Different supplement levels of nicotinic acid (NiA) (0mg for 3 days, 25mg/day for 3 days, 0mg for 1 day and 50mg/day for 3 days) were administered to five healthy men aged 19-20 years fed a niacin-controlled diet, then the blood concentration and urinary excretion of niacin derivatives were measured. Blood NAD was maintained at an almost constant level (26.2nmol/ml), independent of the dosage of NiA. The increase in the blood niacin level during the 50mg NiA administration period suggested that the maximum rate of metabolism of NiA to NAD was 40-55mg/24h. Urinary excretion of N¹-methylnicotinamide (MNA), on the third day in each period was increased in proportion to the dosage level, whereas urinary niacin excretion remained unchanged relative to the observed blood niacin level. From these results, it is concluded that the rate of urinary MNA excretion could be useful as a quantitative index of niacin intake in humans, at least under the controlled experimental conditions employed here.

View full abstract

Hypercholesterolemic diets containing 15% fat at five different n-3/n-6 ratios (0.03, 0.14, 0.29, 0.60 and 1.26) were given to male Sprague-Dawley rats for two weeks, and then the lipid concentrations and fatty acid compositions of lipid fractions in serum and liver were determined. The dietary n-3/n-6 ratio sufficiently effective for reducing the serum total cholesterol (TC) and phospholipid (PL) concentrations in dietary hypercholesterolemic rats was found to be between 0.14 and 0.29. The serum triglyceride concentration did not necessarily respond to changes in the n-3/n-6 ratio. Liver lipids were slightly affected by variation of the dietary n-3/n-6 ratio. The fatty acid compositions of serum and liver lipid fractions were affected by changes in the dietary n-3/n-6 ratio. In the PL fraction of serum and liver, the proportions of C18: 2 n-6 and C20: 4 n-6 and the ratio of C22: 6/C20: 5 were decreased, whereas the proportions of C20: 5 n-3 and C22: 6 n-3 and the ratios of n-3/n-6 and C20: 5/ C20: 4 were increased with elevation of the dietary n-3/n-6 ratio. The P/S ratio in serum PL decreased, but that in liver PL did not change. Significant reductions of the C20: 4/C18: 2 ratio in each of the lipid fractions of serum and liver were observed in the groups containing a dietary n-3/n-6 ratio of more than 0.14, suggesting that conversion of C18: 2 to C20: 4 is effectively inhibited by a comparatively small amount of n-3 PUFA (approximately one seventh of n-6 PUFA).

View full abstract

The effects of dietary fiber on plasma cholesterol, the level of steroid in intestinal contents and feces, and short-chain fatty acid (SCFA) in cecum and feces were studied in 8-week-old male Wistar rats. The rats were fed a cholesterol-free diet containing 5% dietary fiber (cellulose, bacterial cellulose, apple pulp, gum arabic, guar gum, guar gum hydrolysate) with meals provided twice daily for 2 weeks. At 3.5h after the last meal, the animals were sacrificed. Only guar gum significantly decreased the level of plasma cholesterol and increased fecal bile acid and total steroid excretion. However, there was no relationship between the plasma cholesterol concentration and fecal total steroid or bile acid excretion, when data obtained from all rats were combined. Plasma cholesterol concentration was negatively correlated with bile acid content in the upper small intestine. In rats except those in the guar gum hydrolysate group, there was a negative relationship between plasma cholesterol concentration and SCFA content, especially propionate, in the cecum. These results demonstrate that fecal steroid excretion, bile acid secretion and propionate production in the cecum may be involved in the mechanism responsible for the plasma cholesterol-lowering effects of dietary fiber.

View full abstract

Effects of dietary casein phosphopeptide (CPP) on the calcium (Ca) balance, breaking force of the femur and soluble Ca contents of the small intestine of young growing rats were studied. In experiment 1, male Sprague Dawley rats, divided on weaning into four groups, were fed a control diet (isolated soy protein, ISP; 20%) or a CPP diet (ISP; 17.1%, CPP; 3.5%, CPP/Ca (w/w); 10) for 4 or 8 weeks, respectively. In experiment 2, rats were fed a control or a CPP diet (CPP/Ca; 0.35, 2.5, 5.0, 7.5 and 10.0) for 4 weeks. All diets contained the same amounts of Ca (0.35%) and phosphorus (0.70%). A Ca balance study was performed at the 4th or 8th week. Body weight gains were not significantly different among the groups. The Ca balance was increased to a greater extent in the CPP diet groups than in the control diet groups at both the 4th and 8th weeks, with decreased excretion of fecal Ca. An increase in the Ca balance as well as the plasma Ca concentration within the physiologically normal range was observed in the r ts fed CPP with a weight ratio of CPP/Ca of more than 0.35. However, the dose-dependent increase in these values was not significant. The wet weight and Ca contents of the femur increased in the CPP diet groups, with no changes in the breaking force. The amount of Ca in the luminal contents of the small intestine 2h after CPP feeding was higher than those in the control rats. These results suggest that CPP supplementation may have a significant effect on Ca availability, at least under conditions of lower dietary Ca.

View full abstract

The intestinal absorption of calcium-casein peptide (CaCP) was investigated in rats under unanesthetized and unrestrained conditions using a new modified portal cannulation method. CaCP is a hydrolysate of calcium caseinate with an average peptide chain length of 4.7 and containing 7.3% free amino acids. We compared the intestinal absorption of CaCP with that of an amino acid mixture (AAM) corresponding to CaCP by determining total amino acids, total essential amino acids and individual amino acids in portal blood after a single dose delivered into the duodenum. It was found that CaCP was absorbed more rapidly than AAM, and that the amount of amino acids absorbed was also increased significantly. In particular, the rate of absorption of essential amino acids of CaCP was markedly higher than that of AAM. However, the proportion of each amino acid absorbed in the portal blood from CaCP was not necessarily similar to the amino acid composition administered. These results suggest that the intestinal absorption of CaCP is considerally superior to that of AAM, and that CaCP could thus have improved nutritional effects.

View full abstract

Effects of added foodstuffs and chemicals on the evolution of offensive odor during storage of porcine small intestine at 20°C were studied. The effects were evaluated in terms of sensory scores, total bacterial counts, and amounts of evolved volatiles. Among the additives found most effective in terms of sensory score in suppressing offensive odor development were onion, perilla, miso, a blend of ginger and soy sauce, green tea, sage, thyme, clove, allspice, chervil and lemonbalm. A blend of ginger and soy sauce, green tea and clove inhibited microbial growth during storage. However, no consistent relationship was detected among sensory scores, total bacterial counts and amounts of evolved volatiles. This inconsistency may be due to the fact that the action of the tested additives may not be restricted to a single one, but to diverse combinations including preservative, antioxidant, odor-masking or adsorption or incentive effects. Chemicals known to be antioxidants, chelators and sterilizers, such as BHA, EDTA, mercuric chloride and phenol, retarded the evolution of offensive odor and bacterial growth. The amounts of volatiles evolved, especially those of sulfur compounds and alcohols, paralleled the total counts of bacteria and also the sensory scores. Thus it appears that the evolution of the offensive odor during storage of porcine small intestine is largely attributable to microbial growth and the concomitant production of odor volatiles, especially sulfur compounds and alcohols.

View full abstract

Streptococcus faecalis R. ATCC 8043, a lactic acid bacterial strain used for the microbial assay of vitamin B₆, is known to grow on alanine without addition of vitamin B₆. It is evident that the strain requires vitamin B₆ or one of the stereoisomers of alanine as an essential factor for growth. Cells grown on one alanine isomer in a medium deficient in vitamin B₆ contain another type of stereoisomer of alanine as a constitutive element. The relative molecular ratio of the L-form of cellular alanine ranges from about 70% to 85%, even in cells grown on D-alanine as a growth factor. Cells grown on alanine produce vitamin B₆-independent alanine racemase, indicating that the cells can racemize the stereoisomers in the absence of vitamin B₆. Although alanine and vitamin B₆ apparently stimulate the growth of Streptococcus faecalis R. ATCC 8043 in a similar manner, the mechanisms responsible for the growth stimulation by alanine and vitamin B₆ are essentially different; vitamin B₆ is used for the formation of the holo-enzyme of alanine transaminase, which is involved in the biosynthesis of alanine, whereas alanine acts as an essential growth factor.

View full abstract

Glutathione in various foods was determined by HPLC separation, after extraction with 1% perchloric acid, which was effective for removal of protein and stabilization of glutathione in the reduced form (GSH). For determination of GSH and glutathione in the oxidized form (GSSG), the HPLC effluent was monitored by UV absorbance. For selective determination of GSH, it was converted to the N- (acridinyl) maleimide (NAM) derivative before HPLC separation, and monitored by fluorescence. Bound glutathione (B-GSH) was thoroughly reduced electrolytically with a 2-mA electrical current for 10min, enabling total glutathione (T-GSH) to be readily determined. Milk cocoa powder and canned drinks, i. e. orange drink, honey lemon soda, cocoa drink and oolong tea, were supplemented with yeast extract. They were then stored within a temperature range of 3 to 37°C for 3 months. At 3°C, the GSH content was maintained in all of the samples. At 37°C, 81% of the GSH content remained in milk cocoa powder, but only 10% remained in canned acidic drinks, i. e. orange drink and honey lemon soda. On the other hand, the content of B-GSH did not change over the tested temperature range in any of the foods. Thus it is suggested that the contents of GSH and T-GSH in food can be determined by a combination of the NAM method and the electrical reduction method.

View full abstract