Vitamin B-6 depletion followed by repletion with animal- or plant-source diets and calcium and magnesium metabolism in young women.

An 84-98-d study was conducted in young women to determine the effect of vitamin B-6-deficient diets on calcium and magnesium metabolism. A vitamin B-6-deficient formula diet fed initially was followed by either animal- or plant-source protein food diets containing four increasing amounts of vitamin B-6. Calcium balance was negative during vitamin B-6 depletion. Serum calcium was higher and calcium balance negative with the plant protein diets. Magnesium balance was negative during vitamin B-6 depletion due to increased urinary magnesium excretion. Urinary calcium decreased during vitamin B-6 depletion and increased as dietary vitamin B-6 increased. Urinary oxalate was significantly higher at the end than at the beginning of vitamin B-6 depletion and was higher with plant than animal protein diets. The results suggest that vitamin B-6 depletion may alter calcium and magnesium metabolism and that dietary components associated with the protein source may influence calcium retention.

Cholesterol-lowering in hamsters fed rice bran at various levels, defatted rice bran and rice bran oil.

This study was conducted to determine the relative cholesterol-lowering effects of several levels of full-fat rice bran in hamsters. In addition, the separate effects of defatted rice bran and/or crude rice bran oil were investigated at levels equivalent to those present in 43.7% full-fat rice bran. Diets containing 10.9, 21.8, 32.8 or 43.7% full-fat rice bran, 35% defatted rice bran and/or 9% rice bran oil were fed to 4-wk-old male hamsters. All diets contained 10% total dietary fiber, 9% fat and 3.2% nitrogen; hypercholesterolemic diets contained 0.3% cholesterol; two diets were cholesterol-free, i.e., 10% cellulose and 43.7% full-fat rice bran. After 21 d, plasma and liver cholesterol, plasma triglycerides and liver weights were significantly greater in hamsters fed the 10% cellulose diet with 0.3% cholesterol compared with those fed the cholesterol-free cellulose diet. In animals fed cholesterol-free diets, plasma cholesterol values were significantly lower in those fed the 43.7% full-fat rice bran diet than in those fed the cellulose diet. In animals fed cholesterol-containing diets, plasma and liver cholesterol were significantly lower in animals fed the 43.7% full-fat rice bran diet than in those fed the cellulose diet. Plasma cholesterol reductions were significantly correlated to the level of rice bran in the diet. In cholesterol-fed hamsters, total liver cholesterol content was significantly lower in those fed the defatted rice bran diet with rice bran oil compared with those fed the cellulose diet. Full-fat rice bran was the only treatment that significantly lowered both plasma and liver cholesterol.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of full-fat or defatted rice bran on serum cholesterol.

Rice bran has been shown to lower serum cholesterol in hamsters. Leghorn cockerel chicks were fed 60% full-fat rice bran (FFRB) and corn/soy (CS) diets with 0.5% added cholesterol. Both diets contained 18% protein. All reported parameters are on blood serum. Significant differences (p less than 0.05) were found in total cholesterol (TC), triglycerides (TG), high-density and low-density lipoprotein cholesterol (HDL and LDL). In a second study, chicks were fed FFRB, defatted rice bran (DFRB), and CS diets balanced for 18% protein, 14.47% total dietary fiber and 10.78% lipid with 0.5% added cholesterol. Both TC and TG were significantly lower (p less than 0.05) in chicks fed FFRB and CS diets. Significant differences were found in HDL values for all diets with FFRB exhibiting the highest mean value (155 mg/dl) and CS exhibiting the lowest mean value (114 mg/dl). All diets were significantly different (p less than 0.05) in LDL, with mean values of 249, 318 and 275 mg/dl for FFRB, DFRB and CS, respectively. FFRB appears to increase HDL and to lower LDL in chicks, but does not always affect TC, whereas DFRB may increase all three serum lipid components.

A stable-isotope study of zinc, copper, and iron absorption and retention by young women fed vitamin B-6-deficient diets.

A 98-d study was conducted in young women to determine the effect of vitamin B-6-deficient diets on zinc, copper, and iron metabolism. Young women were fed vitamin B-6-deficient formula initially, followed by food diets containing four increasing amounts of vitamin B-6. Zinc, copper, and iron absorption, retention, and status were determined at intervals throughout the study. Zinc absorption and retention were greater during vitamin B-6 depletion but serum zinc declined, suggesting that absorbed zinc was not available for utilization. Copper absorption was lower during vitamin B-6 depletion but serum copper was not affected and balance was positive. Iron absorption was not impaired significantly by vitamin B-6-deficient diets but status may have declined. The results suggest that vitamin B-6 depletion of young women may alter zinc metabolism, inhibit copper absorption, and affect iron status. The effects of vitamin B-6 depletion differ markedly among these elements.

Protein utilization by young women consuming animal or plant protein diets at various levels of vitamin B-6 intake.

Eight young women consumed a vitamin B-6 depletion diet (egg albumen formula, less than 0.05 mg vitamin B-6/d) for 11-28 d. Subjects (n = 4) then consumed either animal protein (AP, mainly dairy and poultry products) or plant protein (PP, mainly various types of beans) diets with increasing vitamin B-6 intake (0.5, 1.0, 1.5, and 2.0 mg/d) for periods of 14-21 d. All diets provided 1.55 g protein/kg body wt. Apparent protein digestibility of AP (94.6%) was significantly higher than that of PP (88.4%) diets (p less than 0.001). Protein digestibility was not significantly affected by vitamin B-6 intake. Apparent nitrogen balance of subjects consuming AP diets was slightly, though not significantly, higher than that of subjects fed PP diets. N balance was not influenced by vitamin B-6 intake. Data suggest that short-term low vitamin B-6 intake does not affect protein utilization in humans as determined by digestibility and N balance.

Bioavailability of vitamin B-6 from rat diets containing wheat bran or cellulose.

Bioavailability of vitamin B-6 (B-6) in the total diet was studied in male, weanling Sprague-Dawley rats fed fiber-free (FF) diets with 0.2 or 6.9 mg pyridoxine/kg diet (0-, 2- or 6.9-PYR), 20% wheat bran (WB) diets with 3.9- or 5.5-PYR or 7% cellulose (C) diets with 0- or 2-PYR for 28 d. Body weight gain (mean +/- SEM) with 0-PYR was 70 +/- 9.0 and 81.2 +/- 4.2 g for FF and C, respectively. All other groups gained 170-180 g. Urinary excretion of 4-pyridoxic acid (4-PA), a major B-6 metabolite, for FF groups was 1.31 +/- 0.22, 2.26 +/- 0.28 and 6.39 +/- 1.73 micrograms/24 h, at 0-, 2- and 6.9-PYR, respectively. Rats fed WB diets excreted 4.99 +/- 0.58 and 9.81 +/- 0.76 micrograms/24 h (3.9- and 5.5-PYR, respectively) and those fed C diets excreted 1.46 +/- 0.34 and 2.69 +/- 0.72 micrograms/24 h (0- and 2-PYR). There was increasing turnover and shorter biological half-life of [14C]pyridoxine (1 mu Ci injected on d 1) with increasing dietary B-6. Growth, 4-PA and 14C turnover data indicated that WB contributed to B-6 intake of these rats. Cellulose acted as a simple dietary diluent and had no effect on indices of B-6 status. These data suggest that dietary fiber, as cellulose or the indigestible component of wheat bran, does not adversely affect the bioavailability of vitamin B-6.

Improving protein quality of bread - nutritional benefits and realities.

The bases for improving bread protein quality are critically examined. Protein consumption is shown to be directly related to total calorie intake in many countries, with a correlation coefficient (r) of greater than or equal to 0.90. Concentration of protein in bread, % kilocalories, is similar to that of mixed diets in many parts of the world. Quality of bread protein, when evaluated by male weanling rats, may be improved by supplementation with lysine and threonine, as well as with many protein sources. Human adults, on bread diets, may be maintained in nitrogen equilibrium or slightly positive nitrogen balance. Increases, however, in nitrogen retention have been reported when lysine was added to bread. Laboratory studies with infants and young children, often hospitalized and recovering from severe malnutrition, show that lysine supplementation of wheat flour and gluten diets enhanced nitrogen retention and weight gain. No effect was observed when whole wheat diets were supplemented with lysine. Several field studies with children indicate that the addition of lysine to either supplemental breads provided at school, or to all wheat products consumed, resulted in no observed beneficial effects. Other field studies report an increase in either weight or height with addition of lysine to breads. A laboratory study with human adults suggests that a wheat flour: soy flour mixture has a higher biological value than wheat flour alone. The role, in human nutrition, of breads with improved protein quality remains somewhat obscure.