Lettuce most often grown as a leaf vegetable but sometimes for its stem and seeds is a good source of vitamin A and potassium as well as a minor source for several other vitamins and nutrients.
Another reason lettuce greatly benefits health is because of its antioxidants. Not all varieties of lettuce have the same antioxidant effect because the color of its leaves determines the speed at which its compounds act. That is why lettuces with green leaves have antioxidants that react more slowly while lettuces with red leavers have a faster effect.
The results of a study published in the Journal of Agricultural and Food Chemistry took a look at the compounds of three lettuce varieties: green leaf Batavia, semi-red leaf Marvel of Four Seasons and the red leaf Oak Leaf. The researchers using Electron Paramagnetic Resonance techniques observed the behavior of the kinetics of the compounds of each variety.
The researchers discovered:
- The green-leaf lettuce contains water soluble, antioxidant compounds that act at a slow and intermediate speed.
- The red-leaf lettuce has compounds with intermediate and rapid kinetics.
- The semi-red-leaf lettuce has three kinds of compounds, with a rapid, intermediate and slow speed.
Having determined the kinetics of the antioxidants, the research is currently continuing with the aim of achieving a nutraceutical improvement of these three varieties of lettuce. The research group is now trying to boost the effect of the specific compounds in each variety by subjecting the plants to short stresses. These compounds perform defense functions in plants. So if conditions that are not the normal ones are applied to them - such as watering them with salinated water, subjecting them to high lighting intensity or working with raised concentrations of CO2 - these defenses will become intensified and, as a result, the antioxidant qualities of the plants will be boosted.
"The fact that there are compounds that act at different speeds does not mean that some are better or worse than others, says lead researcher Usue Prez-Lpez of the Department of Plant Biology and Ecology of the UPV/EHU's Faculty of Science and Technology. f we eat foods that can generate free-radical activity, there will be some compounds that act to eliminate them more quickly. But at the same time, 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. What matters in this process is not to lose productivity, and that is why we apply short-intensity stresses. With excessive stress, we could reach a point in which plant growth is reduced, and we are not interested in achieving greater quality at the cost of a reduction in size. The aim is to maintain production and achieve greater quality in this production.