smoking lsa isn't an option.
the impurities in dcm would be water, or other chlorinated hydrocarbons. they'll evap.
the favorable solvents for lsa extraction would be chloroform, dcm, or ethyl acetate.
I suspect a lot of the choices of "food-grade" solvents goes beyond preference, it's a fear of chemical toxicity. This is understandable, just become aware of exposure issues, and realize that carcinogenicity will most likely not occur from single (i.e. acute) exposure.
the human body is fairly robust, ingestion of trace amounts of solvents are relatively benign.
"Nothing is true, everything is permitted." ~ hassan i sabbah
"Experiments are the only means of attaining knowledge at our disposal. The rest is poetry, imagination." -Max Planck