Only humans and birds have color vision and it is believed that this evolved in humans to permit the selection of colorful fruits and vegetables from the green background of ancient jungles on the African plains. The plant colors absorb light and act as antioxidants to protect the plant from ultraviolet radiation as they use sunlight to produce energy for their survival through photosynthesis. If you have ever failed to water a house plant, you will notice blackened edges of the leaves. This happens because the antioxidant defenses in the plant’s leaves lose function. This is the same reason that dead leaves turn brown as their antioxidant defenses no longer work leading to the oxidation of the leaves which makes them turn brown.
We evolved on plants and when we eat these colorful compounds that are protective in plants, they act as antioxidants in our bodies as wells as having some other direct effects on cells making them Phytonutrients”. Different chemical structures associated with different colors can carry out specific functions in our bodies. For example, lutein found in spinach and avocados (green group) is concentrated in the optic nerve and in the brain maintaining vision and cognition, respectively. Lycopene associated with red frutis such as the tomato and watermelon concentrate in the prostate gland. Getting seven portions of 100 grams of each of the color groups is easy to do and contributes only about 500 Calories to the diet while providing lots of vitamins, minerals, fiber, water, and phytonutrients.
David Heber and Susan Bowerman What Color Is Your Diet? (Harper-Collins, 2001) available in paperback from Amazon.Com and selected booksellers