diabetes diet

The last topic will serve as an introduction to Part II. Here, Medbio presents a repeatable experiment conducted on rats used to determine the ability to replace glycogen. There are many articles detailing the differences between rats and humans[1], ultimately, though, rats and mice are the most commonly used vertebrate species because of their size, low cost, ease of handling, and fast reproduction rate.[2]

“The question addressed in the following experiment is "does the choice of diet after a fast alter the liver's ability to replace glycogen used to replace blood glucose?" All of the rats used in this experiment were fasted overnight. Three of these were then offered either bread (a carbohydrate-rich diet), dried fish (a high-protein diet) or butter (a fat-rich diet) and allowed to eat for one day. Their livers were then removed and glycogen was extracted. This stored carbohydrate represented the glucose these animals obtained from the diets that was in excess of their immediate energy needs.

Analyzing the glycogen content of the liver extracts usually obtain the following results:

Diet	Liver Glycogen in mg / gram of liver
24 hour fast	7.8
Fast + 24 hours of eating bread	66.8
Fast + 24 hours of eating dry fish	21.3
Fast + 24 hours of eating butter	7.1

As shown in the figure above, ingested carbohydrates are rapidly used in rats (and humans). Liver glycogen becomes the major source of circulating glucose within 2-4 hours after a meal; the so-called postpranial period. The very low levels of liver glycogen seen after a day's fast follow the extensive use of this material to stabilize blood glucose. Since the fasting period was so long (a day is a long time for a rat), the animal had to produce blood sugar from amino acids taken from its own proteins.

Bread is an excellent source of starch and is a carbohydrate supply limited only by appetite. This rat ate extremely well, literally making a cave in the bread and living in this delicious tunnel of food. Starch is absorbed as glucose and is rapidly stored as glycogen in both muscles and the liver. It is interesting to note that the level reached following refeeding after a fast exceeds that normally seen. It would seem that the body learns of experience, guarding itself against another fast. This effect lasts for two days or more in humans and is seen in both liver and muscle. The "overshoot phenomena" of glycogen levels is well-known in athletic circles and is used by many to build up an energy reserve before sports competitions.

The fish product used in this experiment was prepared from cod, a lean fish. This animal received almost only protein as an energy source in its diet. Nevertheless, we see that this animal managed to increase its liver glycogen level markedly, indicating that it was able to produce glucose from the fish protein. Furthermore, there was a good bit in excess of that was used as an energy source and this was saved as glycogen. That works in rats, but not for you and me. Rats have a proportionally larger liver than humans. This allows a much higher rate of gluconeogenesis and ureogenesis than that seen in humans. People who try to survive on high-protein low-fat diets experience weakness, fatigue, intestinal distress and weight loss. This has been called "rabbit starvation".

Rabbit Starvation

Another myth about primitive diets, and one that is harder to dispel, is that they were low in fat, particularly saturated animal fat. Loren Cordain, PhD, probably the most well known proponent of a return to Paleolithic food habits, recommends a diet consisting of "lean meat, occasional organ meats and wild fruits and vegetables." While this prescription may be politically correct, it does not jibe with descriptions of Paleolithic eating habits, either in cold or hot climates. Vilhjalmur Stefansson, who spent many years living with the Eskimos and Indians of Northern Canada, reports that wild male ruminants like elk and caribou carry a large slab of back fat, weighing as much as 40 to 50 pounds.

The Indians and Eskimo hunted older male animals preferentially because they wanted this back slab fat, as well as the highly saturated fat found around the kidneys. Other groups used blubber from sea mammals like seal and walrus. The groups that depend on the blubber animals are the most fortunate in the hunting way of life," wrote Stefansson, "for they never suffer from fat-hunger. This trouble is worst, so far as North America is concerned, among those forest Indians who depend at times on rabbits, the leanest animal in the North, and who develop the extreme fat-hunger known as rabbit-starvation.

Rabbit eaters, if they have no fat from another source-beaver, moose, fish-will develop diarrhea in about a week, with headache, lassitude, a vague discomfort. If there are enough rabbits, the people eat till their stomachs are distended; but no matter how much they eat they feel unsatisfied. Some think a man will die sooner if he eats continually of fat-free meat than if he eats nothing, but this is a belief on which sufficient evidence for a decision has not been gathered in the north.

Deaths from rabbit-starvation, or from the eating of other skinny meat, are rare; for everyone understands the principle, and any possible preventive steps are naturally taken. Normally, according to Stefansson, the diet consisted of dried or cured meat "eaten with fat," namely the highly saturated cavity and back slab fat that could be easily separated from the animal.

Another Arctic explorer, Hugh Brody, reports that Eskimos ate raw liver mixed with small pieces of fat and that strips of dried or smoked meat were "spread with fat or lard. Pemmican, a highly concentrated travel food, was a mixture of lean dried buffalo meat and highly saturated buffalo fat (Buffalo fat, by the way, is more saturated than beef fat.). Less than two pounds of pemmican per day could sustain a man doing hard physical labor. The ratio of fat to protein in pemmican was 80%-20%. As lean meat from game animals was often given to the dogs, there is no reason to suppose that everyday fare did not have the same proportions: 80% fat (mostly highly saturated fat) to 20% protein-in a population in which heart disease and cancer were nonexistent.

See “Traditional Diets,” at the Weston Price website online at http://westonaprice.org/traditional_diets/nasty_brutish_short.html. Retrieved on 3/1/08. Op cit. http://www.medbio.info/. Retrieved on 3/2/08.

Butter is essentially a pure fat product, consisting almost entirely of triglycerides. The rat fed butter had a very low liver glycogen level. It essentially experienced a two-day carbohydrate fast. Glucose cannot be synthesized from the fatty acids resulting from the breakdown of triglycerides. This results from the fact that fatty acid oxidation produces solely 2-carbon fragments. These are further metabolized in the citric acid cycle. Here, two molecules of CO₂ are lost from the cycle for each 2-carbon fragment that enters. Therefore, no net synthesis of the precursors of glucose can take place. The fat-fed rat could not obtain glucose from the diet and, presumably, had to use its endogenous proteins to support the level of blood glucose.

We have not experimented with this kind of diet here but a few comments are required. Diets comprised of 20-30% protein and with little or no carbohydrate have been known for hundreds of years. Such a diet can function well as a source of energy for humans. We do not need to eat carbohydrates at all; we can produce all the glucose we need from dietary proteins. The catch is that we can only get something like 1000-1500 kilocalories daily from glucose made from amino acids. We must cover at least half of our caloric requirements from fat in addition to proteins. This is the makeup of pemmican, the meat and fat mixture used by Indians, Eskimos and Lapps for thousands of years.”[3]

Of course, rats and humans do differ, but this experiment can be repeated with consistent results. The conclusions for humans based upon this experiment, although not exactly the same, are most likely to be similar; that is, eating only fat after fasting will not add to liver glycogen stores, but eating both carbohydrate and protein, will. Eating enough carbohydrates will fill liver glycogen stores to capacity; eating protein after fasting will add to liver glycogen stores, but not fill it. Finding the exact differences between rats and humans regarding liver glycogen stores isn’t necessary; besides, most rational people would probably prefer to continue using their livers once the experiment ends.[4]

[1] See for example http://www.pcrm.org/resch/anexp/rats.html. Retrieved on 3/8/08. See also http://www.curedisease.com/Perspectives/vol_1_1989/Rats%20to%20Animal%20Models.html. Retrieved on 3/8/08. For online information on animal testing in general, see http://en.wikipedia.org/wiki/Animal_testing. Retrieved on 3/08/08.

[2] See Rosenthal N, Brown S. "The mouse ascending: perspectives for human-disease models," Nat. Cell Biol, Volume 9, issue 9, pp. 993-9, 2007. PMID 17762889. Available online at http://www.ncbi.nlm.nih.gov/pubmed/17762889. Retrieved on 3/08/08.

[3] See the section “Diet and liver glycogen levels” at http://www.medbio.info. Retrieved on 3/2/08.

[4] Protections for human subjects of research are required under Department of Health and Human Services (HHS) regulations at 45 CFR 46. Subpart A of the HHS regulations constitutes the Federal Policy (Common Rule) for the Protection of Human Subjects, which has been adopted by an additional 16 Executive Branch Departments and Agencies. Each institution engaged in (non-exempt) HHS-supported human subjects research must provide a written Assurance of Compliance, satisfactory to the Office for Protection from Research Risks (OPRR), that it will comply with the HHS human subjects regulations. - 45 CFR 46.103(a)

Institutions conducting (non-exempt) HHS-supported human subjects research must provide Certification to the supporting agency that the research has been reviewed and approved by an Institutional Review Board (IRB) designated under an OPRR-approved Assurance. Under no circumstances may (non-exempt) human subjects research be supported prior to Certification. - 45 CFR 46.103(f). Except where the IRB specifically approves a waiver in accordance with HHS regulations, no investigator may involve a human being as a subject in (non-exempt) research unless the investigator has obtained the legally effective informed consent of the subject, or the subject's legally authorized representative. The meaning of "legally effective" and "legally authorized" is determined in part by applicable State law. See “Summary of Basic Protections for Human Subjects,” December 23, 1997, Office for Protection from Research Risks. Available online at http://www.hhs.gov/ohrp/humansubjects/guidance/basics.htm. Retrieved on 2/15/08.