Dietary fat and the fat stored on our body as adipose tissue are in the form of triglycerides, which contain long-chain fatty acids (14 carbons or more) [1]. The most prevalent fatty acids found in food are oleic (C18:1), palmitic (C16:0), stearic (C18:0), and linoleic (C18:2). Due to molecular distillation in the early 1960's, it became possible to prepare a mixture of triglycerides that contain only medium-chain fatty acids (MCFA; 6-12 carbons). MCFA's are naturally found in coconut oil, palm kernel oil, and milk.
Medium-chain triglyceride (MCT) oil is comprised of primarily caprylic (C8:0) and capric (C10:0) acids with a very small percentage of caproic (C6:0) and lauric (C12:0) acids, which are esterified to a glycerol backbone. MCT oil is a light yellow, translucent, odorless liquid at room temperature (MCT's are also available in powder form). Although completely saturated, it is not atherogenic [2] or solid in consistency like other saturated fats, due to the shorter chain lengths of the fatty acids within the oil.
The energy value of MCT oil is approximately 7-9 Calories per gram, and this fat is metabolized differently than long-chain triglycerides (LCT). Complete hydrolysis to MCFA's and small amounts of monoglycerides occurs in the stomach with very little secretion of pancreatic lipase or bile acids. After MCFA's are absorbed into the intestinal mucosal cells, they are not resynthesized into triglycerides and incorporated into chylomicrons as are long-chain fatty acids. MCFA's bypass the lymphatic system and are carried by the portal vein directly to the liver, where they are metabolized to produce carbon dioxide, ketones, and acetate.
Therapeutic uses
Due to the unique properties of MCT's, they are used as a fat source in many disease states. MCT oil can be used to add calories to a formula or diet in the case of malabsorption syndromes. Due to a more rapid digestion and absorption, MCT's increase the osmolality of formulas. Since it requires lower concentrations of bile or pancreatic lipase for digestion and absorption, patients with bile acid and pancreatic lipase deficiencies benefit from adding this fat source to the diet. MCT's comprise the lipid component in many infant formulas because infants rely on lingual lipase for lipid digestion when pancreatic function is not fully developed.
MCT's are contraindicated for people with diabetes, due to the risk of hyperketonemia. MCT's are also generally not recommended for people who have compromised hepatic function because a diseased liver does not have the ability to clear the increased levels of MCFA's. Essential fatty acids and fat-soluble vitamins must be added to MCT oil if it is a significant source of fat in the diet.
MCT oil is also unpalatable for some people and may cause diarrhea when it is consumed in large amounts (for people who experience GI distress, small amounts throughout the day promote greater tolerance). The high cost of MCT oil is another limitation to its use in the diet. These factors should be addressed by the dietitian or physician after it is determined whether a client or patient can benefit from MCT oil.
Alternative uses
Besides being used to alleviate the effects of malabsorption syndromes, MCT's have some nontraditional applications. The ketogenic diet has been effective in treating chronic seizures. MCT's are used to induce ketosis in these patients.
When MCT's are substituted for long-chain triglycerides in the diet, animals gain less weight, store less adipose, and experience an increase in metabolic rate [3, 4, 5]. MCT-fed mice also have been shown to possess increased endurance over that of LCT-fed mice [6]. It is probably these factors that have brought MCT oil into the market of ergogenic aids and dietary supplements. Due to the caloric value of MCT oil, it can be effective in adding energy to the diet.
There is far less research conducted in human subjects, and the results from animal studies do not necessarily apply to humans. The amount of this fat that is consumed by animals to create a performance effect is far more than the average human consumption of fat. Nevertheless, it could be beneficial to substitute MCT oil for other oils that contain long-chain fatty acids, since scientific evidence indicates that MCT's may be less easily stored as adipose. Recipes using MCT oil have been published [7], and MCT oil can be substituted in place of most cooking oils.
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References
Babayan, VK (1987) Medium chain triglycerides and structured lipids. Lipids, 22(6), 417.
Blackburn, GL et al. (1989) A reevaluation of coconut oil's effect on serum cholesterol and atherogenesis. J. Phil. Med. Assoc., 65(1), 144.
Hashim, SA (1967) Medium chain triglycerides: Clinical and metabolic aspects. J. Amer. Diet. Assoc., 67(9), 221.
Baba, N et al. (1982) Enhanced thermogenesis and diminished deposition of fat in response to overfeeding with diet containing medium chain triglyceride. Amer. J. Clin. Nutr., 35(4), 678.
Geliebter, A et al. (1983) Overfeeding with medium-chain triglyceride diet results in diminished deposition of fat. Amer. J.
Clin. Nutr., 37(1), 1.
Fushiki, T et al. (1995) Swimming endurance capacity of mice is increased by chronic consumption of medium chain triglycerides. J. Nutr., 125(3), 531.
Schizas, AA et al. (1967) Medium chain triglycerides: Use in food preparation. J. Amer. Diet. Assoc., 67(9), 228.
* Looks good to me !
