Scientific Program (Oral Abstracts) | Poster Abstracts | Speaker List
September 15-18, 1996
Brussells, Belgium
SCIENTIFIC PROGRAM
(Oral Abstracts)
Soy and Heart Disease : Hypercholesterolemic Effects of Soy :
Potential MechanismsAnticholesterolemic Effect of the Undigested Fraction of Soybean Protein
Shigeru Yamamoto, Takashi Yamamoto*, Hei-Mei Chung**, Ming-Fu Wang**, Sumie Shinjo, Tatsushi Komatsu***
Department of Nutrition, Faculty of Medicine, University of the Ryukyus, Okinawa 903-01 Japan
* Fuji Oil Co., Izumisano, Osaka 598 Japan
** Department of Food and Nutrition, Providence University, Taichung, Taiwan,
*** Unit of Nutrition in Hospital, University of Occupational and Environmental Health, Kitakyusyu, 807 Japan.(Purpose) The hypocholesterolemic effect of soybean protein has been confirmed by many researchers in animals and humans. We tried to clarify the mechanisms involved.
(Exp. 1) Sugano and his colleagues have shown that peptide fractions of soybean protein (SP-Peptide) produced in the lumen bind steroids and excrete them into the feces in rats. We tried to confirm it in humans. Young female volunteers with slightly high concentration of serum cholesterol were given diets containing casein or SP-Peptides for about a month. Higher excretion of fecal steroids, higher concentration of HDL-cholesterol and lower concentration of LDL-cholesterol were observed in the SP-Peptide group than in the casein group.
(Exp. 2) Growth, nitrogen balance and other nutritional parameters were compared in rats fed SP or various SP-Peptide fractions. They were similar among all the groups. Thess results together with the results of Exp. 1 indicate that SP-Peptides transport steroids to the lower part of intestine to be excreted and then are themselves absorbed.
(Exp. 3) We fed casein or SP diet to rats for about two months and found not only lower serum cholesterol concentration but also lower abdominal fat in the SP diet group than in the casein group.
(Exp. 4) We tried to confirm the results of Exp. 3 in obese ladies. Subjects were given low energy diets of skimmed milk or SP for 3 weeks. The losses in body weight and fat were greater in the SP group than in the skimmed milk group.
(Exp. 5) The effect of SP on body fat cannot be explained by the increase of steroids in feces, therefore, we hypothesized that very small quantities of SP-Peptides goes into the circulatory system and affect the lipid metabolism. To clarify this we administered saline, SP-Peptides (10mg) or amino acid mixture patterned after SP-Peptides (10mg) to mice through the tail vein daily for 2 weeks. Serum cholesterol concentration was lower in the SP-Peptide group than in the other two groups.
(Conclusion) The results suggest two mechanisms of the anticholesterolemic effect of soybean protein: 1. peptides produced from soybean protein in lumen bind steroids and excrete them into feces but the peptides themselves are absorbed, 2. small quantities of the peptides goes into the circulatory system and affects lipid metabolism.
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