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Esterification - PUFA vs SFA

I'm guessing that many readers of this forum aren't huge fans of PUFA, so I thought this study would be of particular interest https://www.researchgate.net/profile/Asuka-Tani/publication/265479720_Metabolism_of_retinyl_esters_in_humans_after_ingestion_of_retinol/links/56bb31e108aebb3054a86d18/Metabolism-of-retinyl-esters-in-humans-after-ingestion-of-retinol.pdf

The experiment starts by feeding the volunteers this delicacy:

37 g of rapeseed oil and a few drops of retinyl palmitate (Chocola A, Eisai Co., Ltd. Tokyo, Japan) equivalent to 32.7 mg of retinol (0.114 mmol)

Then sets out to measure the amounts of the various retinyl esters in the serum after this delicious meal. I'll immediately reveal the punch line:

Re-esterification ratios (molar ratios between the concentrations of fatty acids and the corre- sponding retinyl esters recovered in serum after the ingestion of rapeseed oil and a retinyl palmitate) were markedly increased in saturated fatty acids (palmitic and stearic acids). Re-esterification ratios of unsaturated fatty acids (oleic and linoleic acids) were low compared with saturated fatty acids.

How big is the difference? Stearic and Palmitic acids are up to 7x more effective than Oleic at the peak. Oleic is about 3-4x greater than linoleic. The paper has nice graphs, do check them out. 

It's particularly interesting that Oleic (not a PUFA) is quite inferior to saturated fats. The lard vs butter distinction Grant pointed out immediately comes to mind.

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Quote from Rudi on September 20, 2021, 11:25 pm

I'm guessing that many readers of this forum aren't huge fans of PUFA, so I thought this study would be of particular interest https://www.researchgate.net/profile/Asuka-Tani/publication/265479720_Metabolism_of_retinyl_esters_in_humans_after_ingestion_of_retinol/links/56bb31e108aebb3054a86d18/Metabolism-of-retinyl-esters-in-humans-after-ingestion-of-retinol.pdf

The experiment starts by feeding the volunteers this delicacy:

37 g of rapeseed oil and a few drops of retinyl palmitate (Chocola A, Eisai Co., Ltd. Tokyo, Japan) equivalent to 32.7 mg of retinol (0.114 mmol)

Then sets out to measure the amounts of the various retinyl esters in the serum after this delicious meal. I'll immediately reveal the punch line:

Re-esterification ratios (molar ratios between the concentrations of fatty acids and the corre- sponding retinyl esters recovered in serum after the ingestion of rapeseed oil and a retinyl palmitate) were markedly increased in saturated fatty acids (palmitic and stearic acids). Re-esterification ratios of unsaturated fatty acids (oleic and linoleic acids) were low compared with saturated fatty acids.

How big is the difference? Stearic and Palmitic acids are up to 7x more effective than Oleic at the peak. Oleic is about 3-4x greater than linoleic. The paper has nice graphs, do check them out. 

It's particularly interesting that Oleic (not a PUFA) is quite inferior to saturated fats. The lard vs butter distinction Grant pointed out immediately comes to mind.

If I understand the premise, correct me if I'm wrong, is that re-esterfication is preferred due to stability and proper storage and therefore linoleic acid should really be avoided as much as possible? And Oleic acid to a slightly lesser degree but still significant compared to Stearic and Palmitic acids?

From the same study:

The dominant ester here was retinyl stearate followed by retinyl palmitate and retinyl oleate in ferrets, dogs and silver foxes, while, in the serum of raccoon dogs and humans, retinyl palmitate dominated over retinyl stearate

So it seems to be at least species dependant.

is that re-esterfication is preferred due to stability and proper storage and therefore linoleic acid should really be avoided as much as possible

That would be my line of speculation as well.

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