Altered EFA due COOKING good - altered EFA due to RANCIDITY bad - why ? page

[danandvicky]

Hi Everyone,
A simple sounding question that has been giving me trouble for a while. Hopefully someone on here can explain it to me.

I understand that Polyunsaturated Essential Fatty Acids are less stable than Monounsaturates, which are less stable than Saturated fat - which in turn increases the risk of the oils going rancid as oxygen infiltrates the carbon bonds that are not saturated with hydrogen atoms. We all know rancidity is bad.

I dont understand the process that occurs due to cooking regarding polyunsaturated oils. I would assume the heat alters the oil in some way ? -if so, is this alteration beneficial or harmful to human health ? I would assume the very fragile nature of polyunsaturates would mean that they have a very low 'smoke point' - after all, there has been much discussion on cooking with olive oil (much more stable than fish oil) on this site.

Basically, how can cooking fish not alter the fish oils inside, the same way oxygen does when it makes the oils go rancid ?

Many thanks in advance for anyone that can solve this one for me - i hope there's a post somewhere i can be linked to .

[Paysan]

Sorry, can't help you on cooking, but when oxygen binds with PUFA's, the result is rancidity. Bet you knew that! But rancid fats destroy other vital nutrients in the body, like Vit E. The only reason I became aware of this was when a frugal goatkeeping friend used up the last of her Vit A-D-E food supplement for her pregnant goats. She figured she was saving money by not throwing away rancid oil. But at 3 weeks of age, her little goat kids bouncing around their pen would suddenly drop dead. Autopsies revealed heart attacks, and the prime culprit was the rancid oil.

Unless the putative fish that you are cooking is totally exposed to air while being cooked, I sincerely doubt if the fish oils can go rancid, surrounded as they are by tissue. I've heard that's why you shouldn't scramble eggs, (Mercola) but, who knows?

[danandvicky]

Thanks for the reply.

I guess there would be some 'denaturing' going on then? in the tissues exposed to the most air ?

Its a strange one - i hope someone has some definitive info.

[Paysan]

Thanks for the reply.

I guess there would be some 'denaturing' going on then? in the tissues exposed to the most air ?

Its a strange one - i hope someone has some definitive info.

Well, in my internet forays, I came across some more info on rancid fats by Bruce Fife:

Rancid Oils

Still looking for actions of cooking. HTH

[Paysan]

And this is what I came up with, from the Blog of Dr Eades:

I got an article in my inbox today about the risk of oxidized fats in fish oil capsules, even those that are well within the expiration date on the bottle.

"We wrote about this very thing in the Protein Power LifePlan back in 2000.

Fish oil is primarily EPA and DHA, both of which are extremely unsaturated. And, as we all know, the greater the degree of unsaturation, the greater the propensity to go rancid. When these oils go rancid (or “go off” as the Brits put it) they don’t go from being healthful to simply becoming neutral, they actually convert to harmful oxidized fats called lipid peroxides."Endquote

From what I can determine, eat your fish fresh, cook it gently and consume at once. Fish oils are not as stable as saturated fats, and fish rot easily, which means they're rancid. Cooking and eating correctly means you are consuming the fish before it gets a chance to harm you. Many fish oil supplements on market are rancid, despite the expiration date.

[danandvicky]

Hi Paysan,
many thanks for the replies and for the extra research.

The stuff from Dr Eades appears to be a restatement of part of my question and your musings dont really answer it either. Im trying to find out how to, or if it is even possible to, cook and eat fish 'correctly' due to the inherent nature of polyunsaturated fats. I wonder how long is it before oily fish become harmful ? 2-3 days perhaps for the oils to start to oxidise ? and when cooked, at what temperature does the heat start to have a harmful effect on the oils ?

I havent seen anything on these forums or anywhere else for that matter that can explain my original question.

If polyunsaturates are so delicate and go rancid at the drop of a hat, surely cooking must be harmful when it comes to oily fish ?

[BlissfulWriter]

Saturated fat is more stable than monounsaturated fat, which is more stable than polyunsaturated fats. It all has to do with the number of double bonds they contain. The double bonds have missing hydrogen atoms and hence are chemically unstable and hence easily broken by heat. Saturated fat has no double-bond. Monunsaturated has one. Polyunsaturated has multiple double bonds.

Processed polyunsaturated oils in bottles are not healthy and should not be used for cooking as they are so easily damaged (oxidized) by heat. The polyunsaturated oils in the store shelf are probably already damaged due to the heat in processing the oil. I use saturated oil (such as coconut) oil for cooking.

The polyunsaturated oil (DHA and EPA) from fish is fine and I try to eat lots of fish. Sure, the cooking of the fish may damage a little bit of it. But the benefits outweighs. If you lightly steam the fish, it is best. Deep fried is a big no-no.

[peril]

Sashimi

[danandvicky]

"Saturated fat is more stable than monounsaturated fat, which is more stable than polyunsaturated fats. It all has to do with the number of double bonds they contain. The double bonds have missing hydrogen atoms and hence are chemically unstable and hence easily broken by heat. Saturated fat has no double-bond. Monunsaturated has one. Polyunsaturated has multiple double bonds."

My initial post includes the chemistry - im aware of these facts. Also, i am not suggesting we should use fish oil to cook with - im asking if there is damage to the PUFA's in oily fish if it is cooked. I love some grilled(broiled) mackerel, herring or sardines but if its as harmful as guzzling a glass of rancid cod liver oil, then i would like to know about it.

Im assuming that it isnt harmful to cook oily fish otherwise there should be some science somewhere but i havent heard any argument or even questions either way. This is the thing that baffles me.

[Paysan]

"Saturated fat is more stable than monounsaturated fat, which is more stable than polyunsaturated fats. It all has to do with the number of double bonds they contain. The double bonds have missing hydrogen atoms and hence are chemically unstable and hence easily broken by heat. Saturated fat has no double-bond. Monunsaturated has one. Polyunsaturated has multiple double bonds."

My initial post includes the chemistry - im aware of these facts. Also, i am not suggesting we should use fish oil to cook with - im asking if there is damage to the PUFA's in oily fish if it is cooked. I love some grilled(broiled) mackerel, herring or sardines but if its as harmful as guzzling a glass of rancid cod liver oil, then i would like to know about it.

Im assuming that it isnt harmful to cook oily fish otherwise there should be some science somewhere but i havent heard any argument or even questions either way. This is the thing that baffles me.

Would the fact that generations of seafaring folk and coast dwellers didn't drop dead en masse add anything to the safety of fish oils in your mind?