Nature does not intend that man shall live by bread alone, nor by any one kind of food.

She indicates this by the varying tastes and longings that she gives him.

If his body needs one kind of constituents, his tastes lead him to desire the food that is richest in those constituents.

When he has taken as much as his system requires, the sense of satiety supervenes, and he "becomes tired" of that particular food.

If tastes are not perverted, but allowed a free but temperate exercise, they are the surest indicators of the way to preserve health and strength by a judicious selection of alimentation.
In this case Nature was protesting by a rebellion of the tastes against any further use of that species of food.