Cum Grano Salis

Cum Grano Salis is a science fiction novella by Randal Garrett, first published in 1959, under the pen-name David Gordon.

'Just because a man can do something others can't does not, unfortunately, mean he knows how to do it. One man could eat the native fruit and live... but how?'

An exploratory expedition's food is destroyed in a freak accident, and the native fruits of the planet are mysteriously poisonous. Every Earth creature that eats them, dies; except MacNeil. He gets fat while everyone else starves.