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Background: Sorghum is the fifth most consumed cereal grain but limiting in the indispensable amino acid lysine. Complementing sorghum with lentils can improve the quality of sorghum-based diets. However, knowledge of lysine bioavailability in sorghum is lacking.Objectives: The study objectives were to determine the bioavailability of lysine in sorghum and to assess the effect of complementation of sorghum and lentils in a mixed-meal format.Methods: We studied 5 healthy young men (≤30 years; BMI <25 kg/m2) in a repeated-measure design using the indicator amino acid oxidation (IAAO) method, with L-[1-13C] phenylalanine as the indicator. Each subject participated in 8 determinations in random order. On the reference diet, subjects received 4 amounts of L-lysine (5, 8, 12, and 15 mg. kg-1 . d-1) from a crystalline amino acid mixture patterned after egg protein. On the test diet, they received 3 levels of lysine (8.2, 12.5, and 15.7 mg. kg-1 . d-1) from sorghum, and on the complementation diet they received 1 level of lysine from a mixed meal of sorghum and lentils. The bioavailability of lysine in sorghum was estimated by comparing the IAAO response to the test diet with the IAAO response to the reference diet using the slope-ratio method. Effectiveness of complementation was assessed by comparing the IAAO response to the mixed meal to the IAAO response to the test protein.Results: The bioavailability of lysine from sorghum was 94%. Upon complementation with lentils, there was a decline in the oxidation of L-[1-13C] phenylalanine by 19% (P < 0.0495), reflecting an improvement in available lysine in the mixed meal due to increased lysine intake.Conclusions: Although the bioavailability of lysine in sorghum is high, its lysine content is limiting. Complementation with lentils in a 1:1 ratio is recommended to achieve the lysine requirement for adult men consuming a sorghum-based diet. This trial was registered at clinicaltrials.gov as NCT03411005. [ABSTRACT FROM AUTHOR]

Background: Descriptive and quantitative information on β-carotene whole-body kinetics in humans is limited.Objectives: Our objective was to advance the development of a physiologically based, working hypothesis compartmental model describing the metabolism of β-carotene and β-carotene-derived retinol.Methods: We used model-based compartmental analysis (Simulation, Analysis and Modeling software) to analyze previously published data on plasma kinetics of [2H8]β-carotene, [2H4]β-carotene-derived retinol, and [2H8]retinyl acetate-derived retinol in healthy, older US adults (3 female, 2 male; 50-68 y); subjects were studied for 56 d after consuming doses of 11 μmol [2H8]β-carotene and, 3 d later, 9 μmol [2H8]retinyl acetate in oil.Results: We developed a complex model for labeled β-carotene and β-carotene-derived retinol, as well as preformed vitamin A, using simulations to augment observed data during model calibration. The model predicts that mean (range) β-carotene absorption (bioavailability) was 9.5% (5.2-14%) and bioefficacy was 7.3% (3.6-14%). Of the absorbed β-carotene, 41% (25-58%) was packaged intact in chylomicrons and the balance was converted to retinol, with 58% (42-75%) transported as retinyl esters in chylomicrons and 0-2% by retinol-binding protein. Most (95%) chylomicron β-carotene was cleared by the liver. Later data revealed differences in the metabolism of retinyl acetate- versus β-carotene-derived retinol; data required that both β-carotene and derived retinol be recycled from extrahepatic tissues (e.g. adipose) in HDL. Of total bioconversion [73% (47-99%)], 82% occurred in the intestine, 17% in the liver, and 0.83% in other tissues.Conclusions: Our model advances knowledge about whole-body β-carotene metabolism in healthy adults, including the kinetics of transport in all lipoprotein species, and suggests hypotheses to be tested in future studies, such as the possibility that retinol derived from hepatic conversion over a long period of time might contribute to plasma retinol homeostasis and total body vitamin A stores. [ABSTRACT FROM AUTHOR]

Background: Pearl millet is the chief source of energy in the diet in some developing regions, but has a limited amount of indispensable amino acid lysine. Complementation with pulses like lentils can improve the protein quality of millet diets, but the knowledge of lysine bioavailability (BA) in millet and lentils is lacking.Objectives: The study objectives were to determine the BA of lysine in millet and lentils separately and to assess the effect of complementation of millet and lentils in a mixed meal format.Methods: We studied 9 healthy young men (≤30 y; BMI <25) in a repeated-measure design using the indicator amino acid oxidation (IAAO) method, with L-[1-13C] phenylalanine as the indicator. Each subject completed 7 or 8 experiments in random order. On the reference diet, subjects received 4 graded levels of L-lysine (5, 8, 12, and 15 mg·kg-1.d-1) from a crystalline amino acid mixture patterned after egg protein; on the test diets, they received 3 levels of lysine (10, 12, and 15 mg·kg-1.d-1) from either steamed millet or stewed lentils; and on the complementation diet, they received 1 level of lysine from a mixed meal of steamed millet and stewed lentils. The BA of lysine and the effect of complementation were assessed by comparing the IAAO responses to the test diets and the complementation diet with the IAAO response to L-lysine intakes in the reference protein, using the slope ratio method.Results: The BA of lysine was 97% from millet and 80% from lentils. Complementation of steamed millet with stewed lentils decreased the oxidation of L-[1-13C] phenylalanine by 27% (P < 0.05), signifying improved quality of the combined millet and lentil protein.Conclusions: Lysine has high BA but is still limiting in steamed pearl millet. Complementation with lentils in a 2:1 ratio is recommended to meet the lysine and protein requirements for adult men consuming a millet-based diet. This trial was registered at clinicaltrials.gov as NCT03674736 and NCT03339167. [ABSTRACT FROM AUTHOR]

Age-related macular degeneration (ARMD) is inversely associated with the accumulation of lutein + zeaxanthin in the macula, but higher lutein intakes are inconsistently related to reduced risk of ARMD in epidemiologic studies. Resolution of efficacy awaits clinical trials designed with knowledge of lutein supplement pharmacokinetics. Lutein bioavailability was determined for lutein diester and unesterified lutein formulations as they might be incorporated into dietary supplements. Healthy subjects (n = 18) consumed a single dose of each formulation (either 0.5 or 0.67 micro mol lutein/kg body, 10 and 8 subjects, respectively) in random order, and the appearance of free lutein + zeaxanthin was measured in serum from 0 to 408 h. Areas under the serum concentration x time curves (AUC), as a measure of bioavailability, were independent of gender, body mass index and lutein dose. The lutein diester formulation was 61.6% more bioavailable than the unesterified lutein formulation with higher mean AUC, maximum serum concentration and ascending slope (P < 0.05). The AUC was greater in 14 of 18 subjects when they consumed the lutein diester formulation. Comparison with data from previous studies suggested that dissolution was a greater limitation to bioavailability than lutein ester hydrolysis because an oil-solubilized unesterified lutein preparation, given at 0.5 micro mol/kg body, resulted in greater mean peak concentrations and AUC compared with either the unesterified or lutein diester formulations used in our study. In conclusion, the lutein diester formulation poses no impediment to lutein bioavailability at the doses tested, but formulation dissolution is an important factor in lutein bioavailability and should be evaluated before a supplement and dose are selected for use in clinical trials. [ABSTRACT FROM AUTHOR]

Soybean isoflavones have been proposed to be anticarcinogenic, but their effective doses have not been established. To study their bioavailability, seven women consumed 3.4, 6.9, or 10.3 mumol isoflavones/kg body wt in soymilk in each of three meals of a liquid diet on one of three feeding days that were separated by 2-wk washout periods. Subjects were randomly assigned to doses in a cross-over design. Plasma, urine and fecal isoflavones were measured by reverse phase HPLC. In two subjects, fecal isoflavone recovery was 10-20 times that in the other five subjects. Average 48-h urinary recoveries of ingested daidzein and genistein were 16 +/- 4 and 10 +/- 4%, respectively, at all three doses among the five subjects excreting only small amounts of isoflavones in feces, whereas urinary recoveries of daidzein and genistein in the two subjects who excreted large amounts of fecal isoflavones were 32 +/- 5 and 37 +/- 6%, respectively. Urinary isoflavone excretion was nearly zero in all subjects at 48 h after dosing. Average plasma concentration of genistein at 24 h after the breakfast isoflavone dose in subjects excreting large amounts of fecal isoflavones was significantly greater by 2.5-fold than in subjects who excreted small amounts of fecal isoflavones (P < 0.05). In vitro anaerobic incubation of isoflavones with human feces showed that intestinal half-life of daidzein and genistein may be as little as 7.5 and 3.3 h, respectively. These data suggest that human isoflavone bioavailability depends upon the relative ability of gut microflora to degrade these compounds. [ABSTRACT FROM AUTHOR]