Food Components to Enhance Performance An Evaluation of Potential Performance-Enhancing Food Components for Operational Rations (1994) / Chapter Skim
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18. Structured Lipids: An Overview and Comments on Performance Enhancement Potential
18. Structured Lipids: An Overview and Comments on Performance Enhancement Potential
Pages 351-380
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From page 351... ...
The potential use of structured lipids in diets intended to enhance performance is examined in this chapter in light of the current understanding of fat metabolism and the relatively small amount of information now available on the specific use of structured lipids in performance enhancement. The primary focus of research with structured lipids has been in the areas of parenteral and enteral nutritional regimens for the stresses caused by surgery, burns, and trauma.
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From page 352... ...
. The metabolism of these mixed fatty acid triacylglycerols, known as structured lipids, has been compared with that of typical LCTs (Figure 18-1~.
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From page 353... ...
The coarse emulsion of fat is converted into a much finer dispersion of oil droplets through mechanical mixing and the reduction of interracial tension as bile salts, and phospholipids are introduced through gallbladder contraction. This dispersion of fat greatly increases the interracial area where pancreatic lipase can act to catalyze the hydrolysis of the triacylglycerol into the 2-monoacylglycerol and fatty acids from the 1 and 3 positions of the glycerol.
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From page 354... ...
There is no absorption through the assimilation of intact oil droplets by pinocytosis (Cardell et al., 1967~. Although pancreatic lipase hydrolyzes fat only in the 1 and 3 positions of the molecule, it is nevertheless possible for fatty acids in the 2 position of the triacylglycerol to be hydrolyzed.
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From page 355... ...
, and capric (decanoic) acids are the source of the unique properties of structured lipids.
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From page 356... ...
This rapid hydrolysis is the key event that provides the unique behavior both of MCTs and of structured lipids. MCTs are readily hydrolyzed, arid their digestion products are caprylic acid, capric acid, and the 2-monoacylglycerols of these acids.
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From page 357... ...
MCT fatty acids are only sparingly found in the lymph, and there they are found only as a trace component of a mixed triacylglycerol with two long-chain fatty acids and one medium-chain fatty acid. The aqueous solubility of the MCT fatty acids causes them to enter the portal circulation bound to albumin for direct transport to the liver (Hashim, 1968)
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From page 358... ...
. with the liver is an important deviation from LCT metabolism, where the LCTs in chylomicrons reach the liver only after a significant portion has been hydrolyzed by lipoprotein lipase for delivery of fatty acids to peripheral tissues.
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From page 359... ...
The lipogenesis from MCTs is an inefficient process with little elongation of the octanoate and, principally, the production of the acetate that is used in the de nova synthesis of fatty acids. The feeding of MCTs to animals results in virtually no deposition of octanoic and decanoic acids in the carcass or adipose tissue (Jandacek et al., 1991~.
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From page 360... ...
In particular, structured lipids with omega-3 fatty acids have been synthesized and investigated, so a review of the properties of this class of fatty acids is relevant to an understanding of structured lipids. The omega terminology for fatty acids is based on the number of carbon atoms from the terminal methyl carbon to the first double bond of the hydrocarbon chain.
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From page 361... ...
1 - 2 H 22:6 (4,7,tO,13,16,19) docosahexaenolc FIGURE 18-7 The metabolism of omega-9, omega-6, and omega-3 fatty acids.
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From page 362... ...
There is also the possibility that under certain stress situations, minimization of linoleic acid's activity through an appropriate dietary omega-3/omega-6 fatty acid ratio may be beneficial. Some studies with structured lipids have followed this general hypothesis (Teo et al., 1991~.
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From page 363... ...
As mentioned earlier, structured lipids are not new to the human gastrointestinal system, since a calculation based on the approximation of a random distribution of medium- and long-chain fatty acids would indicate that approximately 16 percent of triacylglycerols in butterfat and 38 percent of triacylglycerols in coconut oil have the compositions of MML and MEL, where M and L signify medium- and long-chain fatty acids, respectively. Among the first examinations of fat that was enriched with structured lipids was work reported in the mid-1950s and early 1960s.
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From page 364... ...
Two approaches have been taken to provide a more nearly physiological rate of hydrolysis: formulations that blend MCTs with LCTs in a mixture of the two fats and formulations based on structured lipids. These formulations were originally intended to deliver essential fatty acids and provide well-utilized energy.
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From page 365... ...
Structured lipids could hydrolyze as readily as MCTs and could reduce the level of pancreatic lipase required for hydrolysis and absorption of the fatty acids. The advantage of structured lipids over MCTs in this application would be the absorption of essential fatty acids as well as medium-chain fatty acids.
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From page 367... ...
367 Cal _ C | ~ ~ ~ TO ~ ~ ~ ~ ~ _ X ~ Ilk ~ E-^ - ^ c C ~ ~ ~ 3~0 ,< a O HI O ~ ~ C~ 5 -3 tt O Z Z Z Z Z ~ ~ Z ~ ~ ~ ~ E~ ~ ~ E~ o ~ ~ ~ ~ ~ 5 C C e ~ t i~ ~ C)
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From page 368... ...
MEDIUM-CHAIN FATTY ACIDS IN EXERCISE STUDIES The studies that are of most relevance to the topic of performance enhancement have not utilized structured lipids but have utilized MCTs. A review of those studies is of value, however, since normal, healthy subjects readily change a structured lipid into its fatty components.
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From page 369... ...
are hydrolyzed and probably rearranged to allow further hydrolysis. Structured lipids hydrolyze to give the same products that would be formed from mixtures of long-chain triacylglycerols (LCTs)
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From page 370... ...
The direct extrapolation of this conclusion to structured lipids is appropriate since the only unique fuel provided by structured lipids is the medium-chain fatty acid component. Medium-chain fatty acids from structured lipids follow the same digestion and absorption process as medium-chain fatty acids from MCTs (Webb and Sanders, 1991~.
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From page 371... ...
The use of MCTs in the nutritional treatment of lipase insufficiency continues to be a viable regimen. In addition, the use of structured lipids with appropriate levels of essential fatty acids may ensure the maintenance or development of a healthful essential fatty acid status.
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From page 373... ...
373 an I _ I _ _ ~ ant It 3 ~ 4)
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From page 374... ...
The reduced gastrointestinal distress and the production of medium-chain fatty acids by the digestion of structured lipids suggest that structured lipids would provide the same nutrients in a more acceptable form. · The chronic ingestion of structured lipids with appropriate levels of omega-3 and omega-6 essential fatty acids may provide optimum health in terms of platelet aggregation, inflammatory reactions, and the promotion of cancer.
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From page 375... ...
Bistrian 1988 Enhanced skeletal muscle and liver protein synthesis with structured lipid in enterally fed burned rats. Metabolism 37:787-795.
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From page 376... ...
1968 Studies of medium chain fatty acid transport in portal blood.
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From page 377... ...
Yamamota 1992 Effect of structured lipids as energy substrate after hepatectomy in rats with streptozocin-induced diabetes. Nutrition 8:41~6.
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From page 378... ...
That is what people found, but apparently, no one looked at the effect of medium-chain triglycerides or structured lipids in a situation with a more moderate exercise level. RONALD JANDACEK: I have not seen that.
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From page 379... ...
Again, I do not think that the mechanism is very clear, other than the mechanism for those with a vasoactive effect, these omega-3 fatty acids and also an effect on the eicosanoids, that the omega-3 fatty acids do reduce the eicosanoid production that is normally seen from omega-6 fatty acids or arachidonic acid. CAROLE GREENWOOD: Question about cholesterol metabolism and structured lipids.
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