Medium-chain triglycerides

Medium-chain fatty acids (MCFAs) comprise saturated fatty acids with 6-10 carbons. Besides synthetic medium-chain triglyceride (MCT) oils there are natural sources, like coconut oil and dairy fat. Compared with long-chain fatty acids (LCFAs), the chemical and physical properties of MCFAs show substantial metabolic differences. MCFAs do not require binding to proteins such as fatty-acid binding protein, fatty acid transport protein, and/or fatty acid translocase (FAT, homolog to human platelet CD36). MCFAs are a preferred source of energy (beta-oxidation). MCFAs are also incorporated into adipose tissue triglycerides, and may influence adipose tissue and other systemic functions more substantially than previously assumed. MCTs reduce fat mass, through down-regulation of adipogenic genes as well as peroxisome proliferator activated receptor-gamma. Recent studies confirmed the potential of MCFAs to reduce body weight and particularly body fat. This effect was not transient. MCFAs reduce lipoprotein secretion and attenuate postprandial triglyceride response. It was, however, frequently observed that MCTs increase fasting cholesterol and triglyceride levels. But, given in moderate amounts, in diets with moderate fat supply, MCFAs may actually reduce fasting lipid levels more than oils rich in mono- or polyunsaturated fatty acids. The same is true for glucose levels. MCTs improved several features contributing to enhanced insulin sensitivity. Under certain in vitro conditions, MCTs exert proinflammatory effects, but in vivo MCTs may reduce intestinal injury and protect from hepatotoxicity. (c) 2006 Elsevier Ltd. All rights reserved.