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LA speculation

Speculation on health effects of 18:2 ω-6 LA(Linoleic Acid)

LA is the most common PUFA. LA has been promoted due to an effect of lowering cholesterol numbers. This has not been shown effective to reduce other end-points such as all-cause-mortality. Recent research has shown that LA induces inappropriate insulin sensitivity. This effect I think is beyond speculation. It is important to note that this is not part of the LA => AA theory about the dangers of PUFAs. What follows are speculations that are due to other metabolic pathways.

Obesity and T2D pandemic

From 1960 on there has been a great increase in the consumption of LA. There is some significant correlations to consider. While correlations do not show causation - they do suggest the need for careful experiments to rule out the causation - these have not been done.

Possible Experiments

It is possible to get the LA content of adipose tissue via NMR. This level is an objective measure of LA exposure and correlations with obesity/T2D and other disease can be explored.

Consumption of ω-6 and seed oil over time

• From Stephan vegetable-oil-and-weight-gain

"The linoleic acid content of body fat has increased tremendously in the US over the last 50 years, as shown in the following graph, based on a number of different studies, each of which is represented by an orange dot

http://www.ncbi.nlm.nih.gov/pubmed/1130317
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1216266/
http://www.ncbi.nlm.nih.gov/pubmed/3728359
http://www.ncbi.nlm.nih.gov/pubmed/1858698
http://www.ncbi.nlm.nih.gov/pubmed/9440371
http://www.ncbi.nlm.nih.gov/pubmed/12559671
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2515528/

" I also included a study that looked at the linoleic acid content of chimpanzee fat, for reference

"The caveat is that the paper doesn't specify if the chimp was captive or wild, so you can take it with a grain of salt.
Linoleic acid in human breast milk has also increased quite a bit over the same time period

LA has an approximate 600-day half-life in adipose tissue by some accounts, thus changes in diets are not going to show sudden changes in weight in a way that people would see a cause connected to an effect - the same problem with research.

Low T3 effect? or blocking of T3?

There are some papers that show a blocking activity of lipogenic enzymes.

LA Thyroid connection?

• The influence of diet on the lipogenic response to thyroxine in rat liver.
• Inhibition of triiodothyronine's induction of rat liver lipogenic enzymes by dietary fat.
• Triiodothyronine-dietary interrelationships in the modulation of brown adipose tissue and liver lipogenesis in the rat.
• Effects of diet composition on serum levels of insulin, thyroxine, triiodothyronine, growth hormone, and corticosterone in rats.
• The influence of diet on the lipogenic response to thyroxine in rat liver

Increases oxLDL causing CAD

• 18:2 ω-6 linoleic acid -5°C increases LDL oxidation - One really does not want to eat much of this - varnish, linoleum, industrial waste.
  • A high linoleic acid diet increases oxidative stress in vivo and affects nitric oxide metabolism in humans
  • Linoleic Acid Increases Lectin-Like Oxidized LDL Receptor-1 (LOX-1) Expression in Human Aortic Endothelial Cells
  • Dietary linoleic acid elevates the endocannabinoids 2-AG and anandamide and promotes weight gain in mice fed a low fat diet.

Increases in oxLDL and other products of LA may cause degenerative diseases of cartilage and joints

• "Monounsaturated and Saturated, but Not n-6 Polyunsaturated Fatty Acids Decrease Cartilage Destruction under Inflammatory Conditions"

LA fed formation of HNE causing harm

• • The Lipid Peroxidation By-Product 4-Hydroxy-2-Nonenal (4-HNE) Induces Insulin Resistance in Skeletal Muscle through Both Carbonyl and Oxidative Stress
  • Measurement of HNE-protein adducts in human plasma and serum by ELISA—Comparison of two primary antibodies
  • Biomarkers of Oxidative Damage in Human Disease 4-HNE from LA
  • Cell death and diseases related to oxidative stress:4-hydroxynonenal (HNE) in the balance HNE again

More references

• • Measuring Blood Fatty Acids as a Surrogate Indicator for Coronary Heart Disease Risk in Population Studies

• • Dietary fats: a new look at old data challenges established wisdom Once hidden by Keys - how many dead?
  • Re-evaluation of the traditional diet-heart hypothesis: analysis of recovered data from Minnesota Coronary Experiment (1968-73) Where the BS started
  • Osteoarthritis and Omega-6 Fats (Linoleic Acid)

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