidants
This research group also published this year a study to assess changes in individual polyphenol and carotenoid compounds of commercial gazpachos kept in the fridge.
Storage of gazpachos for three months only resulted in a slight decrease in their polyphenol and carotenoid content capacities.
“Gazpacho does not only contain polyphenols from tomato, but also polyphenols from onion, garlic, etc”, said Lamuela.
It seems plausible to presume that this gazpacho finding would apply to similar commercial salsa products.
Why do organic crops produce more polyphenols?
Differences between organic and conventional crops are linked to two reasons.
First, “over-fertilization” of conventionally grown plants with synthetic nitrogen results in lower levels of polyphenols.
Second, plants produce polyphenols to serve as chemical defenses against diseases and pests.
Conventional crops produce smaller amounts of polyphenols because, being protected by potent, broad-spectrum pesticides and fungicides, they face less stress from diseases and pests.
Conversely, organic farms don't use potent synthetic pesticides, so the crops grown on them face greater stress from microbes, fungi, and insects.
As Lamuela said, “The more stress plants suffer, the more polyphenols they produce” … which is a boon to human consumers of organic crops.
Hallmann E. The influence of organic and conventional cultivation systems on the nutritional value and content of bioactive compounds in selected tomato types. J Sci Food Agric. 2012 Feb 20. doi: 10.1002/jsfa.5617. [Epub ahead of print]
Vallverdú-Queralt A, Jáuregui O, Medina-Remón A, Lamuela-Raventós RM. Evaluation of a method to characterize the phenolic profile of organic and conventional tomatoes. J Agric Food Chem. 2012 Apr 4;60(13):3373-80. Epub 2012 Mar 26. DOI: 10.1021/jf204702f
Vallverdú-Queralt A, Arranz S, Casals-Ribes I, Lamuela-Raventós RM. Stability of the phenolic and carotenoid profile of gazpachos during storage. J Agric Food Chem. 2012 Feb 29;60(8):1981-8. Epub 2012 Feb 15.
Vallverdú-Queralt A, Medina-Remón A, Casals-Ribes I, Amat M, Lamuela-Raventós RM. A metabolomic approach differentiates between conventional and organic ketchups. J Agric Food Chem. 2011 Nov 9;59(21):11703-10. Epub 2011 Oct 11.
Vallverdú-Queralt A, Martínez-Huélamo M, Arranz-Martinez S, Miralles E, Lamuela-Raventós RM. Differences in the carotenoid content of ketchups and gazpachos through HPLC/ESI(Li(+) )-MS/MS correlated with their antioxidant capacity. J Sci Food Agric. 2012 Aug 15;92(10):2043-9. doi: 10.1002/jsfa.5598. Epub 2012 Jan 30.