The MCFAs are esterified with glycerol with or without a catalyst to form the triacylglycerols. The melting point of the MCFAs is much lower (C8:0 at 16.7 oC, C10:0 at 31.3 oC) than that of the longer-chain fatty acids (LCFAs) (C16:0 at 63.1 oC). Thus MCFAs, but also Medium-Chain Triacylglycerols are liquid at room temperature.
Thus MCFAs, but also Medium chain triacylglycerol, are liquid at room tempertaure. By virtue of their smaller molecular size MCFA are relatively soluble in water : the water solubility at 20 oC is 68 mg/100 ml for C8:0 versus 0.72 mg for C16:0. The fact that MCFA are weak electrolity and are highly ionic at neutral pH, increases even more their solubility in biological fluid.
The products of MCTs hydrolysis are absorbed faster than those of LCTs, and as fast as glucose (7). Since their intraluminal hydrolysis is rapid and relatively complete, the MCTs - unlike LCTs - are absorbed mainly as free fatty acids, and only rarely as monodiacylglycerols (Fig 1). In cases where bile salts or pancreatic lipase deficiency or both occur (8), a large fraction of MCTs can be absorbed as triacylycerols, whereas LCTs cannot be absorbed. In enterocytes, these MCTs are then hydrolyzed by an intestinal lipase.
In the mocusa, LCFA are converted into acyl-CoAs in the presence of an acyl-CoA synthetase. The acyl-CoAs are then incorporated into triacylglycerols, which are a major component of chylomicrons. Since this enzyme is specific for fatty acids with more than 12 carbon atoms, the MCFAs are not significantly incorporated into cylomicrons; therefore, MCFAs leave the intestine faster than the LCFAs. The tendency of fatty acids to be esterified is directly proportional to their ability to bind to fatty-acid-binding protein (9,10). MCFAs are not easily bound to this protein and are not easily esterified, while LCFAs are easily bound to this protein and incorporated abundantly into lipids.
MCFAs follow the portal venous system (Fig 1), whereas LCFAs follow the lymphatic system. Thus, MCTs do not stimulate the flow of lymph, while LCTs stimulate it significantly. The LCFas are transported as chylomicrons, which are insoluble particles. The MCFas, however, are transported in the soluble form of fatty acids, bound to serum albumin. This bond between MCFAs and albumin, however, is not as easily formed as that between LCFAs and albumin (11).
Because MCFAs leave the intestinal mucosa by the portal venous system, they reach the liver more rapidly then the longer molucules. The latter move via the extrahepatic tissues, where they may be partially retained. Thus, MCFAs reach the liver in greater abundance than do exogenous LCFAs. The majority of the MCFAs is retained in the liver, and only a small amount appears in the peripheral blood for a short periode of time
The mode of transport of MCFAs result in reduce sterol absorption (13). To be absorbed, sterols must be incorporated into micelles; and to be transported they must be bound to LCFAs, and incorporated into chylomicrons (14). These two processes do not take place with MCFAs and consequenty the absorption of sterols is diminished.
The absorption of calcium (15) and magnesium appears to be enhanced when the diet contains MCTs, particularly in infants (16). The absorption of amino acids also appears to be improved (17, 18).
The Green Coco Island
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The Green Coco Island | Extra Virgin Coconut Oil
The Green Coco Island | Part II
The Green Coco Island | Coconut Water
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