1

votes

A ketogenic diet increases the blood flow to the brain by 39%. What are the implications?

Answered on August 19, 2014
Created June 06, 2013 at 10:04 PM

Does anyone have any knowledge of why this happens, and whether this is a beneficial effect for healthy, normal people? Could it affect cognitive performance?

Here is the study: http://www.ncbi.nlm.nih.gov/pubmed/8967461

82166cc32b6cf26de33b69f58fb583b1

on June 08, 2013
at 10:22 AM

Restriction in this context usually means, "Removed from the diet." Whenever blood BHB rises, blood glucose usually falls. This is not restriction. It's part of the body's regulatory mechanisms.

Dd74e6399ae697d8603dc9aa74fbafae

(695)

on June 08, 2013
at 03:44 AM

As Bhb were injected, glucose dropped and this is equal to glucose redtriction in terms of cerebral metabolism. Which is what I ment.

Dd74e6399ae697d8603dc9aa74fbafae

(695)

on June 08, 2013
at 03:42 AM

This was in humans, not rats, which is why I find it so interesting. And while I could perform a test on my own, it's not the same as a true study. I am interested in the chemical changes, what happens inside the brain and how this may impact long term health, not just immediate changes in cognitive performance during problem solving.

82166cc32b6cf26de33b69f58fb583b1

on June 08, 2013
at 12:59 AM

Raydawg, of course fasting causes ketosis. But that doesn't mean that all of the effects of fasting and eucaloric ketogenic diets are the same. They aren't all the same.

82166cc32b6cf26de33b69f58fb583b1

on June 08, 2013
at 12:55 AM

Raydawg, of course fasting causes ketosis. But that doesn't mean that all of the physiological effects of fasting and eucaloric diets are the same. They aren't all the same.

82166cc32b6cf26de33b69f58fb583b1

on June 08, 2013
at 12:46 AM

Rawdawg, of course fasting causes ketosis. But that doesn't mean that all of the physiological effects of fasting are identical to the all of the physiological effects of eucaloric ketogenic diets. They aren't.

82166cc32b6cf26de33b69f58fb583b1

on June 08, 2013
at 12:08 AM

If you're saying that you'd like to find studies of cognitive performance in non-impaired humans on ketogenic diets, I agree. Such studies would be valuable. As I said a moment ago, this would be an easy thing to measure with self experiments. All you would need is a BHB meter, some test strips, a lancet, food, and one or more repeatable cognitive tests. Seth Robert's blog could be a model. http://blog.sethroberts.net/category/self-experimentation/

82166cc32b6cf26de33b69f58fb583b1

on June 08, 2013
at 12:04 AM

If you are saying that you would like to find studies of cognitive performance in non-impaired humans on ketogenic diets, I agree. Such studies would be valuable. But I haven't seen any. As I said a moment ago, this would be an easy thing to measure with self experiments. All you would need is a BHB meter, some test strips, a lancet, food, and one or more repeatable cognitive tests. Seth Robert's blog could be a model.

82166cc32b6cf26de33b69f58fb583b1

on June 07, 2013
at 11:40 PM

If you are saying that you would like to find studies of cognitive performance in humans on ketogenic diets, I agree. Such studies would be valuable. But I haven't seen any. As I said a moment ago, this would be an easy thing to measure with self experiments. All you would need is a BHB meter, some test strips, and one or more repeatable cognitive tests. Seth Robert's blog could be a model. http://blog.sethroberts.net/category/self-experimentation/

82166cc32b6cf26de33b69f58fb583b1

on June 07, 2013
at 11:34 PM

Sorry, I don't have the paper, only the abstract, and I made the wrong inference from its first sentence. But based on what you tell me here, they didn't restrict glucose. They only injected (I assume) BHB into (I assume) rats. (Btw rats are questionable models for human ketosis.) Glucose usually falls when BHB rises but that's not restriction. If we want to know about the effect of raised BHB on cognitive performance in healthy subjects, then we need to measure cognitive performance in healthy subjects with raised BHB. This would be an easy thing to self test. Maybe you should do it.

Dd74e6399ae697d8603dc9aa74fbafae

(695)

on June 07, 2013
at 05:06 PM

It does say "during starvation", however, it would be more correct to say during glucose restriction, as this study did not at all involve starvation. They directly injected ketones. I know that oxygen consumption remain unchanged, and I did not expect anything else. What I am curious about is whether increased blood flow could increase nutrient availability and prevent degeneration in healthy subjects. Ketosis does seem to have very good effect on those with the degenerative diseases, but I have not seen studies on healthy subjects, and thus wondered what effects these results could have.

96440612cf0fcf366bf5ad8f776fca84

(19463)

on June 07, 2013
at 04:33 PM

+1 exactly what I was gonna say.

96440612cf0fcf366bf5ad8f776fca84

(19463)

on June 07, 2013
at 04:28 PM

Unless you have no fat stores left, or are not adapted to burning ketones, when you're fasting, you should be in ketosis once you deplete enough of your glucose stores in muscle/liver.

96440612cf0fcf366bf5ad8f776fca84

(19463)

on June 07, 2013
at 04:19 PM

Awesome unexpected benefit. Evolutionarily it makes sense. If you're hungry/starving, you need your brain to be able to hunt prey.

De1095b2ba29c1035f00428cbfe3cc7c

(777)

on June 06, 2013
at 10:52 PM

interesting, it makes me think about people consistently reporting brain fog being replaced by clarity, for something like that to happen you would could infer there must be some kind of biological activiy going on, increased blood flow to the brain makes sense

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on June 06, 2013
at 10:22 PM

don't believe me? Gather together a bunch of anorexics and have them piss on a keto stick for you. Look at their bulging muscles and lean ripped physiques. Sex drives of a 17 year old on steroids.

1edb06ded9ccf098a4517ca4a7a34ebc

(14952)

on June 06, 2013
at 10:20 PM

Cold hands and feet. Reduced blood flow to muscles. Reduced muscle recovery and gains. Reduced blood flow to other organs. Possible erectile dysfunction. When you're starving (and that's what a keto diet simulates), certain biological functions get put in the queue. No need to worry about getting jacked and ripped and making babies when you're starving. (a hypercaloric keto diet is still simulating starvation, as keto IS a starvation response designed to slow metabolic rate and keep you alive longer).

  • Dd74e6399ae697d8603dc9aa74fbafae

    asked by

    (695)
  • Views
    6.9K
  • Last Activity
    1460D AGO
Frontpage book

Get FREE instant access to our Paleo For Beginners Guide & 15 FREE Recipes!

2 Answers

4
82166cc32b6cf26de33b69f58fb583b1

on June 07, 2013
at 12:35 AM

A ketogenic diet increases the blood flow...Could it affect cognitive performance?

This study is about fasting, not ketogenic diet. The first two words of the abstract you linked are, "During starvation."

But let's assume that we can extrapolate these results to ketosis caused by diet. This study found (and other studies have found also) that when ketosis raises cerebral blood flow, the brain's oxygen consumption (an indicator of energy use) remains the same.

Given the unchanged energy use I don't see any reason to suppose based on this study and other ketosis blood flow studies that cognitive performance increases.

However, we know from other kinds of studies that ketosis can increase cognitive performance under certain conditions. And many people report that they feel mentally sharper when they are in elevated ketosis.

Could it affect cognitive performance?

In order to answer this question we have to look at cognitive tests, not measurements of blood flow.

Here are two examples of papers that answer your question.

http://www.ncbi.nlm.nih.gov/pubmed/20204773

http://www.ncbi.nlm.nih.gov/pubmed/21130529?dopt=AbstractPlus

82166cc32b6cf26de33b69f58fb583b1

on June 08, 2013
at 12:04 AM

If you are saying that you would like to find studies of cognitive performance in non-impaired humans on ketogenic diets, I agree. Such studies would be valuable. But I haven't seen any. As I said a moment ago, this would be an easy thing to measure with self experiments. All you would need is a BHB meter, some test strips, a lancet, food, and one or more repeatable cognitive tests. Seth Robert's blog could be a model.

82166cc32b6cf26de33b69f58fb583b1

on June 08, 2013
at 12:08 AM

If you're saying that you'd like to find studies of cognitive performance in non-impaired humans on ketogenic diets, I agree. Such studies would be valuable. As I said a moment ago, this would be an easy thing to measure with self experiments. All you would need is a BHB meter, some test strips, a lancet, food, and one or more repeatable cognitive tests. Seth Robert's blog could be a model. http://blog.sethroberts.net/category/self-experimentation/

Dd74e6399ae697d8603dc9aa74fbafae

(695)

on June 07, 2013
at 05:06 PM

It does say "during starvation", however, it would be more correct to say during glucose restriction, as this study did not at all involve starvation. They directly injected ketones. I know that oxygen consumption remain unchanged, and I did not expect anything else. What I am curious about is whether increased blood flow could increase nutrient availability and prevent degeneration in healthy subjects. Ketosis does seem to have very good effect on those with the degenerative diseases, but I have not seen studies on healthy subjects, and thus wondered what effects these results could have.

Dd74e6399ae697d8603dc9aa74fbafae

(695)

on June 08, 2013
at 03:44 AM

As Bhb were injected, glucose dropped and this is equal to glucose redtriction in terms of cerebral metabolism. Which is what I ment.

82166cc32b6cf26de33b69f58fb583b1

on June 08, 2013
at 12:46 AM

Rawdawg, of course fasting causes ketosis. But that doesn't mean that all of the physiological effects of fasting are identical to the all of the physiological effects of eucaloric ketogenic diets. They aren't.

Dd74e6399ae697d8603dc9aa74fbafae

(695)

on June 08, 2013
at 03:42 AM

This was in humans, not rats, which is why I find it so interesting. And while I could perform a test on my own, it's not the same as a true study. I am interested in the chemical changes, what happens inside the brain and how this may impact long term health, not just immediate changes in cognitive performance during problem solving.

82166cc32b6cf26de33b69f58fb583b1

on June 07, 2013
at 11:34 PM

Sorry, I don't have the paper, only the abstract, and I made the wrong inference from its first sentence. But based on what you tell me here, they didn't restrict glucose. They only injected (I assume) BHB into (I assume) rats. (Btw rats are questionable models for human ketosis.) Glucose usually falls when BHB rises but that's not restriction. If we want to know about the effect of raised BHB on cognitive performance in healthy subjects, then we need to measure cognitive performance in healthy subjects with raised BHB. This would be an easy thing to self test. Maybe you should do it.

82166cc32b6cf26de33b69f58fb583b1

on June 08, 2013
at 10:22 AM

Restriction in this context usually means, "Removed from the diet." Whenever blood BHB rises, blood glucose usually falls. This is not restriction. It's part of the body's regulatory mechanisms.

82166cc32b6cf26de33b69f58fb583b1

on June 07, 2013
at 11:40 PM

If you are saying that you would like to find studies of cognitive performance in humans on ketogenic diets, I agree. Such studies would be valuable. But I haven't seen any. As I said a moment ago, this would be an easy thing to measure with self experiments. All you would need is a BHB meter, some test strips, and one or more repeatable cognitive tests. Seth Robert's blog could be a model. http://blog.sethroberts.net/category/self-experimentation/

82166cc32b6cf26de33b69f58fb583b1

on June 08, 2013
at 12:59 AM

Raydawg, of course fasting causes ketosis. But that doesn't mean that all of the effects of fasting and eucaloric ketogenic diets are the same. They aren't all the same.

96440612cf0fcf366bf5ad8f776fca84

(19463)

on June 07, 2013
at 04:28 PM

Unless you have no fat stores left, or are not adapted to burning ketones, when you're fasting, you should be in ketosis once you deplete enough of your glucose stores in muscle/liver.

82166cc32b6cf26de33b69f58fb583b1

on June 08, 2013
at 12:55 AM

Raydawg, of course fasting causes ketosis. But that doesn't mean that all of the physiological effects of fasting and eucaloric diets are the same. They aren't all the same.

1
Medium avatar

(2338)

on June 07, 2013
at 12:45 AM

Looking at it from an evolutionary perspective it makes some sense. When cave people went into ketosis food was likely very scarce and they need their brains more than ever to help them find food so the body produces ketones which by some mechanism bring more blood into the brain. I notice this also in my life, I get very lucid either when fasting or low carb. The problem is it doesnt last indefinitely at some point I always crash. I also notice when I eat more carbs I daydream and get lost in my head much easier. Ketosis can obviously be very beneficial but it's application for different people is very individual. Nothing a little n=1 experiment can't figure out.

96440612cf0fcf366bf5ad8f776fca84

(19463)

on June 07, 2013
at 04:33 PM

+1 exactly what I was gonna say.

Answer Question


Get FREE instant access to our
Paleo For Beginners Guide & 15 FREE Recipes!