Saturated fat: the making and unmaking of a scientific consensus (2022)

Posted by mgh2 10/26/2024

Saturated fat: the making and unmaking of a scientific consensus (2022)(journals.lww.com)

184 points | 424 commentspage 2

dang 10/26/2024|

Saturated fat: the making and unmaking of a scientific consensus - https://news.ycombinator.com/item?id=33942840 - Dec 2022 (6 comments)

latedoomer 10/29/2024||

The link between saturated fat and LDL cholesterol is extremely clear. Far from coming from low-quality studies, the relationship has been observed in RCT metabolic ward studies. The best data you can get on the acute effects of diet and we are talking hundreds of these experiments all observing the same relationship.

Does high LDL cause heart disease? That is probably less clear, I am not a scientist, so I really don't know what the latest is on this. LDL is present in Atherosclerotic plaques so it's not crazy to think it plays a role. If I was to guess, as a complete non-expert, low-fiber intake and inflammation probably play a role in turn LDL into atherosclerosis.

KempyKolibri 10/29/2024|

I’d say the evidence on LDL and atherosclerosis is even clearer than the SFA evidence. The EAS consensus paper is really good, I’d recommend giving it a read: https://academic.oup.com/eurheartj/article/38/32/2459/374510...

tuukkah 10/27/2024||

An alternative mechanism for how some foods deteriorate cardiovascular and brain health depends on how foods are cooked: https://en.wikipedia.org/wiki/Advanced_glycation_end-product

"Dietary advanced glycation products intake is associated with dementia" https://news.ycombinator.com/item?id=41209509

"A database for dietary AGEs and associated exposure assessment" https://news.ycombinator.com/item?id=41962796

ta988 10/27/2024|

AGEs could also simply be markers of poor lifestyle.

tuukkah 10/27/2024||

Sure, and especially if seared steaks and other high-dAGE foods are considered as a marker of poor lifestyle.

But if you are saying it's just correlation you're wrong, because the research has also described the mechanism. Wikipedia has a nice list of the effects: https://en.wikipedia.org/wiki/Advanced_glycation_end-product...

> "In the context of cardiovascular disease, AGEs can induce crosslinking of collagen, which can cause vascular stiffening and entrapment of low-density lipoprotein particles (LDL) in the artery walls. AGEs can also cause glycation of LDL which can promote its oxidation. Oxidized LDL is one of the major factors in the development of atherosclerosis."

> "AGEs have been implicated in Alzheimer's Disease,cardiovascular disease, and stroke. The mechanism by which AGEs induce damage is through a process called cross-linking that causes intracellular damage and apoptosis."

(AGE is a bad search term but the term glycotoxin is used as well.)

reissbaker 10/27/2024||

For me personally there's a very clear link between saturated fat and blood serum LDL and triglycerides: I had very high levels of both despite exercising regularly, switched to a low saturated fat diet with minimal other changes, and my LDL and triglycerides dropped enormously and are now in the "good" range. I don't know enough to know whether cholesterol actually increases heart disease risk, but for me personally there's a clear diet link between saturated fat and LDL cholesterol + triglycerides. YMMV! I suppose something else in the high saturated fat diet could have been causing the problem, but it certainly seems like a good proxy metric for me at least.

jodrellblank 10/30/2024||

> "switched to a low saturated fat diet with minimal other changes"

Does that mean switched fat to non-fat, or switched saturated fat to other types of fat? It seems that would be an important distinction for threads like this.

tonymet 10/27/2024||

It’s probably better off if we don’t give a handful of biased people control over the diets of millions. Maybe it is better to make decisions locally from personal connections. Maybe the transmission of knowledge through local groups had the positive effect of a sort of charcoal filter for knowledge. A bit of humility could be good for us. We spent all this time building and abusing a global authoritarian control network without ever considering the side effects.

krona 10/27/2024||

No mention of the French paradox:

> the paradoxical epidemiological observation that French people have a relatively low incidence of coronary heart disease (CHD), while having a diet relatively rich in saturated fats,[1] in apparent contradiction to the widely held belief that the high consumption of such fats is a risk factor for CHD.

https://en.wikipedia.org/wiki/French_paradox

chasebank 10/27/2024||

This is true for salt too.

"Intersalt, a large study published in 1988, compared sodium intake with blood pressure in subjects from 52 international research centers and found no relationship between sodium intake and the prevalence of hypertension. In fact, the population that ate the most salt, about 14 grams a day, had a lower median blood pressure than the population that ate the least, about 7.2 grams a day. In 2004 the Cochrane Collaboration, an international, independent, not-for-profit health care research organization funded in part by the U.S. Department of Health and Human Services, published a review of 11 salt-reduction trials. Over the long-term, low-salt diets, compared to normal diets, decreased systolic blood pressure (the top number in the blood pressure ratio) in healthy people by 1.1 millimeters of mercury (mmHg) and diastolic blood pressure (the bottom number) by 0.6 mmHg. That is like going from 120/80 to 119/79."

[0] https://www.scientificamerican.com/article/its-time-to-end-t...

alfiopuglisi 10/27/2024||

7.2 grams a day is still a lot. Low-sodium diets aim for less than 3 grams a day, and it is not that difficult to go even lower. Whether a near-zero sodium intake is good or not, it's another can of worms, but a study looking at a huge-salt diet vs. a high-salt diet does not look very useful.

tonymet 10/27/2024||

Before refrigeration sodium consumption was 10x

tonymet 10/27/2024|||

“The French paradox” is preposterous. Rather than re-assessing the “low fat” model, the approach was to call French nutrition a “paradox”. Resolving the paradox itself should have been done before presenting the low fat model as a fact.

paulpauper 10/27/2024||

I think it's a combination of low-stress lifestyle and demographics. Or differences of reporting. I am skeptical that there is a genotypical protection to heart disease unique to the French.

fwip 10/27/2024||

The claim is not that French people are resistant to heart disease. It is a datapoint that reality may not fit the "fat -> heart disease" model.

KempyKolibri 10/27/2024||

Yet within the French population, higher consumption of SFA is associated with higher CVD. So the French paradox doesn’t really seem to be any such thing.

naveen99 10/27/2024||

There is a u shape to ldl levels and longevity just like with bmi: https://pmc.ncbi.nlm.nih.gov/articles/PMC4908872/

By the guidelines nunbers, Low is worse than normal, “normal” is low, a little high is protective when you have other morbidities…

KempyKolibri 10/28/2024|

Because LDL drops when you have cancer, or a heart attack. That is, the U shape is a result of reverse causation. When you look at longitudinal data there’s no U shape - it’s straight as an arrow. Higher LDL-c -> more heart disease.

mgh2 10/26/2024||

*Original article submitted to HN: https://www.eviemagazine.com/post/american-heart-association...

dang 10/27/2024|

Yes, when we change the URL I almost always post the original link in the thread - I did that at https://news.ycombinator.com/item?id=41957788 but of course these things can get lost in the shuffle

gurjeet 10/26/2024||

TL;DR from the fine article:

Summary

The idea that saturated fats cause heart disease, called the diet-heart hypothesis, was introduced in the 1950s, based on weak, associational evidence. Subsequent clinical trials attempting to substantiate this hypothesis could never establish a causal link. However, these clinical-trial data were largely ignored for decades, until journalists brought them to light about a decade ago. Subsequent reexaminations of this evidence by nutrition experts have now been published in >20 review papers, which have largely concluded that saturated fats have no effect on cardiovascular disease, cardiovascular mortality or total mortality. The current challenge is for this new consensus on saturated fats to be recognized by policy makers, who, in the United States, have shown marked resistance to the introduction of the new evidence. In the case of the 2020 Dietary Guidelines, experts have been found even to deny their own evidence. The global re-evaluation of saturated fats that has occurred over the past decade implies that caps on these fats are not warranted and should no longer be part of national dietary guidelines. Conflicts of interest and longstanding biases stand in the way of updating dietary policy to reflect the current evidence.

loeg 10/27/2024|

Can't tldr this article without including the author's name and reputation, and that many of the representations made are false. In particular, this statement is false:

> [nutrition experts] have largely concluded that saturated fats have no effect on cardiovascular disease, cardiovascular mortality or total mortality

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