Geraldine V. Mitchell

Protein efficiency ratios and net protein ratios of selected protein foods

As a part of a cooperative study initiated to assess bothin vitro andin vivo protein quality methods, the protein efficiency ratio (PER) and net protein ratios (NPR) of 15 different protein sources were determined. Male weanling Sprague-Dawley rats were fed a 10% protein diet. Fourteen-day NPR and relative NPR (RNPR) values and 14- and 28-day PER and relative PER (RPER) values were calculated for each protein source. When protein quality values were expressed relative to ANRC casein, the 14- and 28-day PER data ranked the protein sources essentially in the same order. RPER values of nonfat dried skim milk (unheated) and tuna were more than 100% that of casein; nonfat dried skim milk (heated), chickpeas, and breakfast sausage were between 50 and 70% of that of casein; and pinto beans and rice-wheat gluten cereal did not support substantial growth of the rat. The NPR method did not always rank the protein sources in the same order as the PER method. For the poor quality proteins, RNPR values were much higher than the RPER values; however, the RNPR and RPER values agreed closely for high quality protein sources.

Alterations in β-carotene and vitamin E status in rats fed β-carotene and excess vitamin A.

Abstract The effects of feeding various levels of vitamin A with and without various levels of β-carotene on vitamin E and β-carotene status and hepatic biodegradation capacity were examined. Male weanling Sprague-Dawley rats, 10/group, were fed ad libitum for 8 wk diets containing vitamin A and β-carotene in a 3×3 factorial experimental design. Vitamin A palmitate was given at the National Research Councils recommended requirement level of 4,000 IU/kg of diet (control), 10 times the requirement (vitamin A1) and 100 times the requirement (vitamin A2). Each of these groups was given β-carotene at either 0,48 (BC1) or 480 mg/kg (BC2) of diet. Liver vitamin A levels increased dramatically and were 100-fold higher in vitamin A2 groups than in the control group. Retinyl esters increased in the liver; retinyl stearate increased as a result of β-carotene treatments. Liver β-carotene levels were significantly reduced in vitamin A1-BC2 and vitamin A2-BC2 groups compared to the control-BC2 group. In the vitamin A2-BC2 group, plasma vitamin E was reduced 77% compared to the control group; hepatic microsomal cytochrome P-450 and its isozyme, benzephetamine demethylase, were significantly lower; and the specific activity of glutathione S-transferase was increased. These findings suggest that vitamin E status can be altered by ingesting excessive vitamin A or β-carotene and that vitamin A and β-carotene changed the biodegradation and detoxification capacity of the liver in rats.

Natural tocopherols in a dietary supplement of lutein affect tissue distribution of tocopherols in young rats

The effects of graded levels of Flora GLO (FG), a dietary supplement containing lutein derived from marigold flowers, on tissue concentrations of lutein and α- and γ-tocopherol were determined. Six groups of male weanling Fischer 344 rats (15/group) were fed ad libitum modified AIN-93G diets containing 0%, 0.30%, 0.60%, 1.20%, 2.40%, or 4.80% FG for eight weeks. FG provided 0%, 0.015%, 0.030%, 0.060%, 0.120%, or 0.240% lutein; corresponding levels of tocopherols were ~0%, 0.006%, 0.012%, 0.023%, 0.046%, and 0.092%, respectively. Maximal uptakes of lutein in plasma, spleen, and liver were observed with 4.8% FG. Lutein was not detectable in brain, heart, lung, testes, and kidney. Concentrations of αtocopherol in the plasma (μg/mg triglycerides) were reduced in all rats fed FG (p < 0.05). αTocopherol increased nonlinearly in lung, heart, and spleen with increased FG level. αTocopherol in liver increased with increased dietary FG; αtocopherol in kidney, testes, and brain did not increase. At each dietary level of FG, the spleen had a higher percentage of γtocopherol, and testes and brain had a lower percentage of γtocopherol than all other tissues. For all tissues, the concentrations of αtocopherol were always higher than those of γtocopherol. Tocopherols added to the dietary supplement for functional purposes appeared to have a significant effect on tissue levels of tocopherols. Therefore, changes in α and γtocopherol levels in tissues of rats fed FG cannot be attributed solely to effects of lutein.

Nutritional and pathological changes in male and female rats fed modifications of the AIN-76A diet

Male and female weanling Sprague-Dawley rats were fed either an AIN-76A diet or a modification of the AIN-76A diet containing no added DL-methionine but with higher levels of vitamins, fluoride and magnesium than in the AIN-76A diet. Both diets were fed, to groups of ten rats of each sex, at 18% protein or a reduced protein level of 13% for 12 wk. Within each sex, all diets produced comparable weight gains in rats at the end of 12 wk, except that the reduced-protein modified AIN-76A diet was associated with a reduction in weight gain in male rats. Both diet and protein level had statistically significant effects on the relative weights of some organs, particularly the kidney. The AIN-76A and the reduced-protein AIN-76A diets significantly increased the relative kidney weights (% body weights) of female rats, when compared with the effects of both modified AIN-76A diets (18 and 13% protein). Male rats fed both of the diets containing 18% protein had higher relative kidney weights than did those consuming both 13% protein diets. Females fed the modified diet containing 13% protein had significantly lower liver weights than the other groups. In both sexes, the two diets containing 18% protein caused significantly higher plasma urea nitrogen concentrations than did the lower protein diets. Kidney calcium concentrations varied with the diet, with dietary protein level, and with the sex of the animal. All diets caused small mineral (calcific) concretions of minimal to mild severity in the lumina of scattered renal tubules in the cortex and/or medulla of male rats. All female rats fed the AIN-76A and the reduced-protein AIN-76A diet had large, moderate or severe mineral concretions in the tubules at the corticomedullary junction and this was associated with increased renal calcium levels. The higher concentration of renal calcium at the lower dietary protein level (13%) was associated with severe corticomedullary junction mineralization. The higher protein diets were associated with an increased incidence of hyaline droplets in the cytoplasm of kidney cortical tubules in male rats.

Nutritional assessment of twelve protein foods/ingredients

Abstract The present study was conducted to determine the nutritional value of 12 protein foods/ingredients. Male weanling Sprague-Dawley rats were fed diets containing 10% protein by weight of each of the test samples for 4 weeks. The basal diet contained adequate amounts of all other required nutrients. For foods containing milk protein as the main ingredient, the protein efficiency ratios (PERs) expressed as percentages of ANRC casein ranged from 41 to 129. The PERs of milk-egg blends with different matrices ranged from 89 to 124%. The plant proteins soy protein isolate, defatted peanut protein, and wheat protein isolate had PER values of 72, 56 and 0%, respectively. The single-cell proteins autolyzed yeast and blue-green algae had values of 66 and 78%, respectively. The PER values of nondefatted and defatted liver powder were 33 and 69%, respectively. PER values were positively associated with plasma total protein and albumin levels and negatively associated with blood urea nitrogen levels (P

Supplementation of Rats with a Lutein Mixture Preserved with Vitamin E Reduces Tissue Phylloquinone and Menaquinone-4

The modulation of tissue concentrations of vitamin K by a lutein supplement preserved with natural vitamin E was studied in Fischer 344 rats. Vitamin K is necessary for blood coagulation and may be essential for tissue and bone health. Weanling male rats were fed the AIN-93G diet (control) or modified AIN-93G diets containing 0.3, 0.6, 1.2, 2.4 and 4.8 g supplement/100 g diet for 8 weeks. The supplement contained 5% lutein, 0.22% zeaxanthin and 2.2% natural vitamin E as a preservative. Concentrations of trans-phylloquinone in the plasma (nmol/mmol triglycerides) and heart were significantly reduced (P < or = 0.05) in rats fed the supplement. The reductions in trans-phylloquinone in the heart ranged from approximately 20 to 60% of the control. Concentrations of phylloquinone in the liver were significantly lower in the rats fed the supplement at levels > or = 1.2 g/100 g diet than in the control rats. Ratios of cis/trans phylloquinone in liver and heart increased and concentrations of menaquinone-4 in heart decreased as the dietary level of the lutein supplement increased. The results suggest that the lutein supplement affected the absorption, tissue uptake and/or turnover rate of vitamin K. The presence of other components in the supplement confounded the interpretation of the biological effects of lutein alone on vitamin K metabolism.

Effects of dietary protein on growth and on plasma and liver vitamin A and E levels in young rats

Abstract The effects of dietary protein sources on rat plasma and liver vitamin A and E levels were studied in male weanling rats fed purified 20% protein diets for 28 days. Diets contained adequate amounts of all vitamins and minerals. The food efficiency values expressed as percentages of ANRC casein ranged from 85 to 99 with the exception of liver powder, which was 45. The liver vitamin A levels ranged from 131 to 320 μg/g. The liver vitamin A levels were higher for soy isolate, soy flour, blue-green algae (BGA) and liver powder than for ANRC casein (P

Influence of three dietary sources of choline on liver lipids in rats fed animal or plant protein1

Abstract The interrelationships among choline source (choline chloride, CC, egg lecithin, EL, and soybean lecithin, SL), choline level (0, 0.1 and 0.2% added to the diet) and protein source (lactalbumin, LA, and soy flour, SF) were studied. Male weanling rats were fed purified 10% protein diets adequate in all other vitamins and minerals for 4 weeks. For both protein sources, the addition of each choline source to the diet caused a significant reduction in liver total lipid, triglycerides and cholesterol (P

Dietary vitamin E and β-carotene sources influence vitamin A and E storage in young rats fed marginal and adequate vitamin E

The effects of two vitamin E levels (30 and 75 IU/kg diet) and the interrelation of two vitamin E sources [dl-alpha-tocopheryl acetate (dl-alpha-TA) and d-alpha-tocopheryl acid succinate (d-alpha-TAS)] and three vitamin A sources [retinyl palmitate (RP), all-trans synthetic beta-carotene (SBC), and natural beta-carotene (NBC)] were studied. Dietary vitamin A sources provided 4,000 IU/kg. Twelve groups of Fischer 344 rats (10/group) were fed designated diets for eight weeks. For RP, SBC, and NBC, the increase in each vitamin E source from a marginal to an adequate dietary level caused a significant increase in liver and heart alpha-tocopherol. Among rats fed diets with an adequate level of vitamin E, d-alpha-TAS was not as effective as dl-alpha-TA in increasing liver alpha-tocopherol levels. Plasma retinol was lower in rats fed d-alpha-TAS than in those fed dl-alpha-TA. Among rats fed diets with an adequate level of dl-alpha-TA, those fed SBC had significantly higher liver and heart alpha-tocopherol concentrations than did all other groups (p < 0.05). Liver retinol equivalents for rats fed NBC were approximately 66% lower than those in rats fed SBC or RP (p < 0.05). The roles of the two vitamin E sources in alpha-tocopherol metabolism are not equivalent. These data indicate that vitamin A source influences the magnitude of the tissue vitamin A and E changes in response to the two vitamin E sources.