To prevent these symptoms of undernourishment, KARL PETREN (1868-1927) advocated a veritable "fat diet" (WILDER), with, as its chief feature, a drastic reduction of proteins. The carbohydrates were restricted to leaf vegetables, and in spite of its lack of balance, the diet did enable diabetics to work and allowed diabetic children to grow more or less normally (NEWBURGH and MARSH).

Karl Petren. 

A Leader in Pre-Insulin Dietary Therapy of Diabetes by RUSSELL M. WILDER 

One of the most distinguished medical teachers and clinical investigators of his time was Karl Petrén. Some of his biographers have called him the most distinguished in Sweden. We know him in America principally because of his studies of diabetes and his advocacy in the very early nineteen twenties of a diet very high in fat. He was even more renowned, however, in neurology, and participated actively in Swedish public health affairs, notably in programs for the control of tuberculosis. 

Born in 1868 of a line of clergymen on his mother's side, one of five brothers all of whom became outstanding, his medical training in Lund was followed by a year of study under the guidance of Dejerine, in Charcot's former clinic, the Salpetriere, in Paris. An equally lengthy sojourn was with Naunyn in Strassburg, then in Germany. He was called in 1902 to the professorship of internal medicine at Upsala, and in 1910 to the chair of medicine in his alma mater, the University of Lund. It was not until he took the professorship at Lund that Petren's scientific interest was drawn to diabetes. Thereafter this became a major concern to him, largely because of dissatisfaction with the then current treatment by starvation. Extensive facilities and many patients with diabetes of severity, whom he could maintain for months and years under continuous supervision, enabled him to conduct extensive clinical and laboratory observations, employing various dietary procedures and ultimately arriving at conclusions of significance. 

It is true that others, before Petren, among them especially Weintraud, also a pupil of Naunyn, had found protein restriction to be beneficial in diabetes; but Petren's studies went much further in revealing, as they did, that an increase of the nitrogen exchange would aggravate pre-existing acidosis, and that, with a rigidly restricted protein intake, even in patients with diabetes of severity, fat possessed a nitrogen sparing effect not much inferior to that possessed by carbohydrates in the normal. Thus the Petren diet, as finally developed, became sufficiently high in fat to provide the calories required to maintain near normal body weight and this diet, to the surprise of everyone, could be tolerated without augmenting acidosis. Petren's diets also were restricted in their carbohydrate content to that contained in leafy vegetables, and almost always, by these means, blood sugar levels, in chronic cases of severity, could be held near normal. Because of the war (1914-1918) Petrem's early work on diabetes came to our attention late. The procedure, developed independently by Newburgh and Marsh [1], closely resembled that which he was recommending; also, without knowledge at the time of Petren's observations, I conducted a metabolic study with Boothby and Beeler [2], and our findings were in support of his conclusions. His high fat diets were opposed, nevertheless, in many quarters and controversy raged until the discovery of insulin, in 1922, which soon permitted liberal diabetic diets and put an end to further need for such procedure. However, certain facts, brought to light by Petren's studies and those of the others to whom I have referred, ought not to be forgotten: that fat like carbohydrate spares protein and that uncompensated acidosis, even when diabetes is severe, does not follow fat combustion if the nitrogen exchange is low and a minimal amount of carbohydrate is tolerated. Petren traveled widely and became an intimate of many of the foremost internists and neurologists in Germany, France, England and Scandinavia. He visited the United States and Canada before his death and left most pleasant memories of him here. Those who went to see him and his gracious wife, in their friendly home in Lund, found a generous and charming host. He was a gourmet nonpareil. He loved good food and vintage wines, which explains perhaps his indignation at the starvation of the diabetic patients of the period. 

Petren was said by those who studied under him to have been a forceful teacher. I can well believe it, recalling as I do an apt analogy he drew between the defenses of the body and those of a European state, in danger always of sudden invasion by a foreign power. The buffers of the blood, bicarbonates and phosphates, are like the standing army of the state, ready for battle at a moment's notice; the ammonia mechanism, whereby the fixed bases of the blood are preserved in long-standing ketogenic acidosis, like the army of reserves, takes time to mobilize. Also, just as the country's army of reserves, its national army when mobilized, takes over and permits the standing army to be brought back to former strength, so too the carbon dioxide combining power of the blood, though depleted in the early combat with accumulating keto-acids, again may be restored to normal levels when the rate of mobilization of ammonia has been sufficiently increased. 

Petren was a fervent advocate of international cooperation, especially in the world of science. Following World War I he labored mightily to bring together, as promptly as might be, the colleagues from the opposing sides in that dreadful conflict. He nevertheless was a nationalist at heart, the civilized type of nationalist. I well recall his enthusiastic pleasure at the rolling landscapes of southeastern Minnesota. "Just like Sweden," he would say. "I have seen nothing so lovely since I left my home." Petren's magnum opus, his "Diabetes-studier," a volume of 1000 pages, published in Copenhagen in 1923, with his assistants, Smith, Otterstrom, Odin and Malmros, with a foreword by B. Naunyn, stands as a landmark, as Naunyn expressed it there, between two eras of research on diabetes