The objective of this study was to investigate eŠects of dietary medium-chain triacylglycerols (MCTs) on serum lipid levels, liver function, and hepatic fat accumulations in healthy men. Eleven subjects consumed 2200-2600 kcal daily, of which 70-80 g was fat; the fat included 40 g of MCTs or else 40 g of long-chain triacylglycerols (blended vegetable oil). The diet was followed for 4 weeks in this controlled double-blind study. At the end of the experiment, signiˆcant diŠerences were not found in the concentrations of serum total cholesterol, very low density lipoprotein cholesterol, low density lipoprotein cholesterol, and high density lipoprotein cholesterol between the groups. Serum triglycerol levels were not signiˆcantly diŠerent in the groups. Adverse eŠects from ingestion of MCTs on liver functions, the liver-to-spleen ratio on computed tomography (an index of fatty liver), or results of blood tests were not seen. The results suggest that the long-term eŠects of dietary MCTs on serum cholesterol were similar to those of unsaturated fatty acids found abundantly in vegetable oil, and that consumption of MCTs in the amount of 40 g W day for a month does not cause liver fat accumulation or liver dysfunction.

SummaryEffect of triacylglycerols containing medium and long-chain fatty acids (TML) on body fat accumulation was studied in rats. Male Wistar rats were fed an experi mental diet containing 25% soybean oil or TML for 6 weeks. The food intake for 6 weeks did not significantly differ between the two diet groups. However, the perirenal and mesenteric adipose tissue weight and carcass fat content were significantly lower in the TML diet group than in the soybean oil diet group. The epididymal adipose tissue weight and liver triacyl glycerol content did not significantly differ between the two diet groups. The digestibility of dietary fat did not significantly differ between the two diet groups. These results suggest that an intake of TML decreases body fat accumulation compared to an intake of soybean oil in rats. Key Words body fat accumulation, triacylglycerols containing medium and long-chain fatty acids, dietary fat, transesterification, rats Medium-chain triacylglycerols (MCT) are edible oils that consist of C8 and Cl0 saturated fatty acids. MCT were introduced to clinical nutrition in the 1950s for dietary treatment of malabsorption syndromes caused by rapid absorption (1). MCT were metabolized differ ently from long-chain triacylglycerols (LCT). Quite a few animal experiment studies have provided evidence that MCT diets lead to less body fat deposition compared to LCT diets (2-7). These results suggest that substitu tion of MCT for LCT in dietary fat could reduce dietary obesity if energy intake remained constant (1). MCT may have such a strong point, but utilization of MCT as cooking oil is limited. MCT are not good for high-tem perature cooking because of the lower smoking temper ature.Triacylglycerols containing medium and long-chain fatty acids (TML) are lipids that contain medium and long-chain fatty acids in the same triacylglycerol, and are made by transesterification of MCT and LCT. The smoking temperature of TML is higher than physical mixtures of MCT and LCT. TML are superior for high temperature cooking to physical mixtures of MCT and LCT.From the 1980s, studies have dealt with the effect of dietary TML on safety and whole body lipid oxidation. TML were rapidly oxidized compared with LCT in post operative patients and were not associated with any side effects (8). Recently, we have demonstrated that total energy expenditure was higher after TML inges tion than after LCT ingestion in healthy young women (9).

We describe a method developed to quantify the amount of foam in frying oils. In this method the foam was quantified by digitizing photographic images that were taken continuously at 1-s intervals; spots showing more than a certain luminance were considered as foam. The ratio of total foaming area to the whole oil surface was integrated to obtain the integration of foam (IF) index as a parameter of the extent of foaming. There was a good correlation between this method and the visual evaluation done by a group of panelists. Furthermore, the foaming tendency correlated with the distribution of TG by M.W. when the IF was plotted against the foam index of TG (FIT), which reflects the M.W. distribution. A correlation was found between the FIT value of oil and foaming on frying, indicating that when the FIT value is small, the oil foams less. Based on the results of this investigation, we have designed a method to obtain edible oils consisting of medium-chain FA that not only are nutritious but also have good cooking properties.Paper no. J10420 in JAOCS 80, 471-474 (May 2003).Since the discovery by Bloom et al.(1) in 1951 that mediumchain FA, unlike long-chain FA, are transported to the liver via the portal vein after their absorption in the small intestine, there have been extensive studies on the nutritious effect of FA (2-4). Because of the nutritional advantage of mediumchain FA, they have been used in the medical field as therapeutic agents for improving lipid absorption. It has been confirmed that medium-chain FA are highly stable and possess superior nutritional value compared to long-chain FA, because they are more readily convertible to energy. However, using these medium-chain FA in cooking oil is problematic. For example, when medium-chain TG oil (MCT) consisting solely of medium-chain FA is used for frying, it smokes; when it is used in combination with long-chain FA, it behaves violently, bubbling over with the consequent risk of fire. To design edible oils having the nutritional value of mediumchain FA, it is necessary to evaluate foaming quantitatively and to determine suitable TG lacking the tendency to foam.Many authors have investigated the foaming properties of deteriorated oils by focusing on the oxidative polymerization and thermal denaturation of FA, as well as on the effect of polar compounds on the tendency to foam (5-7). Although the relationship between the structure of TG and foaming was also investigated, that study focused on the foaming tendency of deteriorated oils used for frying for long periods of time (8). As yet, only one study has been conducted on the increased foaming tendency caused by the presence of mediumchain FA, and it is limited to the recognition that foaming increases when coconut oil is mixed with other oils (9).Furthermore, although other researchers have investigated the foaming mechanism when frying (10,11), there are no reports on the relationship between the tendency to foam and the structure of TG, especially among oils consisting of medium-chain FA. Moreover, few...