Mixing lettuce varieties could help provide protection against the chain reactions of free radicals, molecules that can cause cell damage and generate various diseases, suggests a study.

The findings, published in the Journal of Agricultural and Food Chemistry, said that mixing lettuce, one of the indispensable vegetables in the Mediterranean diet, could be a good idea as not all lettuce varieties have the same antioxidant effect.

The researchers from the University of the Basque Country (UPV/EHU) in Spain and the University of Pisa in Italy analysed the compounds of three lettuce varieties: the green-leaf 'Batavia', the semi-red-leaf 'Marvel of Four Seasons', and the red-leaf 'Oak Leaf'.

Using Electron Paramagnetic Resonance (EPR) techniques, they were able to observe the behaviour of the speed (kinetics) of the antioxidant compounds of each variety.

The results showed that the green-leaf lettuce contains water-soluble, antioxidant compounds that act at a slow and intermediate speed, the red-leaf one has compounds with intermediate and rapid kinetics, and the semi-red-leaf one has three kinds of compounds, with a rapid, intermediate and slow speed.

"The fact that there are compounds that act at different speeds does not mean that some are better or worse than others," said Usue Perez-Lopez, researcher at UPV/EHU.

It is also important that our bodies should acquire foods with antioxidants that have slower kinetics so that the latter will continue to act over a longer period of time.

"That is why people say that it is very interesting to mix different types of lettuce because they have different, complementary characteristics," Perez-Lopez added.

Free radicals harm our body by causing, in the best of cases, ageing and, in the worse, serious diseases.

Lettuce is rich in antioxidants, as it contains compounds like phenolic acids, flavonoids, anthocyanins, and vitamins A and C, among other things, the researchers said.