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Nick Norwitz

@nicknorwitz

Feb 1

🧠💤New Sleep Research Explores What Drives Clearance of Metabolic Waste when you Sleep & Raises 2 Interesting Question?

1/4) These new data in @CellCellPress identify a regulatory mechanism behind the “glymphatic system,” the waste removal system that operates in your brain when you sleep 🗑️

*Necessary Background*
Your brain is packed so full of neurons, support cells and blood vessels there isn’t space for the “lymphatic” system that operates throughout the rest of the body

Therefore, your brain as a “glymphatic” system (named for glia [brain support cells] + lymphatic)... Basically, constricting of blood vessels when brain's metabolic demands are lower (sleep) allows cerebral spinal fluid to rinse metabolic waste out of your brain when you sleep

But how does it work? ...

Ref, Cell Jan 8 2025. PMID: 39788123

cc @sleepdiplomat @hubermanlab - thoughts, see 4/4
#brainhealth #neuroscience #sleep

2/4) The hormone, norepinephrine (NE), is released by a region in the brainstem called the “Locus Coeruleus.”

NE is a vasoconstrictor and released in a pulsatile manner.

🌟Mechanism: In the brain, the researchers discover, the pulsatile release of NE from the Locus Coeruleus leads to rhythmic waves in brain blood vessels that enhancing glymphatic flow and, thus, increase the removal of metabolic waste as we sleep.🌟

Because buildup of metabolic waste is a key contributor to cognitive decline and neurodegenerative diseases, the major implication is that this system may be an essential mechanism employed during sleep to promote cognitive longevity.

3/4) They also show that the sleep medication, Zolpidem (Ambien), impairs the normal oscillations in NE and decreases glymphatic flow.

Thus, it’s possible long-term use could contribute to a build-up of metabolic debris in the brain.

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Nick Norwitz

@nicknorwitz

Jan 30

"Tunneling Nanotubes" in the Brain (Now with more mind-blowing detail 🤯)

1/5) Question⁉️: Could microscopic tunnels in your brain hold the secret to preventing Alzheimer’s and Parkinson’s?

Sounds like science fiction, right? But it’s real!

New study, published in @NeuroCellPress builds upon prior research about the fascinating topic of tunneling nanotubes, literal tunnels between cells – including cells of different types – that allow them to exchange internal components.

2/5) Why is this important for brain health?

In this study, the researchers looked specifically at tunneling nanotubes formed between neurons and microglia, the resident immune cells in the brain. Simply, microglia are the clean-up crew.

But, as we will find out, they are also much more than that.

Now, what they found first is that microglia can form tunneling nanotubes with neurons, and through these nanotubes suck up harmful protein aggregates that play roles in Alzheimer’s disease, tau, and Parkinson’s disease, alpha-synuclein.

The microglia use these nanotubes to suck these toxic proteins out of neurons, and then destroy them. Pretty amazing, right?

But that’s not all...

3/5) The microglia also replenish the mitochondria, donating healthy mitochondria to neurons through the nanotubes!

So, at a high level, imagine microglia extending one nanotube arm to suck out the poisonous proteins harming mitochondria and extending one nanotube arm to supply a new supply of fresh, healthy mitochondria. How incredible is that?!

And, indeed, they show in this study that this has functional consequences — with nanotubes formed between neurons and microglia leading to improvements in neuron metabolism, reduced oxidative stress, and better mitochondrial function when the neurons were metabolically challenged.

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Nick Norwitz

@nicknorwitz

Jan 22

Holy Cow! 😇🐮 Cheese May Actually Cut Cardiovascular Risk (links at the end)

1/5) A 2025 study including ~900,000 participants followed for ~9 million person-years found dairy – and especially cheese – intake was associated with reduced cardiovascular disease and stroke 🫀

Some quotes:
👉 “Total dairy consumption is associated with a 3.7% reduced risk of cardiovascular disease and a 6% reduced risk of stroke

👉Although cheese, especially hard cheese, is rich in salt, saturated fat, and calories, we still detected protective relationships for hard cheese and high-fat cheese...”

But(ter) it’s not so simple. If you watch the full video (link at the end), Brie prepared for nuance. You’ll have your mind Roqued. And I’ll churn out some Muenster puns along the Whey.

#cheese #hearthealth #puns

2/5) 🧀A few more highlights🧀

A complicating factor is that there are lots of different types of dairy. The researchers then did a breakdown based on dairy types, and found:

Cheese consumption was associated with lower cardiovascular disease risk, with a 12% decreased risk among those consuming cheese at least 7 times/week of cheese versus those consuming cheese less than 2 times/week.

The relationship between milk and yogurt (and ice cream) was less straight forward (see video for nuance notes).

3/5) 🤔Also, while in UK cohort more total dairy intake was associated with 7% lower rates of new cardiovascular disease and 14% lower risk of ischemic stroke… in the Chinese cohort, they found no association with cardiovascular disease after the multivariable adjustment, a 9% increased risk of coronary heart disease, but 6% lower risk of stroke…

Hmm. Weird?

Now, it’s not fully explained why this was the case, but there are at least two possibilities.

1. First, the average intake of total dairy products in the UK cohort was more than 4X higher than in the Chinese cohort. So, it is plausible that the cardiometabolic benefits of dairy consumption may require a relatively high level of intake. (Aside: I love this interpretation by the authors!)

2. Second, genetic differences between the populations may play a role, i.e. there may be something about the genetics of people in the UK that allow them to benefit more from dairy as compared to the population in China, as a whole.

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Nick Norwitz

@nicknorwitz

Jan 16

Layne’s 'Steaking' a Claim on #Carnivore. Let’s assess the rigor of his claims in a brief thread 🧵🥩👇

1/5) First, @BioLayne engages in ‘superficial citation bombing,’ a tactic whereby an influencer drops and bunch of references (here, in the form of pubmed IDs), without doing his due diligence to process the data. Here, he qualifies carnivore diet as extreme keto (and basically zero carb), but then cites studies where the ‘low-carb’ threshold is 40-45% kCal.

The meta-analysis he cites classified “low-carbohydrate diet” as ≤40% kCal from carbs with fat kCals as low as 30% (Table 1, PMID: 32238384)

Similarly, the Cochrane review he cites includes low-carb diets “< 45%” kCal from carbs.

There is a sub-section on ‘very-low carb diets’ (on which he does not comment). Largely, this was qualitative in the report.

But if you actually dig into the RCTs, you’ll note results like, “In a 12-month trial, adults with elevated HbA1c and body weight assigned to an low-carbohydrate ketogenic diet had greater reductions in HbA1c, lost more weight, and reduced more medications than those instructed to follow an moderate-carbohydrate, calorie-restricted, low-fat diet.” (PMID: 29269731)

This is par for the course with Layne. He once tried to dunk on me citating a paper where it was very clear he didn’t look at Figure 1.

*Note 1: I can't quote his Tweet because I remain blocked*

*Note 2: As I've made abundantly clear, I'm more than happy to engage in a long-form discussion / debate with Layne. He's declined every opportunity in the past.*

2/5) He calls a carnivore diet “unnecessary” and “not backed by any scientific evidence.”

But, as any good scientist should know, “absence of evidence is not evidence of absence.” Furthermore “necessary” deserves qualification. Let’s start with the latter.

Is a carnivore diet “necessary” to lose weight. No. Who said it was?

However, clinical reports (and case series, PMID: 39296504) suggest that for some patients a carnivore diet is ‘necessary’ (or uniquely beneficial) to keep their specific clinical conditions (e.g. inflammatory bowel disease) in remission.

Having met, interviewed and taken medical histories on these patients (including those with decades suffering with disease and trialing all form of immunomodulators etc., only to find relief with a carnivore diet), I feel comfortable for saying – yes – a carnivore diet may be ‘necessary’ for these patients to live a tolerable life.

Does that mean carnivore is the best diet? No.

Does it mean that fiber is bad for your average person? No.

But to sweep under the rug the metabolic use cases where a carnivore diet may prove uniquely beneficial is uncurious and anti-scientific.

Now, to the “absence of evidence is not evidence of absence” statement. It’s true, there aren’t RCTs on carnivore diet for X condition. Why? They haven’t been funded and run.

So to say “not backed by any scientific evidence” is technically true but overlooks the important and practical fact that “more research is needed” before a carnivore diet could be recommended as standard of care.

3/5) It does not take a PhD (a fact "Dr" Norton never misses a chance to flex, including in his recent thread) to evaluate what @BioLayne is doing. It's what he usually does: 'attack the other' to garner clicks and social media points rather than actually trying to engage on the issues with any degree of nuance.

For those who don't know, when I first began to engage with Layne I was optimistic I could get his to the table for a serious discussion about complex matters.

But, again and again, he avoided/declined long-form verbal engagement and instead opted for shallow one-sided attacks.

For more on my assessment of his behavioral patterns, you can start here: youtu.be/iZ4p1bCsUio

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Nick Norwitz

@nicknorwitz

Jan 10

🚨 BIG Paper and BIG Initiative, CME-Credits! 🚨

1/4) 🍩🦠 Today’s video covers breaking new research in Nature Metabolism about a Virus that Causes Food Addiction?!

But that’s not all! I’m proud to be collaborating with Metabolic Health Initiative—the ACCME-accredited medical education organization behind The Metabolic Health Summit @MetabolicSummit, and The Metabolic Link podcast. Together, we are working to get some of my content CME-accredited, including this video!

This creates an incentive for doctors to learn about metabolic health, as part of our broader efforts to Make Metabolic Health Mainstream! Read on, then Spread the Word!

2/4) Here's a review of findings in 4 Quick Points:
👉 A particular Microviridae virus can infect gut bacteria
👉 In so doing, the virus alters the metabolism of dopamine and serotonin precursors
👉 This is linked to changes in brain activity, on fMRI, and worse Food Addiction Scores
👉 "Fecal Viral Transplant" Experiments suggest a causal relationship between this virus and food addiction behavior

Thus, these data suggest an axis whereby a virus can contribute to the clinical signs of food addiction, a big step in demystifying the link between gut-brain and eating behavior

For details (and to hear from the senior author of this research), see link in 3/4

3/4) For more nuances, and to hear directly, from the senior author of this groundbreaking research, check out the full video, here:

Read 4 tweets

Nick Norwitz

@nicknorwitz

Jan 7

🍩🧬Carbs and Codons: Understand Your Genes to Defeat Obesity 🧬🍩

1/6) This thread 🧵 review Mendelian Randomization that supports the Carbohydrate Insulin Model (#CIM) of Obesity. Let's dive in!

Background on Terms: CIM and Mendelian Randomization👇

🍩 The CIM is a mechanistic model of obesity that works as follows: a high glycemic load diet (meaning one that tends to spike blood sugar and blood insulin levels more) gives a hormonal signal to the body (high insulin) to store energy as fat tissue.

In other words, energy (calories) come in, and they’re “triaged:” preferentially towards fat, rather than energy expenditure or lean tissue.

As a downstream consequence, energy expenditure goes down and hunger increases. Thus, while “calories in – calories out = weight change” and thermodynamics is maintained, the calorie imbalance is the result of a primary hormonal disturbance.

🧬 Mendelian Randomization

A method scientists use to study whether a certain factor (like insulin secretion) causes a particular outcome (in this case, obesity).

It relies on genetic variations (remember those 4 million variable genetics sites?) that are assigned randomly by nature’s genetic coin toss to uncover cause-and-effect relationships.

🚨Study Question

So, in this study, the researchers asked the question, “does carbohydrate-stimulated insulin secretion (the amount of insulin released in response to a carbohydrate load) predict obesity?”

ht/ @davidludwigmd cc @AdrianSotoMota @drjasonfung @drericwestman @DaveEDanna @realDaveFeldman @ChrisPalmerMD @janellison
#MendelianRandomization #Genetics #Lowcarb

2/6) In this study, they used MAGIC! No, actually, they relied on data from the Meta-Analysis of Glucose- and Insulin-related traits Consortium (MAGIC), a previously published meta-analyses on insulin secretion including 26,037 people.

They also used data from the United Kingdom Biobank (n =138,541), and a validation cohort, the Cardiology and Metabolic Patient Cohort study at Massachusetts General Hospital (n =1,675).

Using prior knowledge about variations in the human genome, they created genetic risk scores for the traits: (i) carbohydrate-stimulated insulin secretion (how much insulin a person secretes in response to carbs), and (ii) body mass index (BMI).

3/6) The researchers found a higher insulin release genetic risk scores did predict higher BMI.

In fact, they even tested slightly different insulin release genetic risk scores in different populations and consistently found - “Yes!” - more insulin release in response to carbs, as influenced by genetics, did predict a higher BMI.

This is consistent with the #CIM: where higher insulin release tells fat cells to store fat, leading to obesity. This puts calories in the passenger seat where a calorie imbalance results, not from “just eating too many calories,” but from the hormonally stimulated growth of fat cells.

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