Wissenschaftliche Hintergrundinformationen zu den Ernährungs-Eigenschaften von ungehärtetem Kokosfett (Diese Liste wird laufend fortgeführt)

1) Studie zu mittelkettigen gesättigten Fettsäuren: A Geliebter, N Torbay, EF Bracco, SA Hashim and TB Van Itallie, Overfeeding with medium-chain triglycerides diet results in diminished deposition of fat. American Journal of Clinical Nutrition, Vol 37, 1-4, Copyright © 1983 by The American Society for Clinical Nutrition, Inc Abstract: The study was designed to determine whether overfeeding rats with a diet containing medium-chain triglyceride (MCT) as the major fat source (45% of calories) would impede the expected gain in weight and body fat as compared to rats overfed with isocaloric amounts of diet containing long-chain triglyceride (LCT). For 6 wk rats were fed either MCT diet or LCT diet twice daily via a gastrostomy tube. MCT-fed rats gained 20% less weight (P less than 0.001) and possessed fat depots weighing 23% less (p less than 0.001) than LCT-fed rats. Mean adipocyte size was smaller (p less than 0.005) in MCT- than in LCT-fed rats. Weights of carcass protein and water were similar for both groups as were concentrations of serum insulin and levels of physical activity. The decreased deposition of fat in the MCT-fed rats may have resulted from obligatory oxidation of MCT-derived fatty acids in the liver after being transported there via the portal vein, leaving almost no MCT derivatives for incorporation into body fat. MCT may have potential for dietary prevention of human obesity.

2) Die „Verbrennung“ ist bei mittelkettigen gesättigten Fettsäuren um 12% gesteigert, gegenüber 4% bei langkettigen gesättigten Fettsäuren.

3) Studie zu thermischen Wirkungen von mittel- und langkettigen gesättigten Fettsäuren auf den Menschen: Seaton T., Welles S.,Warenko W.,Thermic effects of MCT and LCT in man, American Journal of Clinical Nutrition 1986; 44, 630-634

4) verschiedene Kapitel zu gesättigten Fettsäuren im Buch ?Fat That Heals, Fat That Kills?, Udo Erasmus, Alive Books, Revised, updated & expanded 1993, ISBN-10: 0920470386

5) Fat metabolism, article discussing the specifications of MCT oil, why we use it and how it works, by Arthur E. Roberson, Ph.D

I. Introduction
Nomenclature of Fats

Fats, or lipids, are found in all cells and perform a variety of functions essential for life. These include their roles in energy storage, membrane structure, and incorporation in vitamins, hormones, and prostaglandins (Zubay, 1983). Fats are used to cushion and insulate the body and function as electrical insulation in the nervous system. Triglycerides are the most common form of fat found in foods and stored in body fat depots. Most naturally occuring triglycerides contain fatty acids 16-20 carbon atoms in length. Such fatty acids are called ?long chain fatty acids? (LCFAs), and their corresponding triglycerides are called ?long chain triglycerides? (LCTs). Medium chain triglycerides (MCTs) are comprised of medium chain fatty acids (MCFAs), which are 6-12 carbons in length. Although the carboxylic acid part of fatty acids is soluble in water, the hydrocarbon chain is not. Thus, LCFAs are not water soluble. Since the hydrocarbon chains of MCFAs are shorter, MCFAs are more water soluble than LCFAs. Likewise, MCTs are also relatively soluble in water, due to ionization of the carboxylic acid groups and the small size of the hydrocarbon chains. Their small molecular size and greater water solubility cause MCTs to undergo a different metabolic path than that experienced by LCTs (Bach and Babayan, 1982).

Occurrence and Purification of MCTs
Medium chain triglycerides occur naturally in small quantities in a variety of foods, and are present naturally in the blood of the human fetus and in human milk (Bach and Babayan, 1982; Souci, Fachmann, Kraut, 1989/90)? MCT oil has a caloric density of 8.3 calories per gram; one tablespoon equals 14 grams and contains 115 calories. MCTs are not drugs and have no pharmacological effects (Bach and Babayan, 1982).

Historical Uses of MCTs
Since their introduction in 1950 for the treatment of fat malabsorption problems, medium chain triglycerides have enjoyed wide application in enteral and parenteral nutrition regimens (Bach and Babayan, 1982). Fat emulsions can be used to provide up to 60% of nonprotein calories. Before the availability of lipid emulsions suitable for intravenous use, glucose was used as the only nonprotein source of calories (Mascioli et al, 1987). Not only did this result in essential fatty acid deficiencies, but it was also undesirable because it increased hepatic lipogenesis and respiratory work. Although inclusion of LCTs in intravenous feedings represented an improvement, problems remained with slow clearance of LCTs from the bloodstream and interference with the RES component of the immune system. When medium chain triglycerides or structured lipids (triglycerides containing both MCFAs and LCFAs) are added to the regimen, calories are provided in a more readily oxidizable form (Schmidl, Massaro, and Labuza; 1988), and less interference with the RES is observed (Mascioli et al, 1987). In one case, MCT was fed as the exclusive source of fat (along with a small amount of LCT to provide essential fatty acids) to a patient with chyluria (a fat malabsorption disease) for over 15 years without producing side effects (Geliebter et al, 1983).

Sports Nutrition
Although MCTs have been used in hospital environments for years, their use by healthy individuals is relatively new. Recently, athletes have begun to use MCTs to increase caloric consumption, thereby providing energy and facilitating weight gain. Their low food efficiency, due to the thermogenic effect, means that MCTs have very little tendency to be converted to body fat. The calories from MCTs represent an additional energy source which (in contrast to conventional fats) can be used concurrently with glucose.

II. Metabolism
Digestion and Absorption of Fats

Since LCTs are not very soluble in water, the body has to go through an elaborate digestive process in order to absorb these nutrients. Bile salts are secreted by the gall bladder to help dissolve the LCTs. Upon ingestion, LCTs interact with bile in the duodenum (upper small intestine) and are incorporated into mixed micelles (Record et al, 1986). Enzymes called lipases (pancreatic lipase and phospholipase A2) remove the fatty acid molecule from the glycerol backbone. The mixed micelles are passively absorbed into the intestinal mucosa where the free fatty acids are re-esterified with glycerol. The intestinal mucosa synthesizes a lipoprotein carrier called a chylomicron to transport the reformed triglyceride. Chylomicrons are secreted into the lymph and are released into the venous circulation via the thoracic duct. In the bloodstream, lipoprotein lipase again breaks down the triglycerides into two free fatty acids and a monoglyceride. The monoglycerides go to the liver to be further degraded, while many of the circulating free fatty acids are taken up and stored by adipocytes (fat cells). When carbohydrates are consumed insulin is released, and insulin stimulates adipocytes to re-esterify the fatty acids into triglycerides and store them as body fat. In general, body fat stores are not mobilized and used for energy to any significant extent in the presence of insulin.

In contrast, since MCFAs are more water soluble they are more easily absorbed and do not require this complicated digestive process. MCTs can be absorbed intact and do not require the action of pancreatic lipase or incorporation into chylomicrons. Instead, a lipase within the intestinal cell degrades the MCT into free MCFAs and glycerol. The MCFAs are bound to albumin, released into the bloodstream, and transported directly to the liver by the portal vein. The vast majority of MCFAs are retained by the liver where they are rapidly and extensively oxidized. Whereas conventional fats are largely deposited in fat cells, MCTs are transported directly to the liver and used for energy. Very little of the MCFAs ever escape the liver to reach the general circulation (Bach and Babayan, 1982). Only 1-2% of MCTs are incorporated into depot fat (Geliebter et al, 1983; Baba, Bracco, and Hashim, 1982). Medium chain triglycerides are digested and absorbed much faster than conventional fats (in fact, as rapidly as glucose) and are immediately available for energy.

References
1. Baba, Bracco, and Hashim, Enhanced thermogenesis and diminished deposition of fat in response to overfeeding with diet containing medium chain triglyceride. Am. J. Clin. Nutr. 35: 678-682 (1982).
2. Bach and Babayan, Medium chain triglycerides: an update. Am. J. Clin. Nutr. 36:950-962 (1982).
3. Christensen, Hagve, Gronn, and Christophersen, Beta-oxidation of medium chain (C8-C14) fatty acids studied in isolated liver cells. Biochem. et Biophys. Acta 1004: 187-195 (1989).
4. Geliebter, Torbay, Bracco, Hashim, and Van Itallie, Overfeeding with medium chain triglyceride diet results in diminished deposition of fat. Am. J. Clin. Nutr. 37: 1-4 (1983).
5. Mascioli, Bistrian, Babayan, and Blackburn, Medium chain triglycerides and structured lipids as unique nonglucose energy sources in hyperalimentation. Lipids 22: 421-423 (1987).
6. Record, Kolpek, and Rapp, Long chain versus medium chain length triglycerides – a review of metabolism and clinical use. Nutr. Clin. Prac. 1:129-135 (1986).
7. Schmidl, Massaro, and Labuza, Parenteral and enteral food systems. Food Tech. 77-87 (July, 1988).
8. Souci, Fachmann, and Kraut, Food Composition and Nutrition Tables 1989/90. Published by Wissenschaftliche Verlagsgesellschaft (1989).
9. Sucher, Medium chain triglycerides: a review of their enteral use in clinical nutrition. Nutr. Clin. Prac. 44: 146-150 (1986).
10. Zubay, Biochemistry, chapter 13: ?Metabolism of Fatty Acids and Triacylglycerols,? by Denis E. Vance. Published by Addison-Wesley Publishing Company (1983).