from Dad

SOME CONTROVERSIAL MATERIAL BUT IN GENERAL CURRENT BEST THINKING -IMHO -
THERE SEEMS TO BE A VALID PLACE FOR OCCASIONAL FASTING IN HUMAN NUTRITION - WISH I KNEW THE OPTIMAL IMPLENTATION

Sunday, September 16, 2007
Mother Nature's Brain Fuel
9/16/2007 7:23 AM MST

( Brain Science )


The primary fuel sources the body uses to generate energy are fat and glucose. We are only able to store enough glucose to last for 24 hours. Well before that, we start breaking down protein and turning it into glucose. This is done to keep the brain humming along because it is not able to burn fat. If we don't eat for longer time intervals then what happens? We have an almost unlimited capacity for storing fat, so why not tap into that? That makes sense and is exactly what happens. The only problem, at least for the brain, is where does the glucose come from that it requires since fat can't be turned into glucose in any meaningful amount. Protein is the ultimate raw material used by the body to produce glucose for the brain. In essence, the body is cannibalizing muscle to turn it into glucose for brain food. Obviously, if this continues we would lose skeletal muscle, heart muscle and the protein in organs like liver and kidney. Several ingenious metabolic changes emerged during our evolutionary past to address this quandary.

As fat is utilized during a fast, it goes through a process in the liver where in the partially metabolized state it may be turned into ketone bodies which include acetoacetate and hydroxybutyrate. These are released into the circulation where many organs may use them as an alternative fuel source. The brain is one such organ. This change in fuel use by the brain may take place immediately, but to fully make the transition takes a week or two. When fully engaged, ketones may produce almost half of the energy the brain requires (the remainder still coming from glucose). The key concept in being able to conserve lean tissue such as protein during a fast is to decrease the dependence of the brain on glucose. Provision of ketone bodies achieves this goal.

This metabolic conversion has other benefits as well. In addition to providing an alternative fuel for energy generation for neurons, the metabolism of ketone bodies has a subtle impact upon neurotransmitter levels in the brain. As you may recall, neurotransmitters are the chemicals secreted by one neuron that bind to a neighboring neuron thus allowing them to communicate with each other. There are neurotransmitters that excite, or stimulate neurons, and others that relax or calm down neurons. They act in a yin-yang fashion to keep brain activity in the 'just right' zone. Glutamate is the excitatory transmitter and GABA (gamma amino butyric acid) is the inhibitory, or relaxing transmitter. The switch to ketones shifts this balance to a more relaxing mode. It is believed that this neurotransmitter modulation is one of the reasons a ketogenic diet is so effective in controlling pediatric epilepsy. It also is able to neutralize the stimulation generated by excessive calcium influx into neurons that occurs as we age. As intracellular calcium builds up in nerve cells it damages them. By shifting the GABA/Glutamate balance, this is minimized. Another unexpected benefit provided by the use of ketone bodies is an increase in the energy charge of neurons. What this means is that nerve cells have more energy to take advantage of.

In a prior article, I mentioned that one of the earliest findings detected in the brain of a person at risk for the development of Alzheimer's disease is a decrease in their brain's ability to efficiently use glucose. Ketone bodies are able to compensate for this. By administering a formulation containing MCT oil (medium chain triglycerides are turned into ketones) to subjects with Alzheimer's disease, researchers were able to improve mental functioning. These findings were reported in the medical journal Neurobiology of Aging (2004;25:311-314). This observation illustrates the power of ketones to beneficially impact brain function. What we all must remember is that dietary changes can generate ketones as effectively as MCT oil.