The present invention relates to functional foods comprising DAO and their use for the prevention or treatment of diseases or pathological conditions associated with high levels of histamine in blood, in particular for the prevention or treatment of migraine, chronic fatigue, fibromyalgia, spondylitis and pain caused by muscle contractures.

The present invention relates to functional foods comprising DAO and their use for the prevention or treatment of diseases or pathological conditions associated with high levels of histamine in blood, in particular for the prevention or treatment of migraine, chronic fatigue, fibromyalgia, spondylitis and pain caused by muscle contractures.

The present invention relates to functional foods comprising DAO and their use for the prevention or treatment of diseases or pathological conditions associated with high levels of histamine in blood, in particular for the prevention or treatment of migraine, chronic fatigue, fibromyalgia, spondylitis and pain caused by muscle contractures.

The gene encoding N-methylputrescine oxidase (MPO) and constructs comprising such DNA are provided, including methods of regulating MPO expression independently or with other alkaloid biosynthesis genes to modulate alkaloid production in plants and host cells. MPO genes or fragments thereof are useful for reducing pyrrolidine or tropane alkaloid production in plants, for increasing pyrrolidine or tropane alkaloid production in plants, and for producing an MPO enzyme in host cells.