Recent investigations have shown that food furnishing sufficient amounts of proteins, fats, carbohydrates, and inorganic foodstuffs may not always prove permanently adequate. Some at least of the food materials which go to make up a completely adequate diet must have properties beyond those which have been considered in the preceding chapters. For the present these additional properties are best expressed in terms of their physiological effects. The term "deficiency diseases" has been introduced as a designation for those disorders which are thought to be due to dietary deficiencies of this sort, and the nature of the disorder arising from the use of any given diet serves to designate the property which has to do with the cause or prevention of the disease. Scurvy and beriberi have in recent years been considered the typical deficiency diseases. In normal nutrition the occurrence of scurvy is prevented by the antiscorbutic properties of the food. Beriberi is primarily a disease of the nerves, a neuritis, and can be prevented by the use of food adequate in antineuritic substances or properties. Similarly some foods have growth-promoting properties beyond what can be accounted for by the proteins, fats, carbohydrates, and salts which they contain.

As our knowledge in this field is not yet sufficiently developed to permit a satisfactory chemical classification of the subject matter, the antiscorbutic and antineuritic properties of foods will be considered in this chapter, and the growth-promoting properties in the next. The reader should keep clearly in mind the fact that these are matters of active investigation at the present time so that even while this is being printed, new results tending to modify our views on these subjects may appear. The present text is written chiefly in the light of such investigations as were available in May, 1917.

Scurvy And The Antiscorbutic Property Of Food

For centuries scurvy was one of the most common diseases in Europe and at times among people of European races in North America. It was most frequent and most severe in the more northern regions, where the people were often confined to a limited and monotonous diet of bread or other grain products and meat or fish through a large part of the year. As a rule fruits and vegetables were eaten only during their short natural season.

On the long voyages which followed the discovery of America, sailors were often obliged to subsist for many months at a time on food even more restricted in variety than that of the winter diet of Europe because they were cut off not only from supplies of fresh fruits and vegetables but also from fresh meat. Their food supplies thus often consisted essentially of breadstuffs and salted meats. On such voyages there were many exceedingly severe outbreaks of scurvy and it gradually came to be recognized that scurvy might be expected when men were kept for a long time on diets which lack fresh food.

The European sailors whose experiences on their long voyages to America did so much to establish the relationship between diet and scurvy and the fact that fresh foods, particularly fresh fruits and vegetables, have antiscorbutic properties, were also instrumental in bringing about a great diminution of the disease. They introduced into Europe from America the cultivation of the potato and since that time, as potato culture and the use of potatoes as food throughout the year have become more common in Europe, scurvy has become less common.

For the past two or three generations serious epidemics of scurvy among adults have not often occurred except as the result of crop failure, imprisonment with inadequate food supply, or siege.

In all such cases of which we have accurate accounts the common feature appears to be the lack of potatoes or other fresh vegetable or fruit in the diet. Scurvy on shipboard is now avoided by carrying more liberal quantities of potatoes among the rations, and, in case of long voyages, the juice of lemons or limes is taken specifically for its antiscorbutic properties.

Garrod called attention to the fact that foods shown by experience to have good antiscorbutic properties (potatoes, lemon and lime juices, fruits and vegetables generally) are rich in potassium; and suggested that the cause of scurvy may be too small an intake of potassium - particularly of "acid vegetable potassium" convertible into potassium carbonate on oxidation.

However, the tendency of scurvy to occur epidemically (as well as some other pathological features) has also seemed suggestive of a bacterial origin and Litten after weighing the evidence available in the early years of this century wrote:* "However fascinating the potassium theory may be, it is by no means absolutely proven, and it does not contradict the view that scurvy may, in spite of this, be an infectious disease. Scurvy may perhaps be assumed to be an infectious disease of a non-contagious nature produced by a microorganism which finds in a body deficient in potassium a favorable culture medium for its development."

Wright, impressed with the fact that experience has shown scurvy to develop in cases in which the diet contains a preponderance of "acid forming" foods such as bread and meat, while foods of high antiscorbutic value, i.e. fruits and vegetables, are such as yield alkaline ash, was led to advocate the view (held also by Gautier) that the cause of scurvy is a sort of acidosis due to the constant production of a relative excess of acid in metabolism. An outbreak of the disease among the English soldiers besieged in Ladysmith during the Boer War gave Wright an opportunity to test his views and he found that in the scurvy patients the "titration alkalinity" ("alkali reserve") of the blood was considerably below normal and that by feeding sodium or potassium salts of organic acids such as acetate, citrate, or lactate he was able to effect a rapid improvement both in the scurvy symptoms and in the blood alkalinity.

* Cabot's Diseases of Metabolism (translation from Die Deutsche Klinik), p. 399.