Meaning: With a healthy dose of skepticism, suspicion, and caution.
Example: Dave has been known to stretch the truth a bit. Take what he says with a grain of salt.
Origin: Salt is now an inexpensive and readily available commodity. But it was once very valuable due to its high demand as a food preservative and relative scarcity.
Salt was thought to have healing properties and to be an antidote to poisons. To take (eat or drink) something "with a grain of salt" was to practice preventive medicine. One would do this if they were suspicious that the food might be poisonous or may cause illness.
