No. It’s not a health issue and does not indicate a loss of nutrients. Still, most people find brown lettuce unappealing and will want to cut off the discolored parts.
Browning usually results from oxidation caused by exposure to air when the leaves have been bruised or cut. Another cause is “tipburn,” which occurs in the field because of climate or soil conditions. Exposure to the ripening chemical ethylene (produced naturally by most fruits, but also used commercially as a ripening agent) can produce browning as well.
Bacteria and fungi can also cause browning, but these are not a health hazard, according to Dr. Tim Hartz, a crop specialist at the University of California, Davis. Lettuce and other produce can harbour harmful bacteria, of course, but these do not cause browning.
Select lettuce that looks fresh (not wilted), since it will taste better and last longer. To reduce browning at home, keep lettuce in the coolest part of the refrigerator, away from high-ethylene-producing fruits (such as apples, pears, peaches, bananas, tomatoes and melon), and keep it dry.
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