Can vitamin A turn back the clock on breast cancer?

A derivative of vitamin A, known as retinoic acid, found abundantly in sweet potato and carrots, helps turn pre-cancer cells back to normal healthy breast cells, which may help explain why some clinical studies have been unable to see a benefit of vitamin A on cancer: the vitamin doesn’t appear to change the course of full-blown cancer, only pre-cancerous cells, and only works at a very narrow dose.