The time and distance that separates you from the sources of supermarket food takes a toll on nutrition, too. Large scale growers shipping nationally have to choose vegetable varieties that stand all that handling, even if it means they have to give something. And most of the healthy vitamins and mineral components in fresh produce begin to decline the moment of harvest. The longer the wait, the less there is left. Even organic crops — though they start out better — suffer from the centralized, long distance shipping system. Some of the crops highest in anti-oxidants such as beta-carotene are kale and winter squashes, both of which are relatively easy to grow.