Study shows higher levels of phenolic compounds in organic tomatoes

Jul 4 2012

Study conducted at the University of Barcelona shows that organic tomatoes contain higher levels of phenolic compounds than conventional tomatoes. Phenolic compounds are organic molecules found in many vegetables with proven human health benefits. The UB's Natural Antioxidant Group, headed by lecturer Rosa M. Lamuela, had previously proved that organic tomato juice and ketchup contain higher polyphenol content than juice and ketchup made from conventionally grown tomatoes.

Lamuela points out that during the production process of ketchup and juice, there are lower levels of polyphenols; therefore it was necessary to verify that the differences observed in previous studies had their origin in the tomatoes themselves and not in the technology used during the production process. As lecturer Lamuela states, "it must be verified with raw material".

Polyphenols —natural antioxidants of plant origin— are considered to be of great nutritional interest because its consumption is associated with the prevention of cardiovascular and degenerative diseases, and some forms of cancer. The team behind the study has analysed a variety of tomato called Daniela and has determined its phenolic profile by using liquid chromatography coupled to mass spectrometry. With this method, the research group of the UB could identify 34 different phenolic compounds in tomatoes. According to Rosa M. Lamuela, "the benefit of taking polyphenols through foods is that they contain a wide variety of such molecules, which are increased". This would be more beneficial to health than the intake of supplements. Tomatoes also contain lycopene and other carotenoids, and vitamin C. Hence, according to Lamuela, "they contain many beneficial compounds".

Organic or conventional crops?

Differences between organic and conventional tomatoes can be explained by the manure used in both cases. "Organic farming doesn't use nitrogenous fertilizers; as a result, plants respond by activating their own defence mechanisms, increasing the levels of all antioxidants", explains the first author of the article, Anna Vallverdú Queralt. "The more stress plants suffer, the more polyphenols they produce", points out lecturer Lamuela. Numerous scientific investigations show that the consumption of these antioxidants has numerous health benefits. Researchers claim that more studies of clinical evidence are still needed to be able to state that organic products are truly better for our health than conventional ones. Lamuela would like to carry out a study with humans comparing organic and conventional tomato consumers.

Also participating in this research, published in the Journal of Agricultural and Food Chemistry, are researchers Olga Jáuregui, from the UB's Scientific and Technological Centres (CCiTUB), and Alexander Medina Remón, who, together with Rosa M. Lamuela and Anna Vallverdú Queralt, are from the UB's Department of Nutrition and Bromatology, from the Reference Network on Food Technology of the Government of Catalonia (XaRTA) and from the Institute for Research on Nutrition and Food Safety (INSA-UB). This research group is also affiliated to the Spanish Biomedical Research Centre in Physiopathology of Obesity and Nutrition (CIBERobn) and RETICS networks, from Carlos III Health Institute.

Gazpacho, a good source of antioxidants

This research group, specialised in natural antioxidants, has also published this year a study to assess changes in individual phenolic and carotenoid compounds of commercial gazpachos kept in the fridge. This research, also published in the Journal of Agricultural and Food Chemistry, shows that the storage of gazpachos for three months results in a slight decrease in their polyphenol and carotenoid content capacities. Therefore, commercial gazpachos are also a good source of healthy products. "Gazpacho does not only contain polyphenols from tomato, but also polyphenols from onion, garlic, etc., being a more complex product in terms of phenolic compounds", claims Rosa M. Lamuela. Also participating in the study are Sara Arranz, from the Hospital Clínic (UB-IDIBAPS), and Isidre Casals Ribes, from CCiTUB.