Lettuce color determines antioxidant speed: green-leaf has slower acting (but lasts longer) antioxidant compounds compared to red-leaf.

FTA:

Antioxidants provide long-term protection against the chain reactions of free radical processes, in other words, of the molecules that are capable of causing cell damage and generating various diseases. 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.