I was listening to the ABC's "What's That Rash?" podcast on seed oils today. Dr Norman Swan said that the studies he saw showed that mono and polyunsaturated fats don't increase CVD risk, inflammation etc. But keep in mind these studies are generally done on general western populations that have a high fat (including high saturated fat) diets. So any substitution is generally going to be benificial. I've already shown in previous posts that those on a low fat plant only diet generally won't benefit from adding oils to their diet. So it's a matter of context.
One aspect that did interest me, which has been debated in the past, is the value of the omega 6:3 ratio. Norman was saying that the division of one beneficial fatty acid by another beneficial fatty acid doesn't make sense. I take his point as I gave up taking note of the ratio probably more than a year ago. Once study said:
British Journal of Nutrition wrote:One topic of debate within the fatty acid field is the clinical relevance of the dietary ratio of n-6 to n-3 fatty acids. At one point, the consensus was that a high ratio was considered to be harmful because LA and ALA compete for desaturation enzymes, and because metabolites of n-6 AA were considered to be pro-inflammatory. However, the utility of this ratio has been rejected by health agencies throughout the world. One reason for this rejection is the recognition that the in vivo conversion of LA to AA is negligible, and another reason is that some metabolites of AA exert anti-inflammatory effects. There is also concern that, because of its multiple double bonds, LA intake could promote oxidative stress. However, clinical trial evidence shows the intake of n-6 PUFA does not increase markers of inflammation or oxidative stress.
[My bold]
https://www.cambridge.org/core/journals ... DD8E6DC3F3
Please keep in mind that the acknowledgements section of this study has a long list of national and international groups representing the growers of the sources of the plant oils that funded the study.
This Cochrane review of 19 studies on preventing CVD with omega-6 fats came to the conclusion that omega-6 fats had little to no benefit in preventing CVD. Which I suppose supports the podcast's point that they don't give evidence of doing any harm either. Cochrane is considered to be one of the most trustworthy sources.
There are 3 other studies cited by the podcast:
https://pubmed.ncbi.nlm.nih.gov/30971107/
https://pubmed.ncbi.nlm.nih.gov/29566193/
https://iris.who.int/bitstream/handle/1 ... sAllowed=y