In the early days of nutritional science, dietary fiber did not attract attention because it was considered to have no nutritional value. Later, however, it was found that dietary fiber had both nutritional and physiological effects that ordinary nutrients lacked, and was an indispensable food ingredient for maintenance of health. Currently, there is still no general consensus on the definition and classification of dietary fiber, or on the optimal method for analyzing it. In the course of research on analysis of dietary fiber, it became clear that one type of starch is not digested in the small intestine, and this is now known as resistant starch. Resistant starch was shown to have the same nutritional and physiological effects as dietary fiber, which are influenced by physical and chemical properties such as viscosity and bulking effects. Dietary fiber and resistant starch are now being applied to the development of foods for prevention of lifestyle-related diseases.

View full abstract

In view of the increasing incidence of arteriosclerosis and coronary heart disease caused by hypercholesterolemia, some food components are receiving attention because of their ability to normalize cholesterol metabolism. In this study we examined the mechanisms by which dietary fiber and taurine reduce the plasma cholesterol concentration by focusing on their effects in the digestive tract. We found that sugar beet fiber (BF), which is a high-fermentative dietary fiber, lowered plasma cholesterol concentrations in rats, and that passage through the lower digestive tract, especially the cecum, was necessary for initiating this effect. Moreover, the effect was related to fermentation of BF in the large intestine. The by-products of fermentation that induce this effect have not yet been determined. However, in addition to fermentation of BF in the large intestine, increased bile acid excretion into feces is critical for induction of the plasma cholesterol-lowering effect. We also confirmed that bile acid excretion into feces enhanced by taurine feeding plays a role in the plasma cholesterol-lowering effect. The inhibition of bile acid absorption, but not the induction of cholesterol 7α-hydroxylase, seems to be related mainly to an increase of bile acid excretion induced by taurine. Our findings indicate that the reduction of plasma cholesterol concentrations results from fermentability of dietary fiber in the lower digestive tract and inhibition of bile acid absorption from the distal ileum and lower digestive tract by taurine.

View full abstract

Most patients with atopic dermatitis suffer from dry skin, deterioration of epidermal barrier function, and dermatitis. Hairless mice (HR-1) are a well known animal model for studies of skin abnormalities such as atopic dermatitis. Atopic dermatitis-like symptoms can be induced in these animals by feeding them a specific diet, known as the HR-AD. Using this animal model, we examined the effects of oral administration of an ethyl alcohol extract of tamogi-take, an edible mushroom that contains a high concentration of glucosyl ceramide (hereafter referred to as tamogi-take extract), on atopic dermatitis. The control group (HR-AD-fed mice) showed typical atopic dermatitis, with gradual transepidermal water loss (TEWL), keratinization and cellular infiltration into dermis. However, these conditions were ameliorated in the mice fed the tamogi-take extract (oral administration weight % of tamogi-take extract: 0.1% and 0.01% as glucosyl ceramide). Thus, in this study using hairless mice, epidermal barrier dysfunction induced by HR-AD was shown to be ameliorated by oral administration of tamogi-take extract.

View full abstract

Biotin is contained in a wide variety of foods. However, the 5th Revised Japanese Standard Food Table does not include the biotin content of foods, nor does it consider the loss of biotin resulting from food processing and cooking, or the bioavailability of biotin. Therefore, we determined the biotin contents of 330 typical foods available in Japan, and compared them with those of foods available in various other countries. The content of biotin found in peanuts, red peppers, liver (pork and chicken), egg yolk, instant coffee (powder), yeast (dried) and royal jelly exceeded 50 μg/100 g. With regard to various food groups, nuts, mushrooms and meats (including liver) contained, on average, a large amount of biotin, whereas fruits and oils contained only a small amount. Although the biotin content differed according to the method of analysis and the form of the foods, there were no marked differences in the biotin content of foods between Japan and other countries.

View full abstract