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There are lots of good reasons to try

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and follow a healthier diet. You

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lose weight, you feel good, but the

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main reason? To live

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a longer, happier, more productive

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life. Welcome to

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the Nutrition Facts Podcast. I'm your host,

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Dr. Michael Greger. Today

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we look at how the

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brain's detox mechanism works, the

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glymphatic system, and more

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importantly, what we can do to make it work

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even better. The glymphatic

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system is a newly discovered drainage

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system in the brain that

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clears the brain of toxic

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waste byproducts. Sleep is

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a great mystery. A

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treat shared across animal species, sleep

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must be of vital importance to

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survive natural selection pressures to eliminate

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such a vulnerable state. Indeed,

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cringe-worthy experiments have shown

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that keeping animals awake long enough can

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be fatal within 11 to 32 days. It

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turns out sleep is

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of the brain, by the brain, and

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for the brain. One function

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of sleep that has been elucidated in recent years

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is the clearance of toxic waste

1:11

byproducts through a newly discovered

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drainage system in the brain. With the

1:15

invention of the encephalogram, EEG, to measure

1:18

brainwave activity, the scientific world was quickly

1:20

disabused of the notion that sleep was

1:22

a time of rest for the brain.

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During certain stages of sleep, there

1:27

was brain-wide activity going on, but

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what was the brain actively doing?

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More than 2,000 years ago,

1:35

Aristotle proposed that sleep helps

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the body clean the blood, while

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today we know sleep may help

1:42

the body clean the brain. Until

1:45

2012, we thought that the brain

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was singular among organs for recycling nearly

1:50

all of its own waste. It

1:52

had to, since it was separated from the

1:54

rest of the body by the blood-brain barrier.

1:57

But the barrier that keeps toxins out of the brain. The

2:00

brain presumably keeps Doc Sons

2:02

in. Then. In

2:05

two thousand and twelve a brain

2:07

wine fluid friends port network was

2:09

discovered. turn the. Lymphatic

2:11

system. By. Microscopically

2:13

tracking dye injected in the brains

2:16

of my scientists discovered flawed so

2:18

tunnels surrounding blood vessels in the

2:20

brain. The pressure wave of arterial

2:22

pulses with every heart milks the

2:25

fluid a long before eventually dream

2:27

into the cerebral spinal the was

2:29

running the brain. Was

2:32

does this have to do is sleep? The.

2:34

Whole system is only really

2:36

do when sleeping during wakefulness.

2:39

these tunnels or clamp down

2:41

reducing lymphatic slow by ninety

2:43

percent. Of. The side

2:45

is a fluid, ships might interfere

2:47

with targeted neurotransmitter chemical communication and

2:50

the a week states have a

2:52

biological need for sleep. May.

2:54

Reflect the need for the brain to

2:56

enter into a state to filter up

2:59

it isn't neurotoxic waste products like beta

3:01

amyloid which is implicated in also armies

3:03

disease. Perhaps. This

3:05

could help explain why those who

3:08

routinely get fewer than seven hours

3:10

of sleep a night are at

3:12

increased risk of developing cognitive disorders

3:14

such as dementia. Randomized individuals to

3:17

have her sleep disrupted, a series

3:19

of beeps administered zoo and phones

3:21

in the sleep lab increases amyloid

3:24

levels whereas improving sleep by. Treating.

3:26

Sleep apnea. Patients with see bad

3:29

for example improve slow wave activity

3:31

deep sleep. And. Averse to lower

3:33

amyloid levels. Pet. Scans show

3:35

even a single all nighter to

3:38

cause significant increase in accumulation of

3:40

beta, amyloid, and critical brain areas.

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The problem. Is. Dead

3:45

Glum Santa Green filtration pierced and

3:47

dixon line with age. Old.

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Vice only have ten to twenty percent

3:52

a good verdict Function of young mice.

3:55

This. could be due to a number of

3:57

factors as we age we experienced less of

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the beeps low-wave sleep, the type of

4:01

sleep during which brain waste clearance appears

4:03

to be the most active, further

4:06

contributing to the stagnancy. Our

4:09

arteries tend to stiffen as we

4:11

age, reducing the pulsations that drive

4:13

the climatic pump. That

4:16

also offers one potential explanation as to

4:18

why hypertension is tied to dementia. The

4:20

thickening of artery walls with high blood

4:22

pressure also has a stiffening effect. How

4:25

can we counter this age-related,

4:28

glymphatic decline and keep our

4:30

brains cleaner? We'll explore

4:32

just that question next. What

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can we do to prevent the decline

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in glymphatic brain filtration as we age?

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Let's find out. Other

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than getting enough sleep, what

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can we do to improve the glymphatic clearance

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of waste from our brains? The

4:51

provision of a running wheel so

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mice could voluntarily exercise has been

4:56

shown to improve glymphatic clearance in

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aging mice, which was accompanied by

5:00

a reduced buildup of amyloid deposits

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and improved cognition. Sleeping

5:05

position may also make a difference.

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Studies on rats show that their natural

5:10

sleeping position curled up on their sides

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allows for better glymphatic transport than sleeping

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on their backs or stomachs. People

5:18

also tend to spend most of their

5:20

time sleeping on their side, particularly their

5:23

right side versus left, compared

5:25

to their backs or stomachs. This

5:27

may maximize blood outflow from the

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brain. When we sleep

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on our right side, our right internal jugular

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vein, the main blood vessel in our neck

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draining blood from the head, is

5:38

wide open, and our left jugular

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is partially collapsed and vice versa.

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Since most people have a dominant

5:46

right jugular vein, sleeping on their

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right side might maximize brain drainage.

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Does it matter? Well, people

5:53

with neurodegenerative disease, mostly

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mild cognitive impairment, and Alzheimer's disease,

5:58

tend to sleep more on their back. their backs than

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those with normal cognition. About

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72% spend at least two hours a night on

6:05

their backs compared to 37% of

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those with healthier brains, raising

6:10

the intriguing possibility that

6:13

head position during sleep

6:15

could influence the clearing of neurotoxic

6:17

proteins from the brain. In

6:20

crib death, sudden infant death

6:22

syndrome, sleeping position

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can be a lifesaver, leading to

6:27

slogans like back to sleep or

6:29

more morbidly, face up to

6:32

wake up. It's premature for

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an adult jingle, maybe

6:36

on your flank to not draw

6:38

a blank. The

6:40

characteristic position of poor sleepers is

6:43

on their back though, so maybe

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it's the poor sleeping rather than the

6:47

position per se that leads to cognitive

6:49

decline or the causality

6:51

could be reversed with dementia deteriorating

6:54

good sleep habits. Even

6:56

if sleeping position did matter, it

6:59

may take a night in a

7:01

sleep lab to track your movement.

7:03

It turns out self-reported sleep positions

7:05

are often false. Should

7:07

brain benefits to side sleeping ever

7:10

be established, you can train yourself

7:12

with so-called positional therapies such as

7:14

the tennis ball technique,

7:16

which involves wearing a shirt to

7:18

bed backwards with a ball stuffed

7:21

in the chest pocket. The

7:23

uncertainties don't end with sleeping

7:26

position. The glymphatic

7:28

mechanism itself was rapidly embraced

7:30

in scientific circles and the

7:33

popular press. However, it's been

7:35

controversial. It wasn't until 2019

7:38

that the first evidence was published

7:40

that the glymphatic system discovered in

7:42

rodents even existed in human brain.

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Even the relationship between sleep and Alzheimer's

7:48

disease is perhaps best summed up

7:50

in a recent neurology review entitled,

7:53

It's Complicated. Yes, those

7:55

getting less than seven hours of sleep may

7:58

have high rates of Alzheimer's, In.

8:00

More. Than eight. Or.

8:02

Higher risk to. If. Anything

8:04

Population studies show that longer sleep

8:06

duration more than eight or nine

8:09

hours. Or. More strongly linked to

8:11

all summers disease and dementia in general

8:13

the sleeping less than five or six

8:15

hours. The. Association between

8:17

dementia and long sleep duration.

8:20

Could. Be reverse causation work Pro

8:22

grumbled changes in the brain

8:24

years before also is diagnosed.

8:26

causes prolonged sleep. Long.

8:29

Sleep duration may also just be

8:31

a confounding factor, a marker, some

8:33

underlying health problems that the real

8:35

culprit. For. Example oversleeping may be

8:38

a sign of depression, which itself

8:40

is an established risk factor for

8:42

dimension. But. There

8:44

is a plausible biological

8:46

mechanism for our extended

8:48

sleep duration. Could increase

8:50

dementia risk directly. Longer.

8:52

Sleep Duration: Typically defined as sleeping more

8:54

than eight hours a night. His.

8:57

Associate with some is of

8:59

systemic inflammation, elevated levels. Of.

9:01

Syria to protein and into would

9:04

consist. Of. Who Both of those

9:06

inflammatory markers in turn are so say

9:08

will increase in the risk. So.

9:11

Much more needs to be tease out about

9:13

the role of the democratic system before we

9:15

make conscious efforts to tweak it. We

9:18

would all love it if you could

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share with us your stories are reinventing

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your help to evidence based nutrition. Got

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a New Jersey Reverse that our Slush

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testimonials we may be able to shared

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on social media to help inspire others

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to see any graphs, charts, graphic images

9:34

are studies mentioned here. Please go to

9:36

the Nutrition Facts Podcast landing page there

9:38

you'll find all the detailed information need

9:40

plus links to other sources. respect for

9:43

each of these topics. My latest What

9:45

How Not The Age is Out Now

9:47

which premiered. At number two on

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the New York Times bestseller list.

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Check it out or your local

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public library. Of course all the

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books goes directly to charity. New.

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