The general public has been aware of protein, carbohydrates, fats, vitamins and minerals from edible plants for a very long time. The unique mixture of phytochemicals in specific edible plants may be of equal importance, from the perspective of health and nutrition. A biomedical researcher describes one of the tools used by nutritionists to help decipher the web of interactions in which these phytochemicals are involved, once ingested by human beings.
Trees for Life Journal (2005) Vol 1:4
Plant foods as sources of pro-vitamin A: application of a stable isotope approach to determine vitamin A activity.