Salicylic Acid, Heavy Metal Content in Organic vs. Conventional Tomatoes

Background and methodology 
Organic farming is a production technique that imposes major restrictions on the use of fertilizers, pesticides, feed additives and veterinary drugs. For this reason consumers perceive organic foods to be healthier. The content of health-promoting molecules such as ascorbic acid, b-carotene, lycopene and salicylic acid (a type of plant hormone) are important aspects of the nutritional quality of organic foods. This study examined health-promoting substances and the heavy metal content of tomatoes grown using conventional, integrated pest management (IPM), and organic farming techniques. Moisture was determined by drying, crude protein by the Kjeldhal method and ashes by incineration at 5500 C. Ergosterol, ascorbic acid, b-carotene, lycopene and salicylic acid were determined by HPLC. The levels of heavy metals were measured by atomic absorption spectroscopy.

Compared to crops grown using conventional and IPM methods, organic tomatoes contained more salicylic acid but less vitamin C and lycopene. Organic tomatoes also had higher Cadmium (Cd) and lead (Pb) levels but a lower copper content. The detected levels of contaminants (Cd and Pb) were found to be markedly lower than the maximum limits allowed by law (EU Regulation 1881/2006). Copper is considered to be essential to human health (U.S. Recommended Daily Allowance, 0.9 mg/day for adults) but may be harmful if taken in excessive amounts. The organic produce had slightly higher protein content than their conventionally cultivated counterparts, but the difference was minimal and consequently the nutritive significance was poor. The higher salicylate content supports the notion that organic foods are more wholesome, however, the lower lycopene and ascorbic acid levels of organic tomatoes are not to be regarded as positive. No residues of pesticides and ergosterol were detected in organic tomatoes. The findings show that farming techniques may have an impact on tomatoes quality.


Rossi, F., Godani, F., Bertuzzi, T., Trevisan, M., Ferrari, F., and Gatti, S. (2008). Health-promoting substances and heavy metal content in tomatoes grown with different farming techniques. European Journal of Nutrition, 46, 266-272. Available on-line at: