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Organic tomatoes have higher antioxidant value, suggests study

By Nathan Gray , 04-Jul-2012
Last updated on 04-Jul-2012 at 17:18 GMT2012-07-04T17:18:42Z

Organic tomatoes have higher antioxidant value, suggests study

Tomatoes grown by organic methods contain more phenolic compounds than those grown using commercial standards, say researchers.

The study – published in the Journal of Agricultural and Food Chemistry – analysed the phenolic profiles of Daniela tomatoes grown either using ‘conventional’ or organic methods, finding that those grown under organic conditions contained significantly higher levels of phenolic compounds than those grown conventionally.

“The nutrient composition of plants, including secondary plant metabolites, may be affected by different production systems, such as organic and conventional,” noted the researchers, led by senior author Rosa Lamuela from the University of Barcelona.

"Organic farming doesn't use nitrogenous fertilizers; as a result, plants respond by activating their own defence mechanisms, increasing the levels of all antioxidants," explained study lead Anna Vallverdú Queralt.

Organic vs Conventional: Controversial

The fundamental differences between organic and conventional agricultural systems are in fertilization strategy and soil fertility management, which in theory affect the nutrient composition in plants and provide healthier better tasting produce.

However, years of research investigating the nutrient content of plants grown using the two systems have generated largely contradictory results. A 2009 UK Food Standards Agency (FSA) review  investigating the nutritional content of organic and conventional produce sparked controversy after it concluded that there was no difference.

The FSA research concluded: “there is no evidence to support the selection of organically produced foodstuffs to increase the intake of specific nutrients or nutritionally relevant substances.”

However, a second review published by the French food agency AFSSA completely contradicted the findings of the FSA, concluding that “organic plant products contain more dry matter and minerals – such as iron and magnesium – and more antioxidant polyphenols like phenols and salicylic acid”.

Several smaller studies have since backed up the findings of the AFSSA review by reporting higher levels of certain nutrients in organically grown produce including strawberries .

Lamuela and her team have previously reported organic tomato juice  to be more nutritious than those grown in the standard commercial, and revealed that ketchup made from organic tomatoes contains higher levels of beneficial antioxidant compounds.

Study details

Using liquid chromatography coupled to mass spectrometry, the team identified 34 different phenolic compounds in tomatoes, before comparing them.

They analysed the profile differences for the content of flavonols (kaempferol-3-O-rutinoside, rutin, and quercetin), flavanones (naringenin and naringenin-7-O-glucoside), flavones (apigenin-7-O-glucoside), and hydroxycinnamic acids (ferulic, p-coumaric, caffeic, and chlorogenic acids.

Comparing the analyses of tomatoes from conventional and organic production systems demonstrated statistically higher levels (P < 0.05) of phenolic compounds in organic tomatoes.

Lamuela said 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. The researcher added that she would like to carry out a study with humans comparing organic and conventional tomato consumers.

Source: Journal of Agricultural and Food Chemistry
Volume 60, Issue 13, Pages 3373–3380, doi: 10.1021/jf204702f
“Evaluation of a Method To Characterize the Phenolic Profile of Organic and Conventional Tomatoes”
Authors: A. Vallverdú-Queralt, O. Jáuregui, A. Medina-Remón, R.M. Lamuela-Raventós