Healthy Eating? Salad
Salad used to be something we ate only in the summer months. Worldwide food distribution now means that we have salad available all year round and one of the most popular forms appears to be ready washed and bagged salad leaves.
The salad leaves and vegetables are flown in and transported to packing houses. The salad is then cut or separated into individual leaves by hand, washed in chlorine, dried and sorted, packed into pillows of plastic in which the normal levels of oxygen and carbon dioxide have been altered.
One study, carried out in 2002, tested the levels of several nutrients (including Vitamin C) in the blood of people who had eaten fresh lettuce and those who had eaten the bagged/prepared type (both from the same source). Those who had eaten the fresh lettuce showed an increase in antioxidant levels in their blood, those who had eaten the lettuce stored in bags for 3 days showed no increase.
I assume one still gets some roughage from the bagged salad but it would seem that vitamins and minerals are in short supply. Fresh unprocessed lettuce is healthier (and cheaper).
Reference
Serafinie Mauro; Bugianesi Rossana; Salucci Monica; Azzini Elena; Raguzzini Anna; Maiani Giuseppe
Effect of acute ingestion of fresh and stored lettuce (Lactuca sativa) on plasma total antioxidant capacity and antioxidant levels in human subjects.
The British Journal of Nutrition 2002;88(6):615-23.