Department of things you'd know if you paid attention in high school chem

[nyuanshin]

. . . and little things that make me sigh: people who will acknowledge that frying with vegetable oil is unhealthy and yet think that polyunsaturated fats are good for you in low-temperature cooking. Increasing ambient temperature is just one way to facilitate (lipid) oxidation; lowering ambient pH is another. What do you think is happening when

Comments

[airstrip]

Organic chemistry isn't generally a topic of high school chemistry and what the dominant process is when heating a mix of compounds isn't the same for every mixture at every temperature. I'd be surprised if someone knew that without having looked it up.

[nyuanshin]

True: I recall oxidation reactions and pH being covered in high school, but the connection between the two wasn't made apparent until org chem in uni. So yes, I'm being very mean today. But if you grok the principles you should at least be able to guess, looking it up only to verify.

[airstrip]

I think most people would guess that cooking with oil, like steaming, is a way of transferring heat from a heating element to the food in a relatively even way. People who acknowledge that frying is bad probably have an "oil spill" model of it: the oil itself is unhealthy out of the can and frying means that, inevitably, this stuff is in your food because the food was dipped in it for a longish while.

[csn]

Most everyone I know doesn't pay any attention to what kind of oil they use, even the scientists. Funny, since it's probably at least as important as what foods you're eating, huh?

But what about fish? Those also have lots of polyunsaturated fats, right? Do you think they're unhealthy?

[nyuanshin]

I actually suspect so now. The evidence on health effects of dietary PUFAs is . . . weaker than is commonly advertised, to put it politely. It fits the same pattern I've seen before with SSRIs, statins, etc. -- initial studies say they're awesome, then as the years go on the failures to replicate using more rigorous methods by disinterested bodies start to pile up, etc. Same deal with antioxidants. I'll leave it as an exercise to speculate what incentive structures might be shaping this pattern.

[nyuanshin]

http://raypeat.com/articles/articles/fishoil.shtml

Disclaimer: this man is a crank. But when he sticks close to the facts he's mostly on-point, and the only reason I link to the article is that it pulls together some info you don't usually see. The tl;dr is that most of the PUFA are oxidized by the time they hit the blood stream, they get incorporated into membranes and reduce mitochondrial function, and the antinflammatory effects are a knock-on result of the damage it does to your immune system. Oops.

The joke is that the reason O-3's are used in your cell membranes is that they act as canaries in the coal mine: they're first to be oxidized under stress, which acts as a warning signal for the cell to prepare for further damage.

[kaimialana]

Here's a criticism: If you studied biochemistry, you also know that lipids, both polyunsaturated, monounsaturated and saturated, are absolutely necessary (and in specific amounts) for the continued fluidity and structure of cell membranes, and in basic neural insulation. The point isn't that lipids are or are not good for you, the point is that a person receiving either less than needed or a great excess is going to have health problems. The latter being the more prevalent condition.

[nyuanshin]

Everything you said is arguably correct -- except that last sentence, which is almost certainly false in this case.

[ferrouswheel]

So care to enlighten us as to why lipid oxidation a good thing for health?

[nyuanshin]

It isn't!

[nyuanshin]

That is, because oxidized lipids are useless junk molecules that can impair membrane function. Generally your innate immune system gets all hot and bothered by them, leading to inflammation and atheromas.

[keenman]

Why do people use oil to cook anyway? Just for the taste? I'm not much of a cook, but I've never needed it for what I make: stir fries, eggs, and the like.

[keenman]

Thanks for the info. I'll keep that in mind. :)