As L-arabinose is known to selectively inhibit intestinal sucrase activity, it may improve the obesity caused by excess sucrose ingestion. The effects of L-arabinose on energy expenditure and muscle fiber composition were studied using Otsuka Long Evans Tokushima Fatty (OLETF) rats that were fed either a 20% sucrose diet (C) or a 20% sucrose diet containing 1.5% L-arabinose (A) for 21 weeks. At 29 weeks of age, the abdominal adipose tissue weight and cell size were increased in group C, while the increase of weight and cell size were significantly inhibited in group A. L-arabinose also significantly suppressed the increase of blood glucose at 2h after glucose administration. The energy percentage of fat consumed in group A increased by 12.8% when estimated by RQ. The number of type I fibers was significantly increased in the rectus lemons muscle, which-like many other skeletal muscles-is composed of mixed type I and II fibers. These results suggest that L-arabinose is effective for changing the skeletal muscle fiber composition from predominantly glycolytic to oxidative, thus inhibiting the increment of abdominal adipose tissue. Such an altered muscle fiber ratio could improve type 2 diabetes mellitus.

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To investigate the influence of dietary fat content during the growth period on food choice of adult rats, three groups of male Sprague-Dawley rats (3 weeks of age) were fed either a standard diet (SD group), a low-fat diet (LFD group) or a high-fat diet (HFD group). After 9 weeks, 6 rats in each group were sacrificed and the remaining rats were placed on a self-selection regimen of LFD and HFD for 3 weeks. No significant difference in body weight was observed among these three groups during the experimental period. However, perirenal and epididymal fat tissue weights in the HFD group were highest and those in the SD group were lowest. The amount of LFD intake/total intake in the LFD group was 38-49%, that in the HFD group about 20%, and that in the SD group increased from 16 to 47% during the self-selection period. Therefore, dietary fat content during the growth period affects preferential fat intake in adult rats.

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A preliminary study was conducted to classify brown rice by geographical origin using trace element concentrations. Twenty-six types of rice from 23 different prefectures were digested in nitric acid under microwave irradiation. The digests were then analysed for their trace element contents using inductively coupled plasma mass spectrometry for 23 analytes, and the geographical features were observed in the concentrations of 18 analytes. The data obtained from these results were then analysed using SPSS, a statistical software package. Cluster analysis indicated that the composition of 5 analytes, Mg, Co, Ni, Te, and Au, represents the geographical origin of rice, such as the Tohkai-area, Kanto-Koshin-area and Kyushu-areas.

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Large-scale observations and intervention studies have indicated that the Japanese population should aim for a desirable cholesterol intake level in order to reduce disease incidence and mortality rate. In general, the amount of dietary cholesterol does not affect blood cholesterol concentration markedly, and the effects of dietary cholesterol on blood cholesterol concentrations depend on individuals. Japanese who are lean and take less saturated fat than Caucasians may show an increase in their LDL-cholesterol concentration when given a dietary cholesterol challenge. As shown in Caucasian populations and also in Japanese, either increased or decreased blood cholesterol concentrations are associated with higher mortality (U-shaped curve). The increased mortality observed in individuals with a high blood cholesterol concentration is due to increased LDL-cholesterol, which leads to atherosclerosis, whereas that observed in individuals with a low blood cholesterol concentration is considered attributable to malnutritional states such as cancer, lung disease, anemia, or infectious disease. Recent large-scale observation studies have indicated that an increased intake of cholesterol is not associated with an increased incidence of ischemic heart disease, apoplexy, or mortality, but in some studies, a positive linear association has been observed between cholesterol intake and the incidence of lung, pancreas, and colon/rectum cancer. Furthermore, considering the recently increased incidence of diabetes mellitus, which is a risk factor for ischemic heart disease and stroke, any increase of LDL-cholesterol concentration should be avoided. Thus, a higher intake of cholesterol is not recommended for the public at large.

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The purpose of this study was to characterize food melanoidin. Model melanoidin was prepared from glucose and amino acid, and the following methods were found to be available for the characterization of model and food melanoidins: electrofocusing, metal-chelating affinity chromatography, lectin affinity chromatography, oxidative and reductive conditions, preparative conditions, nutritional balance study in rats, and microbiological discoloration of brown pigments. The major precursors of fish sauce melanoidin and onion sauté melanoidin were found to be of the sugar type. Browning of freeze-dried tofu was caused by reaction between protein and unsaturated carbonyl compounds formed through autoxidation of lipids. The brown-colored materials were ether-soluble, weakly acidic, and reductone. Coffee melanoidin was formed by the Maillard reaction of sugar and amino acid to protein, involving oxidative degradation and polymerization of phenolic compounds such as chlorogenic acid and ferulic acid. Streptomyces werraensis TT4 (S), Paecilomyces canadensis NC-1 (P), and Coriolus versicolor IFO30340 (C) were cultured with browned foods and various types of model colorants. The colorants that exceeded the 50% decolorization rate for each microbe included P decolorized phenolic colorants such as coffee and black tea, C decolorized sugar-type model melanoidins, waste molasses, miso and soy sauce, and S decolorized caramel and sugar-type model melanoidins.

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Immune function helps to maintain the quality of life (QOL) in elderly subjects. However, age-associated thymic atrophy is reportedly related to alterations in the function of the immune system. Antioxidant status, in terms of parameters such as the activities of superoxide dismutase and glutathione peroxidase in thymocytes, is decreased in aged mice, suggesting that their thymocytes are more susceptible to oxidative stress than those of young mice. Intracellular reactive oxygen species (ROS) are reportedly involved in apoptosis when the cells are damaged by oxidative stress. To clarify the factors that can suppress the increase of intracellular ROS, we analyzed the antioxidant activities of 26 natural antioxidants and found that 13 of them, including flavonoids, eliminated the intracellular ROS induced by oxidative stress. On the other hand, protein known to influence immune function was taken almost equally in Japanese people in all ages. These results show that selective intake of antioxidants in addition to ordinary food may be useful for maintaining or improving the QOL of elderly individuals.

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The need for foods suited to elderly people has increased recently. This paper presents the characteristics of mastication in elderly individuals measured by electromyography (EMG), and some ideas on how to prepare such foods. Healthy elderly subjects exhibited lower EMG activity per chew and more chewing strokes with a longer mastication time than young people. This tendency was more significant for elderly individuals with poor dental status. The order of chewing difficulty for six different foodstuffs was common, regardless of age and dental status. Rice gruel required less mastication than the same weight of cooked rice, but a similar amount of mastication per 100 kcal. Thinly sliced cucumber required increased mastication per mouthful weight. These observations suggest that cooking food with a large amount of water and cutting food finely do not always ensure easy food mastication. Thus, we must obtain data for various kinds of food by measuring mastication in different human subjects.

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Using the Profile of Mood States (POMS) test, we collected data on the state of mind of elementary and junior high school students, who registered as markedly high on the Anger-Hostility (A-H) scale. The data were then cross-referenced with data from a survey of the subjects' food content. The high A-H group was found to have a generally lower dietary content of Japanese food materials. Using university students, further research was undertaken to investigate whether Japanese foodstuffs are healthier for both body and mind. The subjects were given healthy and balanced Japanese-style meals for five days. Analysis of blood samples showed an improvement in the levels of neutral fats in men and total cholesterol in women. POMS scores for high A-H, Tension-Anxiety, Depression-Dejection and Fatigue were also improved. We then evaluated the modulating effects of L-γ-glutamyl ethyl amide (teanin) in green tea and soy protein hydrolysate (soy peptides) chosen as Japanese food materials on human brain functions by investigation of cerebral blood flow and other non-invasive measurements. Oxy-Hb concentration and cerebral blood flow at the forehead determined by near infrared spectroscopy (NIRS) did not increase as compared with the placebo while performing assigned tasks when the subjects ingested teanin or soy peptides. Additionally, POMS scores were improved in the teanin group, and salivary cortisol was significantly lower after performing the tasks in the case of soy peptide ingestion compared with the placebo. These results suggest that ingestion of teanin or soy peptides affects brain activity and may decrease stress.

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This article reviews mainly our studies conducted over 40 years or more on neural regulation of nutrient, energy metabolism and energy expenditure by effective constituents of food flavors. (1) Direct neural regulation of nutrient metabolism in the liver was demonstrated by stimulation of the ventromedial hypothalamic (VMH)-sympathetic nervous system, which-independently of hormonal effects-caused glycogenolysis by rapid activation of glycogen phosphorylase, whereas stimulation of the lateral hypothalamic (LH)-parasympathetic nerve system resulted in glycogenesis by activation of glycogen synthase in the liver. Direct neural regulation of hepatic metabolism was further verified by studying perfused liver ex vivo; the involvement of neuropeptides and certain cytokines, in addition to noradrenaline (NA), in the mechanism of nerve-signal transmission was demonstrated. (2) Extension of studies on the central nervous system regulation of energy metabolism revealed that stimulation of the VMH-sympathetic nervous system causes not only lipolysis in white and brown adipose tissue (BAT), but also lipogenesis in BAT preferentially. This indicates that the VMH-sympathetic nerves enhance triglyceride synthesis and breakdown (i.e., turnover of triglycerides), which leads to heat production and energy dissipation unique to BAT. Disorder of this regulatory system in rats decreases the body's energy expenditure and leads to obesity. (3) Skeletal muscles comprise the major working tissue involved in resting-energy metabolism. It was demonstrated that VMH stimulation also enhanced glucose uptake and utilization in the heart, skeletal muscles and BAT selectively, through mediation of direct sympathetic innervation. Analysis of the mechanism underlying this sympathetic regulation revealed that the sympathetic neurotransmitter NA enhances glucose uptake independently of insulin, but possibly via β₃-adrenergic receptors and activation of GLUT-1 glucose transporters present in the plasma membrane. Microinjection of leptin into the VMH also increased glucose uptake into skeletal muscles through sympathetic facilitation as well as β-oxidation of fatty acids through a novel signaling pathway involving AMP-kinase. (4) It has been considered that some food flavors or spices promote energy expenditure by stimulating gustatory receptors coupled with sympathetic activation. In fact, the effective components of ginger and raspberry, zingerone and raspberry ketone, were shown to have stimulatory effects on energy expenditure by increasing oxygen consumption and decreasing the respiratory quotient, resulting in amelioration of the abnormal lipid metabolism induced by ingestion of a high-fat diet.

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