Actual quote from his book Notes on the State of Virginia:
Had not free enquiry been indulged, at the aera of the reformation, the corruptions of Christianity could not have been purged away. If it be restrained now, the present corruptions will be protected, and new ones encouraged. Was the government to prescribe to us our medicine and diet, our bodies would be in such keeping as our souls are now. Thus in France the emetic was once forbidden as a medicine, and the potatoe as an article of food.
emedic = medicine to cause vomiting.
Since at least 1997 the statement "Was the government to prescribe to us our medicine and diet, our bodies would be in such keeping as our souls are now" has been misquoted in paraphrased form as "If people let government decide what foods they eat and what medicines they take, their bodies will soon be in as sorry a state as are the souls of those who live under tyranny".