It's the fat. Specifically, the shift from saturated to unsaturated fat over the last many decades.
4/ "This suggests that alterations in the intake of saturated relative to unsaturated fat over the past 100 years may have contributed to the decline in BEE reported here, although... further studies in humans are required."
5/ Pretty remarkable finding, from world-class researchers and a world-class database.
6/ There are a few things I disagree with in this paper, but I'll just quote from one of their refs, 36:
“...These studies suggest that the n-6/n-3 ratio per se is an important modulator for white-to-beige thermogenic conversion through oxygenated lipid mediators (oxylipins)..."
7/7. I can live with that. The needle doesn't get moved all the way in one paper. Read the whole thing. (Some nuance omitted here!) Thanks to
1/ "Human and animal studies support that consuming a high level of linoleic acid (LA, 18:2ω-6), an essential fatty acid and key component of the human diet, increases the risk of colon cancer."
#lcl6 @kevinfolta @talkingbiotech
2/ "Given the importance of LA in the human diet, it is crucial to better understand the molecular mechanisms underlying its potential colon cancer-promoting effects."
3/ "Administration of a diet rich in LA, at human consumption levels, exacerbates AOM/DSS-induced colon tumorigenesis in mice"
1/ "Paradoxically, the increases in body weight, particularly in Western countries, occurred during a period of emphasis on diets low in fat as a means for avoiding weight gain....
2/ "These dietary recommendations were based largely on the concept that high-fat diets were less satiating (39) and that reducing dietary fat reduced risk for cardiovascular disease by lowering circulating fat and cholesterol (5)....
"Perceived"? 🙄
3/ "As a result of the perceived failure of traditional dietary advice, attention shifted to alternative dietary regimes, including low-glycemic-index diets and very-low-carbohydrate ketogenic diets...."
1/ "The evidence for cardiovascular benefit in these drugs is very strong, and the prescribing labels for them are being updated to include reduction in stroke and other cardiovascular events."
2/ "Recently [2019], several GLP-1 receptor agonists have been found to have cardiovascular benefit independent of their glucose lowing ability. Liraglutide is one of clinically approved effective GLP-1 receptor agonists."
3/ "In this study, we explored the molecular mechanism of Liraglutide against oxidized low-density lipoprotein (ox-LDL) in cultured endothelial cells."
1/ Farmed salmon have become fat bags of canola oil.
"The average total lipid content of the farmed salmon muscle was found to be four times that of the wild salmon (8.97 ± 0.63% and 2.14 ± 0.32%, respectively)."
2/ They're full of linoleic acid:
"Furthermore, LA, ...[is] present in large quantities in both farmed salmon and the feed. OA, LA, and ALA are most commonly found in plant sources, and together with C16:0 they are the main constituents in rapeseed oil (Sharafi et al., 2015).
3/ Why?
"Rapeseed oil is one of the main ingredients in salmon feed in Norway today (Aas et al., 2019)."
1/ Why is it difficult for folks to determine the effects of seed oils?
Take this paper:
"4-HNE Immunohistochemistry and Image Analysis for Detection of Lipid Peroxidation in Human Liver Samples Using Vitamin E Treatment in NAFLD as a Proof of Concept"
#lcl6
2/ It's from @NIH .
Take the introduction:
"Lipid peroxidation is the process in which oxidants, such as free radicals, react with double bonds in the carbon chain of fatty acids, especially polyunsaturated fatty acids.... doi.org/10.1369/002215…
3/ "...In food production, lipid peroxidation products lead to distinctive flavors, for example, in dried cured meats such as Parma ham, but within the human body these can lead to cell injury through modification of macromolecules."