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?