Researchers in Denmark and The Netherlands have discovered that during exercise, the human brain shifts into a higher gear and uses an “alternative energy” source: it does not feed on glucose but on lactate.
The research was the work of corresponding author Johannes J. Van Lieshout of the University of Amsterdam, and colleagues, and is published in the October 2008 print issue of The FASEB Journal (The journal of the Federation of American Societies for Experimental Biology).
Up to a certain level of exercise, such as walking and light jogging, our muscles and other cells of the body get energy from aerobic respiration, that is glucose is oxidized by oxygen to make ATP molecules that deliver units of energy to cells.
But above a certain level of exercise, as it becomes more strenuous, the muscles shift to another way of making energy, using anerobic respiration, which involves lactate production and does not use oxygen.
Apparently, this study showed that like our muscles, our brains work harder during strenuous exercise and run on lactate not glucose, a finding that may help to explain why the brain continues to function well at a time of high demand for fuel and oxygen throughout the body.
The researchers showed not only that the brain runs on lactate during exercise but it actually shifts into a higher gear in terms of activity. They said the finding will open up new areas of brain research that will seek to understand what lactate does to the brain.
FASEB’s editor in chief, Dr Gerald Weissmann said:
“Now that we know the brain can run on lactate, so to speak, future studies should show us when to use lactate as part of a treatment.”
“From an evolutionary perspective”, said Weissmannm, “the result of this study is a no-brainer. Imagine what could have or did happen to all of the organisms that lost their wits along with their glucose when running from predators. They were obviously a light snack for the animals able to use lactate.”
For the study, Van Lieshout and colleagues reviewed studies that examined blood going to and from the brains of volunteers while they underwent strenuous exercise.
They found that blood going to the brain was higher in lactate than blood leaving the brain. And they found that the brain was not storing the lactate but using it as fuel, and also by clearing it from the bloodstream it was giving the muscles greater opportunity to use the glucose path.
The finding challenges a long held view that the brain is strictly a glucose fuel burner and that only the muscles switch to the lactate alternative. It also adds weight to the idea that lactate is not just a toxic byproduct of exercise, but a rich supplemental source of energy and that the body has sophisticated mechanisms for optimising where it gets energy from.
“Lactate fuels the human brain during exercise.”
Bjørn Quistorff, Niels H. Secher, and Johannes J. Van Lieshout.
The FASEB Journal. 2008 22: 3443-3449.
Written by: Catharine Paddock, PhD.