Organic fruit is grown in the absence of conventional pesticides, and this may increase the susceptibility of the fruit to disease and damage by pest. Although there is no real consensus on the matter, this is thought to reduce crop yields. This generally accounts for the higher cost of organically farmed produce. However, the increased exposure of organic fruits to pests during growth may increase the flavonoid content of the fruit and thus provide a superior product. This is because flavonoids are produced in plants as parts of a defence against pests, and those fruits with a higher exposure to pests have more flavonoids. Because flavonoids are known to be bioavailable in humans and confer protection from disease, the increased cost of organic fruit may be justified by the improved flavonoid content. It is certainly justified by the lack of conventional pesticides, none of which have ever been tested for safety in combination with other conventional pesticides. This is problematic because it is thought that they act synergistically when combined.