HUMAN LUMINESCENCE

 Defined(meta-){Of higher order or level}

Defined(metamorphosis or transfuguration){A complete change of physical form or substance especially as by magic or witchcraft}

Defined(substance){The essential part of anything; the most vital part.}

Metahumans is something you hear in superhero movies. I thus use it as a starting point. 

Permit me to use the analogy of carbon. When I say: "pure carbon" what comes to mind is probably "carbon black." Science however knows that "Diamond" is also pure carbon. The difference being in the structural arrangement of the carbon atoms. While Diamond is highly valued, carbon black is not.

Delving a little into physics(optics): We know that for a substance to emit light, it has to be excited i.a  move to a higher level, a meta-state. Human beings who are spiritually fluorescent(diamond) are on a higher level than those who are non-fluorescent(carbon black).

There are different levels of human meta-states. According to one publication, a former occult grandmaster(avatar), the lowest state of human existence is known as "maya". 

Some people don't know what food is thus, they have never left this lowest level of human existence. People are not plants. So, feeding on what plant can process as food means you're not eating. To attain enough excitation that results in spiritual fluorescence nonetheless, requires more spiritual & physical exercise than just eating.

Who knows; there might yet still be another level of existence, a meta-state or a manifestation i.a BIOLUMINESCENCE.