Thanks for this episode. A few months ago a colleague tried to warn me of the dangers of seed oils, which prompted me to look at the evidence. I found the same sort of studies as you, and reached the same conclusions.
A note on the Sydney Diet Heart Study. As you note, this is something of an outlier. A reason may be that the margarine content of the diet was not straight safflower oil but instead a mixture of safflower oil with trans fat-containing hydrogenated oils. (https://www.bmj.com/content/346/bmj.e8707/rr/629609) The trans fat content may help to explain the association with harm in that study. It may also limit the relevance of that study to foods in 2025, when trans fats are generally avoided by manufacturers.
You make it sound like the 21% reduction for CV event in the 2020 Cochrane review is a small benefit compared to the ask, using the NNTT of 56 to prevent one event in 4 years.
However, most of the included studies have relatively young populations (at a glance, median of the average age must be ~55) which is way before CV events peak.
It's not exactly shocking you would need to treat many 55 yos to prevent CV events because they hardly get them in the first place, even when the inclusion criterias often use some risk factor.
On the flipside:
1/ if you've gone and swapped sat fats out for 4 years it's probably rather painless to keep the diet at vitam
2/ the standard model CVD risk is that LDL cholesterol is a cumulative risk. That is, the longer it's elevated the more risk you accrue. Suppressing it even if only for 4 years is due to have lifelong benefits even if diminishing over time
The 21% RR over 4 years figure is a scientific construct but I therefore don't think it makes much sense to use it in a practical discussion. It's more helpful to frame it as evidence that suppressing sat fats will lead to postponing CV events in those who would experience it.
I'm surprised trans fats weren't addressed. The current concerns about seed oils feel directly connected to the past trans fat debacle. Public health officials advocated for trans fats as a replacement for saturated fats in the 70s and 80s, only for them to be proven highly detrimental. (Perhaps this warrants a separate discussion?) This history makes it difficult to trust public health messaging on seed oils. Furthermore, the fact that seed oils were hydrogenated to create trans fats, primarily to extend shelf life, complicates the effort to convince the public that seed oils are now safe.
>In the 1980s, some scientists began to associate heart disease with saturated fats, and in response, groups such as the Center for Science in the Public Interest and the National Heart Savers Association (NHSA) began to hound manufacturers for “poisoning America ... by using saturated fats,” and as a result “nearly all targeted firms responded by replacing saturated fats with trans fats,” as David Schleifer wrote in 2012 for the journal Technology and Culture.
I think it would be better if more people acknowledged that doing good nutrition science is complicated and difficult. That's why I like this show. Changing recommendations based on better evidence is a good thing, and it should make people feel more confident in our public health institutions, not less.
I can’t believe you weren’t aware that ‘piyu effay’ is an extremely offensive slur against bisexuals in much of Clackmannanshire. You’ve let the podcast down, you’ve let Stuart down, but most of all, you’ve let yourself down.
Thanks for this episode. A few months ago a colleague tried to warn me of the dangers of seed oils, which prompted me to look at the evidence. I found the same sort of studies as you, and reached the same conclusions.
A note on the Sydney Diet Heart Study. As you note, this is something of an outlier. A reason may be that the margarine content of the diet was not straight safflower oil but instead a mixture of safflower oil with trans fat-containing hydrogenated oils. (https://www.bmj.com/content/346/bmj.e8707/rr/629609) The trans fat content may help to explain the association with harm in that study. It may also limit the relevance of that study to foods in 2025, when trans fats are generally avoided by manufacturers.
I'd like to offer a bit of a quibble.
You make it sound like the 21% reduction for CV event in the 2020 Cochrane review is a small benefit compared to the ask, using the NNTT of 56 to prevent one event in 4 years.
However, most of the included studies have relatively young populations (at a glance, median of the average age must be ~55) which is way before CV events peak.
It's not exactly shocking you would need to treat many 55 yos to prevent CV events because they hardly get them in the first place, even when the inclusion criterias often use some risk factor.
On the flipside:
1/ if you've gone and swapped sat fats out for 4 years it's probably rather painless to keep the diet at vitam
2/ the standard model CVD risk is that LDL cholesterol is a cumulative risk. That is, the longer it's elevated the more risk you accrue. Suppressing it even if only for 4 years is due to have lifelong benefits even if diminishing over time
The 21% RR over 4 years figure is a scientific construct but I therefore don't think it makes much sense to use it in a practical discussion. It's more helpful to frame it as evidence that suppressing sat fats will lead to postponing CV events in those who would experience it.
Since CVD kills 1 in 3 people, I'll take it.
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this is a reasonable point! I will try to remember to bring it up if and when we ever get around to doing another Mea Culpa episode. thank you!
I'm surprised trans fats weren't addressed. The current concerns about seed oils feel directly connected to the past trans fat debacle. Public health officials advocated for trans fats as a replacement for saturated fats in the 70s and 80s, only for them to be proven highly detrimental. (Perhaps this warrants a separate discussion?) This history makes it difficult to trust public health messaging on seed oils. Furthermore, the fact that seed oils were hydrogenated to create trans fats, primarily to extend shelf life, complicates the effort to convince the public that seed oils are now safe.
https://www.theatlantic.com/health/archive/2013/11/when-trans-fats-were-healthy/281274/
>In the 1980s, some scientists began to associate heart disease with saturated fats, and in response, groups such as the Center for Science in the Public Interest and the National Heart Savers Association (NHSA) began to hound manufacturers for “poisoning America ... by using saturated fats,” and as a result “nearly all targeted firms responded by replacing saturated fats with trans fats,” as David Schleifer wrote in 2012 for the journal Technology and Culture.
I think it would be better if more people acknowledged that doing good nutrition science is complicated and difficult. That's why I like this show. Changing recommendations based on better evidence is a good thing, and it should make people feel more confident in our public health institutions, not less.
‘PUFAs’ just sounds like you’ve been in a coma since the 80s and can’t wait to start being homophobic again.
That was a key driver of my decision to go with Pee You Eff Ays rather than using it as an acronym
I can’t believe you weren’t aware that ‘piyu effay’ is an extremely offensive slur against bisexuals in much of Clackmannanshire. You’ve let the podcast down, you’ve let Stuart down, but most of all, you’ve let yourself down.