Raw data from a 40-year-old study raises new questions about fats (2017) | Hacker News Reader

Raw data from a 40-year-old study raises new questions about fats (2017)

scientificamerican.com

25 pointsemmelaich7 comments

Note that this is mostly about saturated fat sources versus polyunsaturated fats. These polyunsaturated fats were all high in omega 6, which is widely regarded as less heart healthy than omega 3 oils or monounsaturated fats such as olive oil, avocado oil, or high oleic sunflower oil. Equivocating the results here as plant fats versus animal fats misses most of the nuance.

In a sense, though, I think this is exactly the point of the article: when this study was run, we didn't know about omega-N fatty acid profiles of fats. So things that seemed "obvious" didn't pan out in RCTs like this one.

Today, most of the RCTs about things like omega-3 fatty acids show no effect. Why?

My guess at the root cause is a bit of scientific reductionism mixed with overgeneralization. Omega-3 fatty acids are a great example, and often it looks like this:

1. Shockingly healthy population X has a diet rich in foods A, B, and C. What do A, B, and C have in common? Perhaps it's some micronutrient in abundance (like omega-3 in high-fat fish-eating cultures). Logically, the cause might be that micronutrient!

2. Early observational studies that happen to pass publication thresholds show promising connections. People who eat salmon -- high in Omega-3 -- are healthier! They have lower triglycerides, or cholesterol, or whatever.

3. RCTs show no positive effect from supplementing omega-3 fatty acids.

What happens between 2 and 3? Observational studies can't really isolate the effect of a single micronutrient, because there are a ton of interactions happening. Probably one of those other interactions is also necessary, but we don't know what it is -- much like how "plant fats" vs "animal fats" misses a ton of nuance.

I'm not really sure what we can do about this, though, except stop getting excited in phase 2?

Supplementing is not the same as avoiding. As you say, the interactions are complex. Maybe it isn't that supplements of omega3 are beneficial, since omega3 and omega6 compete, but avoiding omega6 while having sufficient omega3 gives the benefit. Any RCT support the negative properties of omega6?

I just read the whole thing quickly and while I cannot vouch for the data and reporting, the article seems to go wider than just that, including raising doubts against the cholesterol theories.

See the recent "FAT: A Documentary" (Amazon Prime has it) or the book "The Big Fat Surprise" by Nina Teicholz for many more details. I found these entertaining and compelling.

> The Frantz children always felt fortunate that their father brought his work home, his beliefs about the dangers of saturated fat shaping what the family ate. “Other kids would have ice cream; we had ice milk,” recalled Ivan Frantz. Bob said they were “reared on margarine,” foreswearing butter’s saturated fat.

I think this is key. This debate isn't about corporate shills, but honest disagreement between sincere, hard working scientists. It shows how hard nutrition science in particular can be.

So the population was mental hospitals and nursing homes?

They certainly isolated away exercise as a variable.

Likely cause is the good old bias against publishing null or negative results.

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