Which foods are classified as "nightshades," and is it true that foods from this group can potentially contain problematic substances?

Nightshades - all belonging to a scientific family of plants called Solanaceae - include several thousand species of flowering plants, and most of these plants are not edible as food. At the very same time, however, there are a good number of ...

from The World's Healthiest Foods http://ift.tt/2eg9IOv