5 replies to this topic

[InquilineKea]

E,g, are longer saturated fatty acids better than shorter ones?

What about longer mono/poly-unsaturated fatty acids?

[niner]

It may actually be the other way around- shorter SAFAs better than longer ones. Some examples here are butyric acid- 4 carbons; coconut oil- in the range of 6-9 carbons (-ish). I don't know exactly how it would relate to unsaturated acids.

[InquilineKea]

Hmm - really? Stearic acid is definitely one of the healthier saturated fats, but it is 18 carbons long.

I wonder if the relationship isn't monotonic though.

Edited by InquilineKea, 30 May 2013 - 03:55 PM.

[niner]

How were the health rankings developed? It might be dose dependent.

[InquilineKea]

Stearic acid not being too bad: http://en.wikipedia....acid#Metabolism

Palmitic acid being bad: http://en.wikipedia....#Health_effects

[niner]

Wow, it's surprising how different the effect is, considering the similarity of their structures. I wouldn't have guessed that, but I suppose that just goes to show how subtle and unpredictable biology can be. Palmitic (16:0) is about twice as prevalent in butter and lard than stearic (18:0). The short chain SAFAs from MCT oils are yet another thing, since they don't follow the same digestive process as the long chain SAFAs do.

Here's the abstract and author's summary from the paper cited in Wikipedia.

Am J Clin Nutr. 1994 Dec;60(6 Suppl):1023S-1028S.
Metabolism of dietary stearic acid relative to other fatty acids in human subjects.
Emken EA.

USDA, ARS, NCAUR, Peoria, IL 61604.

This paper reviews results obtained by stable-isotope-tracer methods for stearic acid (18:0) and palmitic acid (16:0) metabolism and the influence of dietary linoleic acid on the metabolism of these saturated fatty acids in humans subjects. The results, based on stable-isotope-tracer data, show that absorption of 18:0 is not significantly different from 16:0; percent desaturation of 18:0 to 9-cis 18:1 (9.2%) is 2.4 times higher than for 16:0 to 9-cis 16:1 (3.9%) and 9-desaturation is not greatly influenced by the amount of linoleic acid in typical US diets. Additionally, compared with 16:0, 18:0 incorporation is 30-40% lower for plasma triglyceride and cholesterol ester and approximately 40% higher for phosphatidylcholine; beta-oxidation of saturated fatty acids was slower than for unsaturated fatty acids and increasing the intake of dietary linoleic acid decreased beta-oxidation of saturated fatty acids. These results indicate that metabolic differences between 18:0 and 16:0 only partially explain the difference in the cholesterolemic effect reported for these saturated fatty acids.

PMID: 7977144

The results of these stable-isotope studies in male subjects indicate that desaturation of 18:0 is ~2.4-fold higher than desaturation of 16:0 (9.2% vs 3.9%). Total plasma lipid contained ~12% more 16:0 than 18:0. Percent absorption of 18:0 was ~7% lower than that for 16:0. Differences in fl-oxidation of 16:0 and 18:0 cannot be reliably compared on the basis of the carbon- 13 isotope studies that have been published. These data suggest that no single metabolic difference between 16:0 and 18:0 is sufficiently large enough to fully explain the lower cholesterolemic effect of stearic acid. However, an accumulation of relatively small differences between 16:0 and 18:0 metabolism (absorption, desaturation. and acylation) does have merit as at least a partial explanation for why 18:0 is less hypercholesterolemic than 16:0.

Edited by niner, 01 June 2013 - 03:58 PM.