TLDR - Linoleic acid is bad, has gone up by 140%, has a half life of 600 days, and gets stored in fat tissue, Dietary sources of LA (industrial oils) have a direct influence on body composition.

Linoleic acid (LA) is a bioactive fatty acid with diverse effects on human physiology and pathophysiology. LA is a major dietary fatty acid, and also one of the most abundant fatty acids in adipose tissue, where its concentration reflects dietary intake. Over the last half century in the United States, dietary LA intake has greatly increased as dietary fat sources have shifted toward polyunsaturated seed oils such as soybean oil. We have conducted a systematic literature review of studies reporting the concentration of LA in subcutaneous adipose tissue of US cohorts. Our results indicate that adipose tissue LA has increased by 136% over the last half century and that this increase is highly correlated with an increase in dietary LA intake over the same period of time.

Full Paper https://doi.org/10.3945/an.115.009944

  • jetOPMAEnglish
    2·
    4 days ago

    The introduction is worth quoting

    Linoleic acid (LA) (18:2n–6) is an 18-carbon n–6 PUFA with diverse effects on human physiology. LA is linked to skin barrier (1), immune (2), cardiovascular (3, 4), and neurobiological (5) functions, and, as a precursor of arachidonic acid and its metabolites, to reproductive (6), thermoregulatory, and digestive functions (7). In addition, LA is a natural ligand for PPARs (8). PPARs are intimately involved in the regulation of metabolic functions, including lipid and glucose metabolism, and they have been implicated in obesity and cardiometabolic disease risk (9). PPARα agonism may contribute to the ability of dietary LA to reduce circulating concentrations of total and LDL cholesterol (10). Finally, LA can influence biological processes via its nonenzymatic oxidation products. Oxidation of lipids in LDL is a risk marker for coronary heart disease (11). Because of its abundance in LDL and susceptibility to oxidation, LA is the most commonly oxidized species in LDL (12). The LA content of LDL reflects dietary intake (13).

    Many seed oils are rich in LA, and consumption in the United States has increased substantially over the last half century (14). Much of this increase has come from soybean oil, which contains between 50% and 60% of total FAs as LA (14). Adipose tissue concentration of LA is particularly responsive to dietary LA, as demonstrated by diet modification trials (10). As such, it is used as a biomarker of dietary intake (15). We hypothesized that increases in dietary LA in the US food system have led to increased adipose tissue concentrations of LA. To test this hypothesis, we conducted a systematic literature review of studies that have reported the LA concentration of subcutaneous adipose tissue. Our findings suggest that adipose tissue LA has more than doubled in the United States over the last half century and correlates strongly with LA in the US food supply, potentially influencing numerous aspects of human physiology and pathophysiology.

    Given the very long half life 680d of LA, it takes years to reduce the concentrations in adipose tissue. Dietary LA is directly associated with fatty LA deposits. The primary source of LA in the modern diet are industrial oils (seed oils, vegetable oils).

    A thank you to @xep@fedia.io for the Dark Calories book recommendation, I’ve made it to chapter 2 and am digging through the references as they pop up.

    • psud@aussie.zoneMEnglish
      2·
      2 days ago

      680 day half life, 10 half lives to practically eliminate LA from your body after you quit those oils. 6800 days – just over 18.6 years. I’m 2.6 years into this way of eating, probably 10 into restricting most oils other than olive, so somewhere between 8 and 16 years from now I should be good.

      Last time I had an industrial oil was last time I had tinned fish, while I was doing keto, years and years ago.

      • jetOPMAEnglish
        2·
        1 day ago

        You are what you eat. It’s insidious. It makes sense that fat is stored energy so if we build it with bad things when we unpack it will still be bad.

        Kinda like the LSD users who get random trips throughout their lives from stores LSD in their fat.

        I suppose you could speed up the LA usage by doing fasting and refeeding with clean food.

        • psud@aussie.zoneMEnglish
          2·
          1 day ago

          Possibly. I wonder if the quoted half life considers fat burning diets. If you can burn it, perhaps it’s time for a protein restricted crash diet

          • jetOPMAEnglish
            2·
            1 day ago

            I don’t think a crash diet is warranted as a intervention. Regardless of when you burn it (now vs later) its going to cause inflammation and reduced ATP production. I think its better to let it happen very slowly, naturally, so that your bodies inflammation budget is high and it isn’t a big deal. Forcing it all at once doesn’t seem like a great idea. Just keep eating clean and healthy!

    • jetOPMAEnglish
      2·
      4 days ago

      TLDR for the TLDR - Industrial Oils are bad, don’t eat them.

      This is relevant to carnivore because industrial oils are made from plant seeds, and carnivores avoid plant products. Even people following a strict ketogenic diet still get plenty of industrial oils in their food. Even whole food, single ingredient, diets still recommend industrial oils. It’s everywhere.