Most everyone today lives in a place where you can get just about any kind of produce year round. I doubt anyone can remember the last time they went to a store and did not see apples. Apples only grow 2 or 3 months out of the year so how are they in stores year round? If you have eaten an apple in the last 7 months, it was either shipped from new zeland or has been sitting in a warehouse being pumped full of gas to keep them from rotting. I am a chef by trade and have worked in the food industry more than half my life and I feel very strongly about eating in season. It is sad but simply eating fruits and vegetables is not enough anymore because you really have no clue what the life of that particular item has been. It used to be the farmers grow the food and send it to the market. People come to the market and buy the food. It takes two sentances to explain how food used to arrive if I tried to explain the complex process of our food system today it would take two pages. Farmers markets are by far the best place to get produce and you will only get what is in season. This option is not available for most people, at least not year round. I have attached a link to a chart of the seasonality of diffferent fruits and vegetables. If you buy in season you will get better products. They will taste better, be fresher and the nutritional content will be higher. If you are content with eating frozen processed food then you may ignore this but if you really care about what goes into your body it is worth taking a look.
http://www.azcentral.com/style/hfe/food/articles/2008/07/08/20080708inseason_cal-CR.html
Andrew