From the results of chemical analysis fruits appear to be closely comparable in their composition to the familiar vegetables such as the tubers and roots. They all contain much water, and varying amounts of sugars, and are relatively insignificant as sources of protein or fat. They are much more attractive to the palate than are most of the vegetables. They enjoy the popular reputation of possessing mild laxative properties, and tend to increase elimination by virtue of their mild diuretic qualities, part of which are due to the extra water consumption, and part to the action of certain salts of organic acids they contain.

Fruit juices or the edible parts of fruits differ from the cereal grains, and resemble in a very important respect the vegetables, which are morphologically tubers or roots. There is an excess of basic radicles which renders their ash alkaline, whereas most seeds give an acid ash. Meats are also of acid character. The meat and bread portion of our diet, when oxidized in metabolism leads to the formation of an excess of acid over base-forming substances. It is now a well established fact that a certain alkali reserve in the blood is essential to maintain its capacity to carry carbon dioxid to the lungs for elimination, and that a common pathological condition, acidosis, exists in which this reserve falls below normal. This forms sound reason why the addition of fruits and vegetables to the diet tends to the establishment of a proper acid-base equilibrium in the various fluids of the body.

The fruits differ from the leafy vegetables in containing little calcium. They resemble the tubers and roots insofar as they do not tend to supplement the deficiencies of seed or meat products in this respect.