The vivid colours in fruits and vegetables are due to the presence of a myriad of plant derived chemicals (phytonutrients) that protect the plant tissues from pests and environmental damage. Many of these chemicals are biologically active in humans, meaning that they are absorbed and enter the blood, and then interact with our cells, causing changes to occur. Some of the most important groups of these chemicals include the flavonoids, the carotenoids, the stilbenes and the terpenes. Many chemicals from these groups are found in edible plants consumed by humans and have been shown to be beneficial to the health when part of the diet.
However, the effects of these chemicals shows variation, and different groups and classes within groups show different but overlapping health benefits. Because the different colours of fruits and vegetables results primarily from them containing different combinations of these chemicals, it makes sense to eat a wide variety of different coloured fruits and vegetables to make sure that a wide range of these chemicals is present in the blood at any one time. The chemicals may also possess synergistic activity, and so the more variation that is present in the diet, the stronger the health benefits may be. Each day a rainbow of colours should therefore be consumed from the wide selection of fruits and vegetables available to us.