Francis M. Pottinger, M.D. Publishes ‘Pottenger’s Cat’s: A Study in Nutrition’

Between the years of 1932 and 1942, Dr. Francis Marion Pottenger, Jr. conducted a feeding experiment to determine the effects of heat-processed food on cats. His ten-year cat study was prompted by the high rate of mortality he was experiencing among his laboratory cats undergoing adrenalectomies for use in standardizing the hormone content of the adrenal extract he was making. Because there were no existent chemical procedures for standardizing biological extracts, manufacturers of such extracts necessarily had to use animals to determine their potency. As cats die without their adrenal glands, the dose of extract required to support their lives calibrated the level of the extract’s potency.

In his effort to maximize the preoperative health of his laboratory animals, Francis fed them a diet of market grade raw milk, cod liver oil and cooked meat scraps from the sanitarium. These scraps included the liver, tripe, sweetbreads, brains, heart and muscle. This diet was considered to be rich in all the important nutritive substances by the experts of the day, and the surgical technique used for the adrenalectomies was the most exacting known. Therefore, Francis was perplexed as to why his cats were poor operative risks. In seeking an explanation, he began noticing that the cats showed signs of deficiency. All showed a decrease in their reproductive capacity and many of the kittens born in the laboratory had skeletal deformities and organ malfunctions.

As his neighbors in Monrovia kept donating an increasing number of cats to his laboratory, the demand for cooked meat scraps exceeded supply and he placed an order at the local meat packing plant for raw meat scraps, again including the viscera, muscle and bone. These raw meat scraps were fed to a segregated group of cats each day and within a few months this group appeared in better health than the animals being fed cooked meat scraps. Their kittens appeared more vigorous, and most interestingly, their operative mortality decreased markedly.

The contrast in the apparent health of the cats fed raw meat and those fed cooked meat was so startling, it prompted Francis to undertake a controlled experiment. What he had observed by chance, he wanted to repeat by design. He wanted to find answers to such questions as: Why did the cats eating raw meat survive their operations more readily than those eating cooked meat? Why did the kittens of the raw meat fed cats appear more vigorous? Why did a diet based on cooked meat scraps apparently fail to provide the necessary nutritional elements for good health? He felt the findings of a controlled feeding experiment might illumine new facts about optimal human nutrition.

The Cat Study of Francis M. Pottenger, Jr., MD is unique. There is no similar experiment in the medical literature. The pathological and chemical findings were supervised by Francis in consultation with Alvin G. Foord, M.D., professor of pathology at the University of Southern California and pathologist at the Huntington Memorial Hospital in Pasadena. Accordingly, the studies met the most rigorous scientific standards of the day and their protocol was observed consistently.

Since The Cat Study is unique, its findings are frequently quoted and misquoted in order to justify the ideas of others. For example, one author of a popular selling book states that 200 cats died of arthritis; this indeed did not happen. Another author states that the cats were fed sprouts and survived in full health for four continuous generations. Again, no such experiment took place, and yet this misinformation has been traced over a dozen or more different articles and books.

A frequent criticism of The Pottenger Cat Study is that it was not properly controlled. Here it is necessary to ask, “By what standards?” Every one of the studies followed strictly defined protocol. All variables in the stock of the animals were reported and explained. Because some of the test procedures may seem crude forty years later, this in no way invalidates the facts that the procedures were meticulously controlled and that the results of the experiments were reported as observed.

Another criticism is that the cats were kept in an artificial environment unrelated to real living conditions. Such a criticism overlooks the experimental necessity of maintaining a controlled environment to provide valid findings. It also overlooks the evidence that given specific living conditions, specific changes repeatedly occurred in the health of the cats under observation.

Another frequent criticism is that the experimental work done on cat nutrition has no appropriate application to human nutrition. Francis M. Pottenger, Jr., MD never stated that a one-to-one comparison could be made between his findings in cat nutrition and his findings in human nutrition. He did say: “While no attempt will be made to correlate the changes in the animals studied with malformations found in humans, the similarity is so obvious that parallel pictures will suggest themselves.”

All too often, self-appointed authorities will state categorically that they do not believe other’s observations and so seek to close the door on any further inquiry into these observations. They declare, “Because I do not believe the facts as presented, they are not so.” Far better for science if responsible individuals maintain an attitude of open inquiry and test the observations of others before forming rigid opinions. In the case of The Cat Study, human welfare might well be served of concerned researchers made every effort to discover if valid correlation’s can be made between cat nutrition and human nutrition. It must be remembered that cats and humans both are mammalian biological systems.

It would be of great value to the field of nutrition to repeat The Cat Study within the parameters of present day technology and with the use of present day antibiotics. Most of the cats on deficient diets died from infections of the kidneys, lungs and bones. If these infections were eliminated as a cause of death by antibiotics, it would allow the cats to reveal their ultimate degenerative fates. As an extension to this experiment, it would be of interest to study the effects of vitamin and mineral supplementation in the diet of cooked food fed animals.

It is our effort in this monograph to present the observations made by Francis M. Pottenger, Jr., MD on the effects of deficient and optimum nutrition in cats and human beings as recorded in his articles and clinical records written between the years of 1932 and 1956. Nothing has been added or subtracted from his findings, and for the most part, the words describing his work are his own. Though some of the scientific interpretations have not withstood the test of time, the observations are valid. A careful and selective interpretation by an inquiring mind will readily differentiate the two.

By Ron Schmid, ND

The impact of quoted work is often influenced by the reputation of the person quoted. But what makes a reputation, in particular that of a person who died many years ago? Certainly in part the accuracy and importance of the written work left behind. But when a person’s life and work are ignored by most of society, much less maligned by prestigious segments, reputation suffers. What yardstick may we use then to evaluate the import of the life? We may be left with only our judgement of the work itself. If the work is complex and perhaps not readily available, as is Dr. Pottenger’s, making that judgement may be difficult.

Thomas Hotchkiss knew Francis M. Pottenger from the time Thomas was eleven years old in 1912. His “Personal Memoir” of Francis, written after his death in 1967, provided me with the following details about Francis’s life.1


Two years before his death, Pottenger received the Distinguished Alumnus Award at Otterbein College in Ohio. In presenting the citation, the Chairman of the Board of Trustees praised Pottenger’s distinguished career in medicine and public service.

Service indeed. By the time he received that award, Francis M. Pottenger, MD, had published over fifty peer-reviewed articles in the scientific literature, mainly in the fields of medicine, chronic disease and nutrition. He had served as president of the Los Angeles County Medical Association, the American Therapeutic Society and the American Academy of Applied Nutrition. “Francis was among the first in his profession to recognize the hazard to health caused by air pollution in Los Angeles County. He worked indefatigably over a period of many years to mitigate its deleterious effects upon human health. His efforts were widely recognized and as a result he became a member of the Los Angeles County Air Pollution Control District’s Scientific Committee on Air Pollution.”

Pottenger received a rather unusual accolade for a medical doctor. In 1951, the Texas State Dental Association honored him with an award for the Advancement of the Science of Dentistry in Texas. He had written a number of brilliant articles on the effect of raw versus cooked foods, including pasteurized milk, on the dental and facial structures of animals and human beings. The articles had a powerful and lasting impact on the many American physicians and dentists who were actively interested in the effect of nutrition on human health and disease.

In 1940, Francis founded the Francis M. Pottenger, Jr., Hospital at Monrovia, California, for the treatment of asthma and other nontubercular diseases of the respiratory system. And beginning in 1945, he was Assistant Clinical Professor of Experimental Medicine at the University of Southern California.

Dr. Pottenger also served as Medical Service Chief for the Civil Defense Area surrounding his home during World War II. Japanese invasion of the West Coast of America was considered a real threat in the dark days just after the 1941 attack on Pearl Harbor. The project to set up the first portable hospital in Los Angeles County under simulated disaster conditions was directed by Pottenger.

The Pottenger Cat Study is the work that brought him fame. There’s no money these days in making famous a man who proves the value of raw foods; in the last forty years or so, Pottenger’s fame in the conventional medical and nutritional establishment has faded as surely as the stocks of processed food companies have risen. Yet he remains an icon to those who understand his work and its importance, particularly in relationship to the work of Weston Price. Let’s look now at what Francis had to say in one of his many professional papers, and an example of how his work has not only been misunderstood and ignored, but indeed sometimes deliberately misrepresented.


A fetish is defined as 1) a thing abnormally stimulating or attracting sexual desire and 2) an inanimate object worshiped by primitive peoples for its supposed inherent magical powers or as being inhabited by a spirit. b. a thing evoking irrational devotion or respect.2

For many years, advocates for raw milk have pointed to Pottenger’s work as perhaps the most important research that proves raw milk’s benefits. Those who would outlaw the sale of all raw milk have meanwhile disparaged and distorted his work. An example of the latter is found in an article titled “Unpasteurized Milk-The Hazards of a Health Fetish” that appeared in the Journal of the American Medical Association on October 19, 1984.3 The authors refer to a 1946 Pottenger article from the American Journal of Orthodontics and Oral Surgery, “The Effect of Heat-Processed and Metabolized Vitamin D Milk on the Dentofacial Structures of Experimental Animals.”4

The authors of the “Health Fetish” article state: “Numerous studies of the relative nutritional merits of raw and pasteurized milk have been conducted in animals and humans, and no differences were detectable. One animal study deserves particular attention because a misrepresentation of the results has become prominent in the raw milk folklore. In 1946, Pottenger published a report about his observations on cats fed varying combinations of raw and heat-treated milk and raw and cooked meat. In his first and largest series of experiments, Pottenger observed many diseases in cats fed raw milk and cooked meat. Raw milk advocates have erroneously cited this article as having reported that disease occurred in cats fed pasteurized milk. Smaller experiments in the same article showed that a diet of one-third raw meat and two-thirds milk (pasteurized or not) did not provide adequate nutrition for the cats.”

Based on this quote, one might reasonably think that perhaps the diseases Pottenger observed in the first series of experiments were caused by raw milk, and that the smaller experiments showed that raw milk was not superior nutritionally to pasteurized milk. Publication in so prestigious a journal by two medical doctors and two veterinarians lends further weight to the pronouncements.


Dr. Pottenger originally had the cats because he used them in his studies to help human patients. The cats had their adrenal glands removed as part of his research. Otherwise, they were healthy and well cared for. They were fed cooked meat scraps which included internal organ meats and bones along with some additional raw milk and cod liver oil. This diet provided what at the time was considered an optimal amount of nutrients and the cats seemed healthy. Nevertheless, the cats had an unexplainably high mortality rate. Then, due to a change in the number of cats in the study, raw meat scraps replaced the cooked meat in the diet of certain cats. Within a very short period of time the mortality rate dropped significantly. The raw meat fed animals began to have much better survival rates and they continued on a superior quality of health. Pottenger then began ordering raw meat scraps from a local meat packing plant – including organs, meat, and bones – and fed a separate group of cats from this supply. Within months this separate group appeared in better shape than the cooked meat group and their offspring were healthier. Pottenger was intrigued by what he termed “heat label factors” and he asked himself if the cooking process somehow rendered food nutritionally deficient, causing eventual physiological degeneration.

He decided then to begin a controlled scientific study which can be divided into two parts: the meat study and the milk study. For the purpose of the study the animals were divided into different groups where they were fed either cooked or raw animal-based foods. This consisted of cooked meat versus raw meat, and pasteurized dairy versus raw dairy. The cats chosen for the study were kept in open air pens with a yard four feet wide, seven feet high and twelve feet long.

Meat Study

Pottenger divided this study into two groups. In Group A, the cats were fed a diet of 2/3 raw meat, 1/3 raw milk, and cod-liver oil. In Group B, they were fed a diet of 2/3 cooked meat, 1/3 raw milk, and cod-liver oil.

The cats fed the all-raw diet were healthy while the cats fed the cooked-meat diet developed various health problems. By the end of the first generation the cooked-meat cats started to develop degenerative diseases and became quite sedentary. By the end of the second generation, the cats had developed degenerative diseases, changes in their skeletal structure were evident and the calcium content of their bones had fallen to ten percent. At sixteen weeks of age the second generation raw-meat kittens weighed 2000 gram average while the second generation cooked-meat animals only weighed about 1600 grams.

By the end of the third generation the cooked-meat cats had developed degenerative diseases very early in life and some were born blind and weak and had a much shorter life span. Many of the third generation cats couldn’t even reproduce. Most of these adult cats were void of interest in sex and those that attempted to mate could only produce stillborn litters. Kittens of the third generation did not survive six months. The cats died out totally by the fourth generation. Skin diseases and allergies increased from an incidence of five percent in normal cats to over 90 percent in the third generation of deficient cats. The fur of the deficient cats lost its sheen and shedding was noticeable. Males became docile while females became more aggressive. The skull was considerably smaller, flat with pointed features and the bones were paper thin and soft like sponge rubber. The calcium content of the bone had fallen to a low three percent by weight. On the other hand, the raw meat animals continued to reproduce healthy offspring generation after generation.

Milk Study

In this study, the cats were fed 2/3 milk and 1/3 meat. All groups were fed raw meat with different groups getting raw, pasteurized, evaporated or sweetened condensed milk.

The raw milk fed cats were the healthiest; they moved about the pen with a great agility and coordination. Their fur was shiny and soft and they presented normal sexual interest. They would land on their feet when thrown in the air.

The cats not being fed raw milk exhibited varying degrees of health problems similar to the previous cooked meat study.

The pasteurized milk fed cats moved about the pen in a manner quite different from the raw milk fed cats and some developed arthritis, skeletal changes and lessened reproductive efficiency. Lethargy was present in all of these cats, with apparently no energy at all. Their offspring presented progressive constitutional and respiratory problems. These animals exhibited an impaired sense of coordination when thrown a short distance. Dental deterioration, abscesses and gingiva inflammation were a frequent finding. All of these changes were similar to the cats of the first, second and third generations eating cooked meat.

The evaporated milk fed cats showed even greater deterioration than their pasteurized milk fed counterparts with the most marked deficiencies occurring amongst those fed sweetened condensed milk.

The sweetened condensed milk fed cats not only had their milk heat-processed, but there was the addition of sugar. There was marked deterioration in coordination and dental abnormalities in this group. These cats developed much heavier fat deposits and exhibited severe skeletal deformities and were prone to bone fractures. They were very nervous animals showing extreme irritability and often paced back and forth in their pens.

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