What are the side-effects of Maca?

Maca (Lepidium meyenii, and other Lepidium species) is a food and medicinal plant originally used by the indigenous peoples of Peru and Bolivia, who collect both the leaves and the root.  Although marketed as an aphrodisiac and energy enhancer, it's traditional use suggests that it was rather more important as a food, the leaves used as a fresh vegetable, and the root or hypocotyl used as a flour in baking.  Given its traditional importance as a food, rather than as a medicine, claims for its medicinal efficacy should be viewed with a little skepticism - especially when consumed in small amounts: remember, we are talking about a medicinal food here.  There are many anecdotal reports of its medicinal efficacy, but much of these reports come third hand from companies selling it as a supplement.  A survey of the medical literature suggests a benefit on exercise performance and sexual function.  Maca does contain goitrogens that some have speculated may aggravate pre-existing hypothyroid states, but this isn't a commonly observed symptom associated with use.  As it is a food, Maca is reasonably safe and can be expected to produce very few side-effects.  With trying anything new however, make sure to try a small amount first to see how your respond, just a few hundred milligrams at a time.  If no response is noted after a couple days, feel free to bump up the dose to medicinal levels.  Although drug-herb interactions aren't well-established, it is probably a good idea to consult with a practitioner before you take Maca if you are also taking pharmaceutical drugs.