--snip--
While most experimental diet-induced obesity studies use high fat diets composed of lard or milk fat (rich in saturated fats), a few recent studies (including one from our group) have examined the effects of a diet rich in soybean oil and found that this vegetable oil does in fact increase adiposity, diabetes, insulin resistance and fatty liver9,13,14,15. Furthermore, soybean oil induces more metabolic effects than an isocaloric diet made from coconut oil13, which is nearly all saturated fats, albeit of shorter chain length than those in animal fat.
--snip--

Omega-6 and omega-3 oxylipins are implicated in soybean oil-induced obesity in mice

https://www.nature.com/articles/s41598-017-12624-9

No surprise here. I found that Omega 6 oils (most vegetable oils) definitely increased my inflammation issues.

I just read that Nina Teicholz is writing a second book on vegetable oils, a combo of politics and science gone wrong with health suffering, if I am understanding it correctly.

Jean

Question - how much soybean oil causes problems? I have it occasionally in store-bought mayonnaise, which I use sporadically, and in some of my sardines - but it's just the oil that sticks to the fish, I give the rest of the oil to the cats.

The rest of the time it's butter (rather a lot of it!), bacon grease, and coconut oil.

I'm assuming I eat too little of it to matter, and I'm wondering if any research has been done about how much is too much. I feel rather like a woman I knew who smoked 2 cigarettes a day. She had some people telling her it would give her cancer, others (like me) saying "enjoy."

Thanks for the heads up, Jean. I'm looking forward to this one. It's a story that needs to be told, and Nina will be relentlessly thorough!

Mouse studies with 1 percent linoleic acid vs. 8 percent show protection vs. weight gain, the difference between the supposedly fattening effects of a high fat diet for mice disappears when you correct for this. This looks on the order of the linoleic acid difference shown in this study in the coconut oil vs. coconut oil plus soy oil groups. A little fish oil also protects.

I remember Stephan Guyunet used to put the upper level for linoleic acid on a paleo type diet at about 4 percent, though I don't know whether he based this on controlled studies or more traditional levels of intake.

The fattening effect has sort of been traced down to endocannabinoid production, the linoleic acid is made into arachiconic acid which is used to produce endocannabinoids. The proof is that blocking endocannabinoids will reverse the fattening effects--but maybe not that surprisingly, in humans, endocannabinoid blockers are problematic in that they cause depression. And one symptom of depression is a decrease in appetite. So you gotta be a bit careful with this stuff. Omega 6 fatty acids aren't like cigarettes, just essential fatty acids that it might be possible to have too much of. Even that's uncertain. The !Kung people, I believe they're the folk in the Gods Must Be Crazy, traditionally eat as much as 60 percent of their diet from a nut that's a rich source of linoleic acid. Acorns are another rich source, even when our ancestors didn't eat them, their food did.

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

I'm not saying, this paleo group eats/ate it, so it must be safe for everybody, just pointing out that the evidence vs. omega 6 isn't perfect. I think it's prudent to keep it lowish but not absent--but sometimes things get a bit inflated, overestimate the importance of one factor, and there's a danger that some other more significant factor might seem less important by contrast.

Could a candidate for a factor be that the process of industrial extraction of seed oils for public consumption so distorts the ratio or that something else introduced in the extraction process puts these fats into the danger zone?

I understand we are supposed to ingest Omega 6 & Omega 3 in a one-to-one ratio. The Food Pyramid's insistence on low fat and that from vegetable oils that are high in Omega 6 is what is damaging, as I understand it.

Trans fats are a major possible factor. Fred Kummerow originally blew the whistle because they block the enzymes needed to process linoleic acid and linolenic acid into essential fatty acids, this can cause an essential fatty acid deficiency, fatty liver is one consequence, maybe a candidate for development of type II, in the long term. There are old studies making coconut oil look bad, it was hydrogenated, so whatever other effects of trans fats there might be, these were also essential fatty acid deficiency studies.

I think the omega 3/6 ratio unquestionably matters if you're not getting in sufficient EPA and DHA from the diet, and need to make some, but that there's room for debate about whether or not it matters if you are.

Even damaged fats--there are studies showing oxidized oils can actually be protective vs. fatty liver. Some sort of hormetic effect, with exposure to damaged oils increasing overall defenses? Of course that presents another rabbit hole, with the possibility that essential fatty acids protect vs. fatty liver, to some degree, because they're easily oxidized.

Speaking of damaged fats, highly processed damaged/oxidized industrially produced cooking oils are likely a whole different animal from non-rancid omega 6 oils in fresh nuts/seeds.

In just rereading Dr. Fung's "The Obesity Code" he does say the Omega6/Omega3 ratio should ideally be about 1:1, but in the modern western diet it's more like 15:1 to 30:1 - numbers I had read elsewhere.

I avoid the seed oils at home but do occasionally eat out and it's basically impossible to avoid them there. I do try to get helpings of fish. I'm especially fond of sardines

David Gillespie has also done a lot of research into vegetable oils and has some interesting posts:
http://davidgillespie.org/category/vegetable-oils/

I think he also wrote a book on the subject. Ahh, here it is:
http://davidgillespie.org/portfolio/toxic-oil/

I don't agree with everything the man says, but he has done a lot of research and come up with some very interesting data and talking points.

My body definitely reacts differently to foods cooked in vegetable oils vs foods cooked in butter/lard/bacon fat/coconut oil/etc. This is one of the many reasons I almost never eat out because pretty much no-one cooks in the good oils anymore. :/