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 Usually, energy for muscle cells comes from carbohydrates or fat,
but when those fuels aren’t available and the body is in “starvation
mode” the liver will break down fat stores into ketones to use as
fuel.
Ketosis, or production of ketones by the liver, "is a natural
response to energy crisis and is of vital importance to us as it
allows us to survive 'insults' such as starvation and even the first
few hours after birth when fuel levels are low,” said lead author
Pete J. Cox of the University of Oxford in the UK.
In the new study, researchers found that when ketones are provided
in a drink, the body will use them for muscle fuel. Ketone-powered
workouts resulted in less lactate, a byproduct of breaking down
sugar that causes muscle cramps and soreness.
The researchers studied 39 high-level athletes, including former
Olympic cyclists, to see how their metabolism changed after
consuming the ketone drink and exercising.
Ketone uptake in the muscles increased as exercise got more intense.
In long-distance workouts, muscles used more ketones as fuel rather
than breaking down glucose. But in short bursts of high-intensity
work, like sprints, muscles work anaerobically – without oxygen –
and can’t use ketones as fuel, since ketones can’t be broken down
without oxygen.
To examine athletic performance, eight athletes fasted overnight
before completing two bicycle exercise trials of one-hour
steady-state cycling and a 30-minute time trial. For one trial, the
cyclists drank a carbohydrate drink, and for another they had a
drink with carbohydrates and ketones.
After the ketone drink, the cyclists traveled an average of 411
meters further in the half-hour time trial than after the
carbohydrate drink, as reported in Cell Metabolism.
“Hopefully this finding will help many athletes realize that optimum
fueling for sport is not simply to ingest as much carbohydrate as
possible - before, during and after exercise,” said Timothy Noakes
of the University of Cape Town in South Africa, who was not part of
the new study.
Most athletes will perform better by simply training more and eating
fewer carbohydrates, Noakes told Reuters Health by email.
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Safety studies have found no adverse effects of the ketone drink,
but “taking excessive amounts of ketones from any source (i.e. more
than the normal physiological levels our body is designed to cope
with) can alter the acid balance of the body and this is not
advisable,” Cox said.
“Currently the drink is not commercially available, and is difficult
to make even in a laboratory (patent protected), meaning it may be
some time before this drink, or ones like it can be made readily
available to the public,” he said.
A University of Oxford company is now developing the ketone fuel to
be commercially available later this year and the authors of the
study may receive royalties from its sale.
It is still unclear whether the effects are greater in trained
athletes, he said.
For the average athlete, the potential benefits of the drink are
probably too small to be worth the effort, Noakes said.
Cox told Reuters Health by email that being able to switch the body
to using ketones may be beneficial in certain settings, such as when
patients need to sustain function in disease.
SOURCE: http://bit.ly/2avFDHR Cell Metabolism, online July 27, 2016.
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