266 December 2010, Vol. 22, No. 12 Lipid Technology Feature Bioactivity and emerging role of short and medium chain fatty acids Peter J. Huth, Victor Fulgoni, III, Ronald J. Jandacek, Peter J. Jones, Marie-Pierre St-Onge, and Vijitha Senanayake P.J.H. is consultant at PJH Nutritional Sciences, Menomonie, WI 54751, Phone (847) 541-6309; E-mail huthpj@gmail.com V.F. is Sr. Vice President at Nutrition Impact LLC, Battle Creek, MI R.J.J. is Adjunct Professor at Department of Pathology, University of Cincinnati, Cincinnati, OH P.J.J. is Professor and Director at Richardson Centre for Functional Foods and Nutraceuticals, University of Manitoba, Winnipeg, Manitoba, Canada M-P.S. is Research Associate at New York Obesity Research Center, St. Luke's/Roosevelt Hospital Center, New York, NY 10025 and Assistant Professor at Columbia University, New York, NY 10036 V.S. is Research Associate, Richardson Centre for Functional Foods and Nutraceuticals, University of Manitoba, Winnipeg, Manitoba, Canada Summary Cardiovascular disease (CVD) and insulin resistance are directly linked to overweight and obesity. Thus, any dietary strategy capable of causing weight reduction will lower CVD and diabetes risk. Oils rich in medium-chain saturated fatty acids (MCFA) are among several dietary components that may have potential in the treatment of obesity. MCFA are less energy dense and highly ketogenic compared to long- chain saturated and unsaturated fatty acids (LCFA). MCFA also differ from LCFA in theirdigestive and metabolic pathways, since they are easily oxidized and utilized as energy, with little tendency to deposit as body fat. The dietary intake of short (SCFA) and medium-chain saturated fatty acids from natural food sources is approximately 2.4 g/day and accounts forabout 9% of the total saturated fatty acid (SFA) intake. Although early clinical studies with high levels of MCFA resulted in increased levels of plasma triacylglycerols (TAG) and low- density lipoprotein cholesterol (LDL-C), and reduced levels of high-density lipoprotein cholesterol (HDL-C) compared to diets enriched in unsaturated LCFA, these adverse effectshave not been observed in more recent studies with smaller more realistic amounts of MCFA. The lowercaloric value of SCFA and MCFA and their unique metabolic features form the basis for theirclinical use in enteral and parenteral nutrition and for novel reduced calorie lipids for use in conventional food products. Introduction Medium-chain triglycerides (MCT) are composed of MCFA with 6–12 carbons. In typical Western diets, the predominant SCFA and MCFA consist of 4:0 and 6:0–12:0, respectively. Dietary intake data from the 2007–2008 National Health and Nutrition Examination Survey (NHANES) show that adult males and females consume an average of 2.62 and 2.13 g/day, respectively, of SCFA and MCFA (Table 1). These fatty acids account for approximately 8.3 and 9.5% of the total saturated fatty acid intake of men and women, respectively. Although these fatty acids represent a relatively small proportion of the total SFA intake, results from a large cohort of women showed that unlike saturated LCFA, intakes of 4:0–10:0 SFAs were not associated with CHD risk [1]. While it is understood that the majority of dietary SCFA and MCFA, are derived from animal food sources, there are little data on the contribution of specific food pro- ducts. We recently assessed the contribution of individual food groups to the intake of SCFA and MCFA in the U.S. diet using the NHANES 2003–2006 dataset. Individual foods were classified by their main ingredient into 9 pre-established food groupings (Table 2). These data showed that dairy products were the pri- mary contributors to the intake of SCFA and MCFA accounting for 56.8% and 58.0% of their intake, respectively. MCFA behave differently from LCFA in every aspect of metabo- lism from absorption to catabolism. MCFA are more water solu- ble than LCFA and are solubilized in the aqueous phase of intes- tines without forming micelles, therefore undergoing faster absorption than LCFA. Subsequent to absorption, MCFA are secreted directly into the portal circulation without undergoing re-esterification in the enterocyte. Due to their water solubility, MCFA do not require albumin for transportation from capil- laries to peripheral tissues. Similar to LCFA, MCFA also undergo b-oxidation in mitochondria but do not require carnitine for mitochondrial transport. All of these factors result in rapid metabolism of MCFA from ingested MCT and form the basis for their use in clinical nutrition and parenteral nutrition as well as their emerging role in weight management. MCTs and weight management MCT are being increasingly recognized for their effects in enhan- cing energy expenditure and reducing adiposity. Results from many animal and human studies show that MCT consumption leads to a reduction in weight gain and adiposity. Decreased adiposity after MCT or MCFA feeding was reported in several mouse and rat studies. Decreased adipocyte size was associated with lower adiposity in rats fed 20% MCT vs similar dietary levels of long chain triacylglycerols (LCT) from rapeseed oil. Increased levels of circulating adiponectin and increased area under the curve (AUC) in oral glucose tolerance test was also observed in i 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.lipid-technology.com DOI 10.1002/lite.201000071