Lactate fuels the human brain during exercise

@article{Quistorff2008LactateFT,
  title={Lactate fuels the human brain during exercise},
  author={Bj{\o}rn Quistorff and Niels H Secher and Johannes J van Lieshout},
  journal={The FASEB Journal},
  year={2008},
  volume={22},
  pages={3443 - 3449}
}
The human brain releases a small amount of lactate at rest, and even an increase in arterial blood lactate during anesthesia does not provoke a net cerebral lactate uptake. However, during cerebral activation associated with exercise involving a marked increase in plasma lactate, the brain takes up lactate in proportion to the arterial concentration. Cerebral lactate uptake, together with glucose uptake, is larger than the uptake accounted for by the concomitant O2 uptake, as reflected by the… 
Cerebral glucose and lactate consumption during cerebral activation by physical activity in humans
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TLDR
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Blood Lactate is an Important Energy Source for the Human Brain
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TLDR
Findings support brain tissue redox state and oxygenation as potential modulators of an increase in cerebral blood flow at the onset of exercise.
Effects of the exercise in the cerebral blood flow and metabolism. A review
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New studies are suggesting that as the intensity of exercise increases, the glucose uptake decreases in favour of an increase in the lactate uptake, and Hyperthermia may also play a major role in the cerebral regulation system, since it can provoke central fatigue as well as hypoglycaemia.
Lactate uptake by the injured human brain: evidence from an arteriovenous gradient and cerebral microdialysis study.
TLDR
Despite relatively high brain lactate compared with arterial lactate concentrations, the brain appears to up-regulate lactate transport into the brain after TBI, which may serve to satisfy greater demands for energy substrate from the brain following traumatic brain injury.
An Ultra-High Field Magnetic Resonance Spectroscopy Study of Post Exercise Lactate, Glutamate and Glutamine Change in the Human Brain
TLDR
The results of this experiment showed that vigorous exercise resulted in a significant increase in brain lactate, and a negative correlation between glutamate and a measure of fitness, which supports the hypothesis that peripherally derived lactate is taken up by the brain when available.
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