If you ask many people what the primary fuel for your brain
is they will most likely tell you that it is glucose. In fact many sources used to say that the brain could ONLY
use glucose as a fuel. However, it
has been known for some time that ketones are more efficient fuel source for
our brains. In fact this article says that
ketogenic diets have been used as a treatment for epilepsy since the
1920’s! And now, an even more
efficient fuel is being talked about: Lactate. Peter from Hyperlipid has a good
write up about a paper
that talks about the brain using lactate, and why he thinks it is such a good
fuel.
This is all well and good, I am all for feeding my brain the
most efficient fuels. If we
evolved primarily to support such big and “expensive” (energy consumption-wise)
brains this would seem a very important thing to do to maintain good overall
health. However, after reading all
this I am left wondering: How am I supposed to get all this lactate to feed my
brain? I can’t eat lactate. Also,
with all these fuels for our brain, is there an optimal ratio of fuels? Let’s take a look.
Well first of all I think it is important to take a look at
the different types of brain cells, as not all metabolize fuels equally, much
like the various other types of cells of our body don’t metabolize
equally. There are 4 main cell
types in your brain, divided into two categories, the neurons and the glial
cells. The neurons are the workhorses,
they actually transmit the electrical signals needed for brain function. But the glial cells are just as important. These cells are separated into three
types: astrocytes, oligodendrocytes, and microglia. Oligodendrocytes help to create the myelin sheath around our
neurons, while the microglia act similar to immune cells for the brain. Astrocytes are cells that help support
the brain in a variety of ways, from holding neurons in place to providing
nutrients. It seems that the
neurons are the primary consumer of lactate in our brains, with the glial cells
utilizing almost none of it (1, 2). So when we talk about lactate being a
more efficient fuel for our brain, we really mean our neurons, as the other
cells don’t appear to utilize it very effectively.
Now, how do I get all this lactate to feed my neurons? Since
lactate is mainly produced during exercise this is the time that our brain is
consuming most of it (3). However, hypoxia, or lack of oxygen in
the brain can also trigger lactate consumption (4). Lactate uptake
by our brains in determined by its concentrations in our blood, so we can see
one of the benefits of intense exercise: the production of lactate to fuel our
brain (5). This is one of the reasons why everyone
should be doing some form of intense aerobic exercise. This will help to create both a high
blood lactate concentration and a slightly hypoxic environment that will
further trigger lactate consumption by our brain.
The question of an optimal ratio of fuels for your brain is
a tricky one, as it seems like your brain has a natural pecking order of what
it would like to use, but will just take nutrients at will to meet its
need. This pecking order is
lactate> ketones> glucose> fats. Now the brain will use whatever is
around, and usually in most people that is glucose. But during times of high
energy usage by the brain it appears it actively takes in ketones or lactate to
fuel that high activity level. Not
only does it start to take in these ketones and lactate to fuel itself during
these energy intense times, it looks like if it finds some lactate it will
preferentially transport that over the ketones (6)!
So in summary, it does appear that lactate is a very good
substrate for our brains, and is probably its most preferred fuel. The best way to get lactate for your
brain is through high intensity aerobic activity. If you use your brain a lot it appears that it will
transport lactate and/or ketones to fuel this high activity level. Glucose appears to be a fall back fuel
for the brain, in case it can’t find any lactate or ketones around, or if it
isn’t revved up to perform some task.
With all this I would just make sure to get some good exercise, and make
sure to be eating your coconut oil for the very ketogenic medium-chain triglycerides
found within!
"This pecking order is lactate> ketones> glucose> fats. Now the brain will use whatever is around, and usually in most people that is glucose."
ReplyDeleteSome blogs and books that I read suggest that fats is a better fuel for the brain above glucose and therefore recommend lots of good fats (olive and coconut oil, avocados, salmon etc) and a verylow carbohydrate diet. They also recommend this as a way to produce these ketones for fuel. What say you ?
-Gerard
I have yet to find any significant sources that say that fatty acids can be metabolized by the brain, let alone be a better fuel than glucose or ketones. However, the amount of fat in the diet does appear to have a big effect on the brain. First, the brain is made mostly of fatty acids (http://www.jlr.org/content/6/4/537). So lots of good fats, especially the n-3 fats EPA and DHA, are very important for brain HEALTH, but don't get metabolized for energy. Also, intermediates of fatty acid metabolism appear to be important in signaling the bodies energy status to brain (http://www.ncbi.nlm.nih.gov/pubmed/18248603). Finally, like you mentioned consuming lots of good fats, and keeping carbohydrates low is an express route to ketone formation, which is a major energy source for the brain.
DeleteIntake of fat is clearly important to the overall health and function of our brain, without proper fat intake our brain wouldn't well at all. I think it is for these health benefits that many sources recommend lots of good fats, as they don't appear to be used as energy sources for the brain very often. It is important to note that not all tissues are created equally, and the rest of our tissues are able to metabolize any type of fat into energy. In fact, fat is most likely the preferred fuel for most of our other tissues, including muscle.
I thought the brain could only burn glucose, and that fats get converted to glucose when needed to fuel the brain? And with the ketones, doesn't your body have to be in ketosis in order to create ketones, and so you'd need to be on a high-fat diet to create them? And can it burn the ketones directly?
ReplyDeleteIs the lactate you describe a derivative of lactic acid,the waste product of your muscles after effort? That would be a pretty slick model, the waste product from exercise becomes the brains fuel.
The brain burning only glucose is an idea that has been purported for a very long time, but has only very recently been shown to be false.
DeleteThe creation of glucose from other substances in our body is known as gluconeogenesis, and the primary fuels for this are actually amino acids (protein) and not fat (http://en.wikipedia.org/wiki/Gluconeogenesis). As for fat being converted to glucose that is subject of hot debate. Many biochemistry texts will say that fats cannot be converted to glucose, but this is also untrue. It is a very long and complicated process but can be done. Most extra fat is either stored or, as you mentioned, converted to ketones which can be used as energy substrates in a variety of tissues, including the brain. Yes, a high fat diet is a good way to make ketones, you can also use high doses of medium chain triglycerides like coconut oil to create some ketones.
Finally, thanks to the satanic organic chemistry gods, lactic acid and lactate are the same thing for all intents and purposes, just a different name (http://en.wikipedia.org/wiki/Lactic_acid)!