So practically every food that comes upon our tables has some kind of real food value, or it wouldn't appear there.
The most careful study and analysis have shown that almost every known food has some peculiar advantage, such as digestibility, or cheapness, or pleasant taste as flavoring for other more nutritious, but less interesting, foods.

But some foods have much higher degrees of nutritiousness or digestibility or wholesomeness than others; so that our problem is to pick out from a number of foods that "taste good" to us, those which are the most nutritious, the most digestible, and the most wholesome, and to see that we get plenty of them.

It is not that certain foods, or classes of food, are "good," and should be eaten to the exclusion of all others; nor that certain foods, or classes of food, are "bad," and should be excluded from our tables entirely; but that certain foods are more nutritious, or more wholesome, than others; and that it is best to see that we get plenty of the former before indulging our appetites upon the latter.
Beware of Tainted Food.

The most dangerous fault that any food can have is that it shall be tainted, or spoiled, or smell bad.

Spoiling, or tainting, means that the food has become infected by some germs of putrefaction, generally _bacteria_ or _moulds_ (see chapter XXVI).