Well actually bananas don't glow, they just emit small amounts of beta radiation. The radiation has to collide with something which scintillates or produces light in order to glow. Phosphorous is one of these substances and is what is used in the glow tubes.

The bananas contain large amounts of Potassium which (when found in large enough amounts) always contains a small amount of Potassium 40, which is mildly radioactive. Do a web search for Potassium 40.

Aparently table salt substitute is radioactive, I haven't tried it. Some older orange glazed pottery contains Uranium which gives it it's color and is therefore radioactive.