From Scientific American,
In an article about how nitrates may actually be beneficial:
"The story of nitrate's positive side began ni 1994, when Jon Lundberg of the Karolinska Institute in Stockholm and Nigel Benjamin of Peninsula Medical School of Exeter, Englind, independently observed that the human stomach harbos large amounts of the gas nitric oxide (NO)."
Unfortunately, on further research I have found that laughing gas is nitrous oxide.
Good news! Nitric acid is found in automobile exhaust, mediates the erection of the penis, and aids in killing pathogens in the body. Amazing what you can find wandering around the web.