Vegetables and fruits stay alive after they have been picked, and you can extend their life further by ensuring they experience the full circadian cycle of night and day. They become richer in cancer-fighting antioxidants around the dawn when they increase their defences against aphids that would normally attack them while they were growing, say researchers from Rice University in California.
But produce that is stored away in the fridge or a dark shelf never have the sense of changing patterns during the day, and so don't produce the antioxidants.
The researchers discovered the phenomenon when they tested cabbages, spinach, lettuce, courgettes (zucchini), carrots, sweet potatoes and blueberries for their aphid-fighting chemicals-which happens to be when they are at their most nutritious for us.
(Source: Current Biology, 2013; doi: 10.1016/j.cub.2013.05.034).