One other new aspect recently dear to my heart is the source of fuel for the brain. While conventional medical wisdom has stated that the brain, the most highly metabolically demanding organ of the body, is totally dependant on carbohydrate (glycogen breaking down to glucose) for oxidative fuel, this is not totally true. While most adults on the standard modern world high carbohydrate diet will indeed suffer hypoglycemic discomfort, i.e. dizziness, irritability, poor concentration, intense hunger, etc., when blood sugar (glucose) levels drop as a result of prolonged lack of carbohydrate intake i.e several hours, aggravated by muscular exertion, the human body can adapt to a low carbohydrate diet if approached systematically and consistently. Indeed, there is very good evidence on which to argue that the human physiology we inherited was adapted through our evolution out of the trees to the savannah to tolerate long periods of no carbohydrate, depending only on our fat stores to keep us functioning until our next hunting kill and fat replenishment. The excess carbohydrate that the latest incarnation of Homo sapiens has in such abundance is merely a recent accidental development that our biochemistry and genetics has not yet successfully adapted to, and it is killing us.

Sorry, I got off track there; the short story is that when adapted to a consistently low carbohydrate diet, the human organism is much less dependant on glucose either for muscular activity or fro brain function, due to activation and augmentation of the metabolic pathways for oxidizing fat for fuel, instead of the now unavailable carbohydrate. The switchover to fat use in the brain is not absolute — the brain still needs about 40% of its requirement from glucose oxidation. However, since the muscles are not draining down the glycogen stores, there is plenty of glucose left over for the brain to be happy with. I have been fuelled exclusively on a low carbohydrate diet for the past 22 months with minimal violations of my self imposed protocol, and I have been very satisfied with the results. My exertional endurance in long running and triathlon events has been much enhanced, without the critical need to refuel with very high carbohydrate replacement on the fly. I don’t get desperately hungry on a daily basis if it gets too late after the last meal like I used to, and I don’t get irritable, shaky or poorly focused (i.e. symptoms of hypoglycemia) when I must eat. This experience is totally outside what I was taught in Medical School, and what I had been preaching throughout my medical career, much to my shame. This capability of humans to successfully switch to a fat fuelled system is still totally denied by the medical establishment. Indeed, what I have done to myself is stated to be foolhardy and dangerous by the conventional medical wisdom of today. The evidence supporting low carbohydrate living from controlled trials is slowly mounting, but the inertia of the past 40 years probably means it will take years before the truth will out and modern researchers can and will look at all the available evidence.

Oh, well, not my problem. My problem is to be sufficiently inspired by your teaching so as to continue to improve my swimming and get faster and more efficient in the water!