A small section of a much larger article entitled "the reality of food in the Bush" (published in the BushcraftUK magazine 'Bushcraft' in two parts, issues 1 and 2) which covers all aspects nutrition in the bush including rabbit starvation aka rabbit posioning:
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Many wild animals, especially small mammals have so little body fat that reliance solely on their meat for sustenance results in 'Rabbit starvation', a potentially fatal condition brought about by consuming a diet consisting almost entirely of protein. The most common historical example has been those attempting to rely entirely on rabbit meat.
Rabbits are one of the easiest animals to trap and it is easy for someone who is catching large numbers of rabbits to assume that they are providing themselves with all the calories their body requires; but this is not the case. A person who eats nothing but rabbit meat will begin to experience headaches, fatigue, and discomfort. If they continue to consume nothing but rabbit their stomachs become distended and after a week they develop diarrhea, but no matter how much they eat they will be unable to satisfy their hunger, eventually they appear to starve to death even whilst continuing to consume large quantities of rabbit meat.
This happens because rabbits have very little body fat, so the calories provided by their meat are almost entirely in the form of protein. For protein amino acids to be used as fuel they have to be converted into glucose by the liver in a process called gluconeogenesis, this metabolic process requires a large amount of energy in the form of adenosinetriphosphate (ATP). Six ATP molecules are used to convert the amino acids to glucose and a further four are required to convert the harmful Ammonia which is produced as a by product, into urea. The liver relies solely on aerobic metabolism to replace the ATP molecules that have been consumed.
The liver obtains around 80% of its oxygen from the portal vein which because of its venous nature has a low oxygen partial pressure; this scarcity of oxygen limits production of ATP, thus limiting the production of glucose from amino acids. By determining the maximal rate of urea synthesis and therefore the point at which glucose production ceases, it has been calculated that the maximum capacity of the liver to produce glucose from amino acids in an 80kg individual is restricted to approximately 250 grams a day (1000cal), not nearly enough to support an active person.
However this limitation of available calories is not sole cause of the symptoms described in those who have suffered and ultimately died from a protein exclusive diet, the true cause of the deaths resulting from this condition is far more insidious!
The liver begins the process of turning protein amino acids into glucose by removing the A-amino group made up of nitrogen molecules (ammonia) from the amino acids so that the remaining carbon skeleton can be utilized, this ammonia is highly toxic so under normal circumstances the ammonia is immediately converted into urea which can be safely removed by the kidneys. however if the livers ATP supply is exhausted due to a lack of available oxygen it cannot convert the toxic ammonia into urea and is forced instead to release the ammonia into the bloodstream.
The phenomenon of rabbit poisoning can now be explained as follows, an 80 kg person subsisting exclusively on protein can only provide their body with a maximum of 1,000 calories a day, because their liver is only capable of producing 250 grams of glucose from protein via gluconeogenesis regardless of how much protein they consume. Because of this lack of calories the individual is unable to satisfy their hunger through protein alone, but in a desperate attempt to ease their hunger with the only food source available to them they continue to consume protein unaware that the liver, unable to complete its breakdown of the amino acids into glucose due to a lack of oxygen is releasing highly toxic ammonia into the blood and the more protein they consume beyond the initial 250grams per day the more ammonia is building up in their blood where it damages the central nervous system.
This damage manifests itself progressively as irritability, headaches, vomiting, somnolence, coma, and finally death as a result of cerebral edema.
In summary, no matter how much protein you consume if you only eat protein you can only provide yourself with a maximum of 1,000 calories a day, the remaining calories must be provided in the form of fats and/or carbohydrates. If you attempt to consume more than 250 grams of protein a day in a diet consisting exclusively of protein you are simply poisoning yourself with ammonia and hastening your demise. - copyright 2006 Stuart P. Goring
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This explanation is based on my own research and is as far as I am aware is the first complete and feasible explanation for death via the exclusive consummation of protein.
