The body is so constructed that every organ has a factor of safety. A very large amount of the liver, for instance, can be diseased before any failure in its function is detectable. The same is true of the kidneys and of the heart, and the factor of safety in the case of the pancreas explains why we do not all have diabetes. Very few people have a normal pancreas, because inflammations in organs near the pancreas are fairly common; for instance, inflammation of the gallbladder, and very frequently the pancreas is involved in such inflammation. However, the number of persons with known gallbladder disease who develop diabetes, is not appreciably greater than that of persons without any evidence of such inflammations.
Hardening of arteries a cause of diabetes.—The pancreas may be injured, as is true of all of the organs of the body, by disturbance of its blood supply, especially through hardening of the walls of the arterial tubes which bring it its blood, and narrowing of their lumens or passageways. Older persons with hardened arteries may develop diabetes in this manner. On the other hand, many persons have extreme arterial disease and consequent destruction of pancreatic islands without diabetes.
Infections a cause of diabetes.—The delicate tissues of the pancreas, just as in the case of other organs, may be poisoned in the course of a general disease, such as scarlet fever, mumps, or influenza and, in consequence, diabetes may result from such diseases. There is, however, nothing specific in this. A certain number of cases of diabetes can be traced to a preceding acute intoxication of this character, but it is by no means true that any one of the known infections is always followed by diabetes.
Functional overstrain the chief cause of diabetes.—Functional overstrain is a recognized cause of disease, especially of the heart, but also of other organs. The heart may be irreparably injured by excessive exertion. Functional overstrain of the pancreatic islands resulting from long continued overeating is a cause of much diabetes. Persons who persistently overeat are usually markedly overweight. Some thin people are also equally prone to overeat, and yet, for some thus far unknown reason, remain thin.
Obesity a mark of overeating and functional overstrain of the pancreas.—The rule, however, is that overeating leads to obesity, and it is a well known fact that many diabetic patients are, or have been, overweight. Dr. Joslin, for instance, found among 1,000 diabetic patients, 75 per cent who either were, or had been, over normal weight. Dr. Joslin says that it takes ten diabetic patients to make a ton of diabetes. Overeating with attendant long continued functional overstrain of Langerhans islands is probably the most common of all causes of diabetes.
Sugar eating.—It is of considerable significance that the increasing incidence of diabetes in America is coincident with the enormous increase in the sugar consumption. In the decade 1880 to 1890, the annual sugar consumption was 44 pounds per capita. In 1921, it had risen to 84 pounds, and in 1922 to 103 pounds. The death rate for diabetes in 1890 was 5.5 for each 100,000; in 1921, it was 16.8 for each 100,000. It is easier to overeat of sugar than of almost any other food known, and it is probable that sugar imposes a greater functional strain on the pancreas than do the starches or fats. Starches swell up and fill the stomach readily, thus checking the appetite; furthermore they are slowly absorbed into the blood. Sugar goes into solution, passes the stomach quickly, is absorbed almost instantly and at once demands attention from the pancreas. The common desserts are sweets. When we are glutted with meat and potatoes, we still have room for sweets and we can always find room for candies. The rage for soft drinks since the abolition of alcoholic beverages is certain to increase the crop of new cases of diabetes. I have seen several patients who have been suddenly precipitated into an extreme stage of diabetes and coma by a soft drink spree.
Diabetes may occur without provocation.—Not infrequently, among younger persons and children, diabetes appears out of a clear sky with apparently no provoking cause. No inflammation has occurred in the pancreas of these patients, so far as any good evidence shows; they are young and therefore not afflicted with arterial disease, and they have never been overweight and have not overeaten. How can we explain the diabetes of these children and young persons, and how can we explain why some fat persons and not all escape diabetes, and why some patients with very little disease of their pancreas have diabetes and others with very extensive destruction of the pancreas do not have it?
Heredity of the tendency to diabetes.—The answer, probably, lies in the more or less shadowy realm of heredity. Some of us are born with weak eyes and others with weak islands, and the degree of original island weakness determines the susceptibility of the islands both to functional overstrain from overeating and to injury from infectious diseases or from poor circulation of the blood. If the diabetic tendency of an individual is marked, diabetes may develop, in very early life. The pancreas here is too weak to withstand the normal functional strain of growth. When this is the case, the disease is of extreme severity. If the diabetic tendency is slight, it may not show itself except as the result of long continued overeating. If the pancreatic islands are functionally strong, they withstand infections and injury from disease or poor blood supply; if weak, they fail and diabetes results. Diabetes rather infrequently occurs in several members of the same family, but the fact that this happens rather infrequently does not mean that the tendency fails to pass by heredity. Many persons who are considered normal may have this tendency without showing any evidence of it throughout life.
THE TREATMENT OF DIABETES
Prevention.—A stitch in time will save nine diabetic patients. Typhoid, small-pox, diphtheria, yellow fever and a number of other diseases have been practically eliminated. Tuberculosis, otherwise known as the white plague, is rapidly being chained. Why not do the same with diabetes? We have seen that overeating is the common cause. Let us, therefore, teach the virtues of keeping lean and fit. Incidentally, such teaching may help to control other chronic diseases. There is reason to believe that heart trouble, high blood pressure, gallstone and cancer, occur in the obese with greater frequency than in the lean. Obesity is a mark of long continued functional overstrain of all the organs of the body. Overeating of carbohydrates and proteins is especially injurious to the pancreas. In Berlin, during the war when the food supplies of the populace were greatly reduced and sugar and meat in particular were scarce, the number of new patients with diabetes decreased immensely. In America, with growing luxury and rising sugar consumption, diabetes is increasing by leaps and bounds. The Jews, as a race, have much diabetes, not because they are Jews, but because so many of them are luxury lovers, overeaters, and fat Jews. Diabetes cannot be entirely eliminated by preventing overeating. As we have seen, thin people are not immune if the heredity tendency in them is strong; and they develop the severest form of diabetes at a relatively tender age, and yet it is possible that even the number of these may be reduced in time. A leading authority once published the family trees of a number of diabetic families and these family trees suggest that the tendency to diabetes becomes stronger with each succeeding generation. In the grandparents the disease was mild and came on late in life—not until they had overeaten, presumably, for many years and were fat. In the parents the disease was more severe and appeared earlier in life, the result, presumably, of less overeating. In the third generation, the disease occurred in the children with still less provocation from overeating. Perhaps we can save our grandchildren, therefore, by keeping ourselves fit, and thus stamp out the diabetes of childhood which is always severe and, therefore, the most dreaded. It is worth a trial.