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Nick Norwitz

@nicknorwitz

Jul 14

Omega-6/3 Ratio: What the Science Says about Mortality (🔗 in 5/6)

1/6) Perspective shapes everything. Sometimes, we can flip our viewpoint easily. But sometimes, the more informative lens takes effort to uncover. That’s what we’re going to do together in today’s newsletter — unpacking the story of Omega-3 and Omega-6 fats and why the ratio can be misleading.

As a brief primer: Omega-3 and Omega-6 fats are both essential nutrients — we need to consume them in our diets. However, the common belief is that, while both classes are essential, Omega-3s are “heart-healthy,” “brain-healthy,” and more is generally better for you.

Omega-6s, on the other hand, are considered easy to overconsume in modern diets, especially through processed foods and industrial seed oils. They can also be converted in the body into pro-inflammatory compounds.

What’s more, research consistently suggests that the balance between these fats matters. A lower Omega-6/3 ratio is associated with better health outcomes — including reduced cardiovascular risk and lower all-cause mortality.

So, it's understandable why many conclude: Eat more Omega-3s; Eat less Omega-6s; Improve your 6/3 ratio — and better health will follow. Sounds reasonable, right? Hold that thought.

And remember our theme: perspective. Because the full story of these fats is a more complex than the ratio alone might suggest.

2/6) In the study I want to review with you, researchers measured blood levels of Omega-6 and Omega-3 in 85,425 people and followed them for an average of 12.7 years. Over that period, 6,461 participants died of various causes. The researchers examined the association between fat levels and mortality — including the Omega-6/3 ratio.

They found that higher Omega-6/3 ratios were associated with a greater risk of death. Specifically, the highest quintile (median ratio of 14.8) exhibited a 26% increased risk of all-cause mortality relative to the lowest quintile (median ratio 5.9).

So once again, the conclusion seems clear: High Omega-6/3 ratio = bad. Lower ratio = good. Therefore, eat less Omega-6, more Omega-3, and you’ll optimize the ratio. Right? Well… not so fast…

3/6) Both Omega-6 and Omega-3 Associate with Better Outcomes

The researchers ran additional analyses — this time looking at Omega-6 and Omega-3 levels individually rather than as a ratio.

And the result? Both higher Omega-6 and higher Omega-3 levels were independently associated with lower all-cause mortality. In other words, more Omega-6 in the blood = better outcomes. More Omega-3 = better outcomes.

And the effects compounded!

The group with the highest Omega-3 and highest Omega-6 levels had the lowest mortality risk — a relative risk of just 0.48. That’s a 52% reduction in all-cause mortality.

So, higher circulating levels of both fats may be beneficial, but Omega-3 appears to have a stronger effect. When we analyze the ratio, it gives the impression that more Omega-6 in the body is worse; however, we are now starting to see how that story can be misleading.

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Nick Norwitz

@nicknorwitz

Jul 12

How Stress Steals Your Willpower – And How to Steal It Back (🔗in 4/4)

1/4) A new study, published in Nature, explores how chronic stress rewires the brain. It shows that stress shuts down flexible, goal-directed thinking and pushes us into rigid, automatic habits. Let’s break down how it works.

🧠DMS. - The Hub of Willpower🧠

The dorsomedial striatum (DMS) is a brain region that plays a central role in action–outcome learning and goal-directed behavior. For simplicity, think of the DMS as the brain’s hub for agency and willpower.

In fact, when DMS activity is suppressed, people tend to lose a sense of control — and fall into inflexible, often unhelpful, habits.

✌️Two Pathways: Learning vs. Habit.

The DMS sits at a crossroads of two pathways. The “Learning” pathway leads to flexible, thoughtful behavior, whereas the “Habit” pathway… well, that one is obvious.

🧠“Learning Pathway” The basolateral amygdala (BLA) activates the DMS, supporting action–outcome learning and goal-directed decision-making.

🧠 “Habit Pathway” - The central amygdala (CeA) sends inhibitory signals to the DMS, promoting automatic, rigid habit formation.

2/4) To summarize:

BLA → DMS = learning and flexibility. Think BL = Brain Learning.

CeA → DMS = habits and rigidity. Think Ce = Craving Enforcer.

😩Chronic Stress Turns the Dial Toward Habits😩

The researchers found that chronic stress weakens the Learning Pathway (BLA → DMS) and strengthens the Habit Pathway (CeA → DMS).

In their study, mice exposed to mild, unpredictable stressors — like a tilted cage, damp bedding, or mild foot shocks — started falling back on ingrained habits. They’d press a lever for food even after they were satiated, just because that’s what they were used to doing. Sound familiar?

3/4) The human equivalent is exactly what I’m sure you’ve experienced from time to time. I know I have. When we’re under chronic stress, that goal-oriented Learning Pathway (BLA → DMS) pathway gets dialed down — making it harder for us to connect our actions with their results. At the same time, stress activates the Habit Pathway (CeA → DMS) — this leads to repeating behaviors without thinking, even if they’re not helpful.
This all means less agency and more “Why did I just eat a tub of Chunk Monkey while watching Harry Potter until 1 am again?” moments.

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Nick Norwitz

@nicknorwitz

Jul 10

How Weighted Vests Trick Your Body into Losing Weight
(🔗 in 9/9)

1/9) Remarkable research is showing how mechanically loading your skeleton can toggle your brain to decrease hunger.

In today’s letter, I want to walk through three studies, including two human RCTs and a third study that blew me away!

2/9)👉Study #1 (RCT): Short-Term, Big Impact
In a proof-of-concept pilot trial, 72 participants with obesity were randomized to wear a weighted vest (11% body weight) or a non-weighted vest (1% body weight) eight hours per day for three weeks.

The study wearing the weighted vest resulted in statistically significant weight loss over just three weeks (1.61 kg). Furthermore, all of this weight loss was fat loss (-1.73 kg), with a +0.20 kg change in lean mass. Even for people with obesity, losing fat without losing (or maybe even gaining?) muscle over a short time period is impressive.

But this study was just three weeks. What happens if one were to wear a weighted vest for much longer?

3/9) Study #2 (RCT): Long-Term Weight Loss Defense

In another randomized controlled trial, participants were randomized to wear a weighted vest (~6 kg for 6.6 hours per day) for six months or to a control group. But this study came with two additional features.

First, during this six-month phase, both groups were placed on a strict, very low-calorie diet (1,100–1,300 Calories).

Second, all participants were then followed for an additional 18 months after the intervention ended. In other words, for 0–6 months people ate a very low-calorie diet with or without wearing a weighted vest; and then for 6–24 months people were left to live their lives freely without the weighted vest or a diet.

Both groups lost the same amount of weight during the initial six-month intervention, likely owing to the very restrictive nature of the diet. But what happened next was fascinating…

While the control group gained all their weight back, the weighted vest group only gained half the weight back.

In other words, weight regain was twice as much in the control group as compared to the weighted vest group after the intervention ended.

This suggests there was a ‘lingering’ metabolic effect of wearing the weighted vest. Weird? How? What’s going on?

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Nick Norwitz

@nicknorwitz

Jun 29

The Molecule Behind Exercise’s Anti-Aging Effects

*Today's letter (link in 6/6) reviews a new paper in @CellCellPress published 2 days ago. And includes a shoutout to someone special.

💪1/6) Nothing matches the health benefits of exercise. It’s the closest thing we have to a universal prescription for healthy aging.

But have you ever wondered how movement actually slows aging?

Movement isn’t magic. Exercise initiates a complex cascade of biochemical events that lead to adaptations designed to improve whole-body health. By identifying what those adaptations are, we can tap into the systems nature has evolved to optimize our health.

That’s the question the researchers behind today’s study explored. They weren’t trying to replace exercise — but they were curious if they could “bottle up” part of its benefits.

Method: In this study, 13 relatively sedentary men were instructed to exercise by running 5 kilometers — first every other day, then every day — for 25 days. The researchers measured a broad suite of metabolites in their bodies before and after the exercise regimen...

#exercise #healthspan #longevity #staycurious

2/6) Exercise is Good for you (and water is wet). But there’s more…

Exercise decreased markers of inflammation, including hsCRP and TNF-alpha, and increased so-called geroprotective(anti-aging) antioxidant proteins and pathways like Nrf2, SOD1, and Glutathione. These proteins and pathways help defend your body from oxidative stress — basically, the wear and tear that contributes to aging.

So, exercise is good for aging. No duh, right?!

But then the researchers dug deeper...

They wanted to know which metabolites were linked to these anti-inflammatory and geroprotective effects of exercise.

One molecule stood out — betaine.

3/6) Betaine Fights Aging at the Cellular Level

Betaine was originally discovered in beets — hence the name — and is also known as trimethylglycine. While betaine is easier to say, tri-methyl-glycine tells you exactly what it is: the amino acid glycine with three (tri) methyl groups attached to it. Fancy that — terminology that actually makes sense!

Betaine can be consumed through the diet as from beets (114-297 mg/100g) or spinach (600-645 mg/100g) or can be produced by the body. It plays a key role in metabolic pathways as a methyl donor and is generally thought to support cardiovascular health and physical performance.

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Nick Norwitz

@nicknorwitz

Jun 24

Untangling the Seed Oil Debate: ⚠️WARNING ⚠️Don’t Read If You Like Your Echo-Chamber
(🔗 at the end)

1/11) One of the most heated and fascinating debates in the nutrition space right now is that of “seed oils.”

It’s one of the keystone issues for the “Make America Healthy Again” #MAHA movement.

Robert F. Kennedy Jr., who calls the seed oils in which fast food chains now cook their French fries, “one of the most unhealthy ingredients we have in foods.”

This has led to a counterculture movement to replace industrialized plant-sourced fats, i.e., “seed oils,” with animal fats. There are cries to “Bring Back the Tallow Fries” to fast food chains like McDonald’s—the dietary version of “Make Fries Great Again.”

Up-front Acknowledgement

I spoke with several others composing this letter, including @drmarkhyman @paulsaladinomd @Physionic_PhD. Each provided references, input and/or feedback that was included in this letter in some form, and I look forward to ongoing conversations with each about this particularly controversial topic.

In fact, I’m releasing this letter now, rather than late July as originally planned, because I have a conversation planned with one of these men next week and thought community feedback would be ‘interesting’ fodder for our discussion.

The letter, should you choose to read it, may end up being a living document…

2/11) Restaurant chains are responding, literally “RFK’ing the fries,” meaning trading the seed oils for tallow for presumed health benefits.

But this isn’t really an issue or video about French fries. It’s about something much larger and more important.
It’s about how we dissect conflicting data in nutrition.

The reason there is such profound confusion on the topics of animal vs. plant fats and “seed oils” is because different sources of evidence make opposing arguments, and each side thinks their argument is best.

Rather than try to resolve the inconsistencies, we dismiss and bicker.

But in today’s letter, we try to dig into the details with data (nor dogma). This one is intense, but I hope you find it valuable.

3/11) Let’s start with a roadmap.
👉 I want to discuss the physiological rationale for why seed oil fries are presumed to be harmful, and why tallow fries might be better.
👉 Building on this French fry case in point, I want to expand the discussion to the human trial data on omega-6 fats and cardiovascular disease.
👉 Then, we will resolve the apparent contradictions that emerge.
👉 Finally, I’ll close by telling you what I think is practical and reasonable when it comes to handling fries, nuts, cooking fats, and making your food choices healthy (again?).

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Nick Norwitz

@nicknorwitz

Jun 21

Salmon Savvy: The Ultimate Guide to Choosing the Cleanest, Healthiest Fish

1/6) Salmon might wear the health halo, but not all salmon are created equal. Some are top-tier nutrition, and others are … well… toxic might not be an overstatement. Let’s talk fish fraud and how to avoid getting catfished at the seafood counter.

Let’s start with the elephant in the room—or manatee in the pool, as it were: farm-raised vs. wild salmon.

Is wild really better? YES.

The primary reason I always go wild over farm-raised is that farm-raised salmon tend to have much higher levels of chemicals like polychlorinated biphenyls (PCBs), pesticides, and dioxins, which largely derive from their feed and all of which have serious negative consequences on human health.

2/6) To take one of these as a representative example: dioxins, which are byproducts of various industrial processes such as burning waste, smelting metals, and bleaching. Some dioxins, like TCDD, are classified as Group I carcinogens (known to cause cancer in humans).

One study found that when eating farm-raised salmon, it would be easy to exceed the tolerable daily intake (TDI) of dioxins based on thresholds set by the World Health Organization. In some cases, as little as 4 servings of farm-raised salmon per month would push you past the dioxin TDI. By comparison, this analysis found that you could eat wild salmon every day (even twice per day!) and remain within safe levels of dioxin exposure.

What you’re seeing in the graph is the number of meals per month you’d need to eat of farm-raised salmon (white and light blue) or wild salmon (dark blue) to breach the safe intake limit. For farm-raised salmon, you can see only a handful of small servings will push you beyond the safe limit. But for wild salmon, they actually capped the analysis at “a practical consumption rate” of 60 meals/month.

3/6) Now let’s begin to revie some salmon types & terms. Most of the salmon you’ll see is Atlantic salmon, which is mostly farm-raised. These include Faroe Island, Norwegian, and Scottish, named for their geographic origins.

*Faroe Island salmon are often sold at restaurants at a premium price because they tend to be extra fatty and tasty. However, one credit I’ll give Faroe Island salmon is that they are generally raised without antibiotics.

*Norwegian salmon is quite common. About one-fifth of the salmon in the United States comes from Norway, and they are antibiotic-free 99% of the time.

*Scottish salmon. I don’t have much to say on these, although I’ve noted some scandals in the media. So, I suppose I’d just say so Scottish salmon are like a kilt… look traditional, but underneath it might be hiding something questionable.

(the difference you're seeing there is Faroe Island vs Alaskan Sockeye... to come)