I was having a conversation with a friend about this old article: Seed Oils and Body Fatness: A Problematic Revisit
These are my thoughts:
So he (Guyenet) has like 7 papers for his nice linear graph. All of them use different populations. Some of them are women only, some are men only, some are both. But he lumps them together and plots them over time. Ok, the problem with this is that, first men’s requirements for LA are more than women by quite a bit so you can’t just lump this all together and plot this over time that is a big FAIL.
The second thing is that deposited LA in fat stores tells you nothing about utilization or consumption habits. This has been demonstrated as early as 1936. In fat free diets when you add small amounts of LA something like 1-2% there is a marked increase in deposited LA, as in, almost all of it gets deposited in fat depot tissue because it shuts down de novo lipogenesis. This seems to be a direct function of LA by decreasing expression of SREBP-1c, which is major regulator of DNL, which is interesting because if you aren’t eating LA and eating a fat free diet in some people this causes RAPID weight gain, fat that is laid down is more oleate instead of palmitate which probably makes it increasingly hard over time to go without food.
But when you add medium chain and long chain fatty acids to the diet and you feed LA, LA is dramatically reduced in adipose tissue as LA utilization (metabolically as opposed to bio-synthetically) is a function of the chain length of the fatty acid. For example, in rats fed fat free diets, diets with MCTs, and diets with LCTs, fat depot LA levels are respectively 21%, 11%, and 6%.
So, EVEN if there is more LA in adipose tissue, it doesn’t tell you anything about actual CONSUMPTION, all it tells you loosely is the composition of fats and carbohydrates in a person’s diet, it does not tell you about CONSUMPTION habits AT ALL because you can take someone on a low fat diet who eats low amounts of LA and it all will be deposited into depot fat, but you can take a person who is on a moderate or higher fat diet eating the same amount of LA as the person on the low fat diet and they will have LESS LA in their depot fat.
That’s literally the only conclusion you can draw, so you can not copy and paste historical soybean oil availability charts and paste them on top of depot fat composition on mixed groups of people over time and then say boom we are eating more LA because of soybean oil and look there is also more in our fat, doesn’t work that way.
P.S. Next post will be why you don’t want your mitochondria to be depleted of LA. It’s not good.