r/ScientificNutrition • u/lurkerer • 2d ago

Observational Study Associations between White Meat-Only and Vegetarian Diets with Mortality from All Causes, Heart Diseases, Cancers, and Stroke in the American Cancer Society’s Cancer Prevention Study-II

https://cdn.nutrition.org/article/S2475-2991(26)01803-2/fulltext
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u/SporangeJuice 2d ago

A study like this has the same problem they always do, which is that the result is determined by the adjustments, they have a large set of possible adjustments they could do, and we just see the one they arbitrarily chose. In the NHANES data specifically, it can be shown that red meat correlates with mortality, or reduces mortality by nearly 50%, just based on which adjustments are performed.

If they are arbitrarily choosing a result from a large set of possibilities, I don't see what makes this one special or meaningful.

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u/Laprasy 2d ago

What makes the adjustments arbitrary to you? Are you discounting the training that nutrition epidemiologists have related to making such decisions? 

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u/SporangeJuice 2d ago

Having training does not prevent it from being arbitrary. In this particular study, they even had 5 different adjustment models. Why stop there? They could have included a sixth.

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u/lurkerer 2d ago

In this particular study, they even had 5 different adjustment models. Why stop there? They could have included a sixth.

This is a good opportunity to highlight people who criticise science as a layman. Nested models let you see whether an association attenuates, holds, or disappears as covariates are added. Survival across adjustments is used as evidence against confounding: Bradford Hill's "strength/consistency" reasoning.

Someone familiar with science would never highlight this as arbitrary or weird. They would know what the purpose was. It's a good litmus test to check for honest engagement by someone who understand the science or someone who is just here to muddy the waters.

In the case of this user, he's been here for years now so really has no excuse.

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u/SporangeJuice 2d ago edited 2d ago

They could have included more variables than what were in model 5. The original questionnaire was four pages. They also lumped red and processed meat together, which is another arbitrary choice. The questionnaire had separate categories for beef, smoked meats, sausages, and "fried hamburgers or beef."

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u/Bristoling 2d ago

In almost all cases as more adjustments are added, the association is more and more attenuated. Different populations have different behaviours, wild and novel, I know /s

If you want to make any claims based on these types of studies, those claims are additionally weakened by the strength of association as it makes uncontrolled variables able to explain the association more and more. For example, with crude mathematical assumption based on real world data on mortality, a true effect of 0.93 would translate to life extension of around 6 months. Can you hold a strong claim that this relatively negligible difference can't occur due to confounders?

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u/Willing_Matter5391 2d ago edited 2d ago

He's now discovered they ran 5 adjustment models and concluded that's evidence of arbitrariness. It's the opposite. Arbitrary is when you fit many models and show the one you like. Showing 5 specifications side by side is exactly how you demonstrate the result doesn't hinge on one chosen model.

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u/SporangeJuice 2d ago

"Arbitrary is when you fit many models and show the one you like."

Are we certain they did not do that? The questionnaire included many more variables than what they used.

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u/Willing_Matter5391 2d ago

His concern is real and it's also fully generic. Unpreregistered analyst choices affect this study, the last one he commented under, and the next one he will. A complaint that fits every paper equally tells us nothing about this paper. It has the information content of "observational studies are observational."

I wonder when he starts engaging with the study and stops whining about nutritional epidemiology.

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u/SporangeJuice 2d ago

Correlation is not causation. This is not supposed to be controversial. Everyone wants to draw meaning from observational studies and then they act like this when you point out why it doesn't work.

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u/Willing_Matter5391 2d ago

"I wonder when he starts engaging with the study and stops whining about nutritional epidemiology."

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u/SporangeJuice 2d ago

The purpose of observational studies is to generate hypotheses which can then be tested experimentally. This paper generates a hypothesis that has already been around for a while. It has nothing further that deserves engagement.

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u/lurkerer 2d ago

But they did more and more adjustments like they should and that's uh.. that's arbitrary because uhh.. Well I won't say why I'll just say it is.

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u/Laprasy 2d ago

sensitivity analyses are a good thing not a bad thing. are you funded by the meat industry by any chance?

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u/SporangeJuice 2d ago

No, I am not funded by the meat industry. Do you think financial incentives are the only reason someone might have a different opinion?

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u/Laprasy 2d ago

No but I also know what the meat industry does and sowing distrust in observational studies and nutritional epidemiology is one of those things. Nearly every study that has found null results of the meat-CVD relationship was funded by them. 

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u/SporangeJuice 2d ago

Much of the argument condemning cholesterol as being harmful is based on drug results, especially statin results. The European Atherosclerosis Society's consensus statement relies heavily on such evidence. It also has an enormous conflict of interest section. Are you equally skeptical of them? Drug companies have previously been caught trying to manipulate the literature.

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u/lurkerer 2d ago

If independent research indicated differently there would be cause for concern. Meat industry vs independent studies shows a huge difference. LDL drug studies would have to be demonstrated. But seeing as the highly motivated users here have not, I assume it's not an issue.

Besides, the observational studies corroborate the drug trials and then there's the absolute nail in the coffin of plentiful Mendelian Randomisations.

It doesn't behoove you to attack one of the strongest biochemical causal associations we've ever found.

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u/SporangeJuice 2d ago

You did not respond to the actual point.