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Comment by teslabox | Hacker News Reader

IMHO, the contamination of the food supply with rancid vegetable oil is a more important factor in the diabetes epidemic. Almost all of the vegetable oils at grocery stores are refined so customers don't realize they're using rancid oils. Vegetable oil is useful as biodiesel, and for making paints and stains.

  A drying oil is an oil that hardens to a tough, solid film 
  after a period of exposure to air. The oil hardens through 
  a chemical reaction in which the components crosslink (and 
  hence, polymerize) by the action of oxygen (not through 
  the evaporation of water or other solvents). Drying oils 
  are a key component of oil paint and some varnishes. Some 
  commonly used drying oils include linseed oil, tung oil, 
  poppy seed oil, perilla oil, and walnut oil. Their use has 
  declined over the past several decades, as they have been 
  replaced by alkyd resins and other binders.

- https://en.wikipedia.org/wiki/Drying_oil

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Refined oils have nothing to do with being rancid it’s an extraction technique that uses heat instead of pressing.

Refined oil will go rancid in the kitchen just as easily as cold pressed and you will noticed since it will smell sweet and then putrid.

Common cooking oils including canola do not oxidize well nor do they dry well which is why you would not use them on say wood because they will not dry and will just go rancid.

> Refined oils have nothing to do with being rancid it’s an extraction technique that uses heat instead of pressing.

The petroleum distillate hexane is used to extract the oil from seed meal, then is boiled off: https://en.wikipedia.org/wiki/Vegetable_oil#Solvent_extracti...

The specific step I'm referring to is "steam deodorization": https://en.wikipedia.org/wiki/Vegetable_oil#Deodorization

And this has nothing to do with the oil being rancid deodorization is used to remove any water soluble solvents that may have been used in the process of extracting the oil.

If you are going to link to Wikipedia at least bother reading the damn article.

If you want to talk about the potential health impact of oils then erucic acid consumption might be a topic for discussion despite the lack of conclusive research on the subject so excessive canola oil consumption might be an issue despite it being capped at 2% in the US and 5% in the EU if you consume enough of it you might cause cardio vascular damage if the existing correlated data also indicates causation.

But vegetable oils in general are not bad and are not sold as rancid that’s wrong, if you want to be on the extreme edge of the safe line then you can substitute canola oil with coconut, sunflower or peanut oil quite easily and these days also without paying a premium.

What does the blocktext and link have to do with your supposition?

Most so-called "vegetable oils" were traditionally used as drying oils. This was before the paint industry figured out how to use petroleum distillates in their products in the mid-20th century.

Linseed oil was renamed "flaxseed oil" when the market for stain made with linseed oil dried up.

Containers of vegetable oils typically develop a sticky film on them, due to the drying oil effect.

Maybe I'm not viewing this with the proper historical context, but I don't understand why you are saying the market for linseed oil has "dried up" for non-food uses. Boiled linseed oil, which contains linseed oil, is probably the most common oil based finish for woodworking.

I also looked at this website about "Linseed oil market analysis" [1], which shows that Paints & Varnishes is still the largest user of linseed oil. Then processed foods, then pharma, then cosmetic, then flooring (which is probably also as a finish).

I'm eye-balling the graphs because they don't have a table, but it looks like processed foods is only about 20% of the market. That might be a lot, I don't know, but it doesn't seem fair to say all this excess linseed oil is going into foods because there is no other use for it.

1: https://www.grandviewresearch.com/industry-analysis/linseed-...

... strictly speaking you’re certainly correct that there is still a significant non-food use for linseed and the other vegetable oils. But there were only limited food uses for polyunsaturated oils before deodorization and hydrogenation techniques were figured out in the early-mid 20th century. People might [have] measured out a tablespoon for their cooking pan, whereas today people use these oils prolifically.

This process sounds similar to seasoning a cast iron pan. Does that mean using a seasoned cast iron pan can play a factor in diabetes, since you're in taking more rancid fats?

Putting aside the fact that the claim made about rancid oil is pure fiction, the answer to your question is no. A cast iron pan is seasoned by carbonizing and polymerizing the oil under high heat, and what’s left can’t go rancid and isn’t really oil anymore.

It’s a very different process “seasoning” creates a thin carbon layer on the surface of them metal and essentially what it does is to fill all the small gaps that normally would allow food to get into and stick it’s essentially very simmilar to Teflon and other non-stick coatings.

That is exactly what pan seasoning is. It's why the oil you use matters. The patina on a seasoned pan is a crosslinked polymer.

The chemicals that make rancid oils taste and smell bad are generally the smaller bits that come off the molecule when its double bonds are attacked by oxygen: the aldehydes and ketones, and the short saturated fatty acids like butyric acid.

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