A cup of coffee, for instance, makes a very poor breakfast to start the day on; for although it gives you a comforting sense of having eaten something warm and satisfying, it contains very little real food, and soon leaves you feeling empty and tired; just as an engine would give out if you put a handful of shavings into its fire-box, and expected it to do four hours' work on them.
The most disturbing effects of tea and coffee upon the digestion are due to the tannin which they contain if boiled too long, especially in the case of tea.

This tannin, fortunately, will not dissolve in water except by prolonged boiling or steeping; so that if tea is made by pouring boiling water over the tea leaves and pouring it off again as soon as it has reached the desired strength and flavor, and coffee by being just brought to a boil and then not allowed to stand more than ten or fifteen minutes before use, no injurious amounts of tannin will be found in them.

Tea, made by prolonged stewing on the back of the stove, owes its bitter, puckery taste to tannin, and is better suited for tanning leather than for putting into the human stomach.
Boys and girls up to fifteen or sixteen years of age are much better off without tea, coffee, or cocoa; for they need no artificial stimulants to their appetites, while at the same time their nervous systems are more liable to injury from the harmful effects of over-stimulation.

If the beverages are taken at all, they should be taken very weak, and with plenty of milk and cream as well as sugar.
ALCOHOL How Alcohol is Made.

The most dangerous addition that man has ever made to the water which he drinks is alcohol.