Who is Iduna?
Iduna is one of the Aesir Gods, the deities of the sky realm of Asgard. She is almost always shown as a youthful maiden, sometimes delicate and beautiful, sometimes sturdy and hard-working. In spite of the emphasis in myth on her youth and beauty, she has a very strong work ethic. She cares for the sacred orchard of Asgard, growing all the fruit for the Aesir - including the special golden apples that give those Gods their eternal youth and immortality. Iduna is a working goddess as well as a deity of health and rejuvenation, and these things are linked. She honestly believes that physical labor - especially working the earth - is the second-best thing that you can do for your health. The first thing, of course, is proper nourishment. Iduna is one of the Gods of agriculture and healthy food; she is the only such deity who is one of the Aesir.
She is married to Bragi, the skald god of poetry, music and eloquence. Various mythic figures have attempted to steal her in days past, coveting her gift of the golden apples of youth. In each case, she was recovered and no harm was done. Like her husband, she is a peacemaker rather than a proponent of war.
Iduna can be called upon for any health issue, as well as for getting one's body back in shape, getting over food issues, getting more out of one's diet, easing the transfer to healthy food instead of junk, and of course for blessing anyone with an orchard or fruit trees.
For more in-depth information on this goddess, read Galina Krasskova's article on Iduna.