View clinical trials related to Vitamin A Deficiency.
Filter by:This is a study to evaluate the effects of vitamin A supplementation program on the vitamin A status of preschool children. All children aged 3-5 years who do not have severe illness and are not planning to move from the study area are eligible. Children whose caregivers agree to sign the consent form will be enrolled in their community and submitted to a longitudinal evaluation of vitamin A status before and after vitamin A supplementation campaign. Vitamin A status will be assessed by measuring serum retinol, retinol binding protein and vitamin A total body pool size using stable isotope dilution methodology.
Minimal human data exist on actual liver vitamin A compared with blood biomarkers. One blood biomarker, the percent of total serum retinol (vitamin A) in the form of retinyl esters, has been suggested to diagnose hypervitaminosis A with cutoffs of 5% and 10%. In this study, investigators aim to compare total liver vitamin A reserves with the percent total serum retinol as retinyl esters to evaluate hypervitaminosis A using autopsy samples from US adults. Investigators also evaluate the sensitivity (the ability of the biomarker to correctly identify those with deficiency) and specificity (the ability of the biomarker to correctly identify those without deficiency) of serum retinol to determine vitamin A deficiency, variation of liver vitamin A concentration among lobes, and liver alpha retinyl ester concentrations, a cleavage product of alpha-carotene, a vitamin A precursor. To conduct the study, matched serum and liver samples were procured from 27 US adult cadavers (from donors age 49-101 years) and their vitamin A biomarkers were analyzed.
An adequate micronutrient status during fetal life and infancy is important for optimal development. Dietary practices during pregnancy, lactation and infancy vary among populations and there is today no clear agreement on what constitutes the best diet, including micronutrient supplementation, during this period. There is consequently no clear agreement on what constitutes an optimal biochemical micronutrient status in mothers and infants. Due to substantial physiological changes in plasma volume, hormones, transport proteins and organ function during these periods, the ordinary reference levels or cut off levels used for biochemical assessment of micronutrient status are unsuited to these groups of patients. The objective of the study is to establish cut off levels for important vitamins and trace elements during pregnancy, lactation and infancy in order to ensure an optimal infant neurodevelopment and to study how micronutrient status influence the immunosystem.
The study involves the participant to receive a 250 mcg Cortrosyn (ACTH) Stimulation Test to test the ability of the body to make Cortisol. If the body is not able to make large amount of Cortisol (Delta Cortisol < 13 mg/dl) from the stimulation test, then the participant will be given additional cortisol like medicine called Solumedrol or matching placebo. If the body is able to make large amounts of Cortisol (> 13 mg/dl), then the participant will receive daily shots of Vitamin A for 7 days or matching placebo. If the participant does not respond to the stimulation test, and meets the criteria for Cortisol deficiency (all 3 cortisol concentrations < 20 mg/dl), then he/she will screen failed for the study and will be offered hydrocortisone as part of routine care by the treating physician.
For assessing body retinol pools in preschool children, it is recommended that a blood sample is taken 14-21 days after isotope dosing. During this period, dietary intake of vitamin A should be controlled. Shortening of this period as has been validated for adults would reduce the burden for the children as well as improve research efficiency. The aim is to validate a 4-day protocol for assessing body retinol pools in preschool children by modelling data derived by retinol isotope dilution (RID) method. Venous blood samples will be collected of 60 children 4 days after dosing of 0.4 mg 13C-labeled retinyl acetate. A second venous blood sample will be collected at 6, 8, 12 hrs; and 1, 2, 4, 7, 11, 16, 22 and 28 days after dosing in subgroups of 6 children, randomly divided over the 10 additional time points. Body retinol pools will be modelled, and the time point at which a parsimonious model applies (presumably at day 4) will be assessed.
Reduced quality of vision and glare in twilight or night are frequently mentioned complaints within the optometric examination. A reason for these problems could be a myopic refractive shift in dark light conditions, commonly known as night myopia or twilight myopia. The aim of this study was to investigate whether quality of vision in twilight or night could be improved by a spectacle correction optimized for mesopic light conditions. Moreover, objective refraction in large pupils measured by aberrometry was compared to subjective mesopic refraction.
This pilot study will evaluate the visual response to infrared (IR) in humans after dark adaptation. The investigators plan to determine which wavelength and intensity the human eye is most sensitive too, using a broad spectrum light source and wavelength-specific bandpass filters. The investigators will then evaluate the electrophysiologic response in healthy humans to IR, followed by studies in those with specific retinal diseases. The long-term goal of this research is to better understand the role that IR plays in visual function, and whether this can be manipulated to allow for vision in certain retinal pathologies that result from loss of photoreceptor cells. The investigators central objective is to test the electrophysiologic response to IR in the dark-adapted retinal and visual pathways. The investigators central hypothesis is that IR evokes a visual response in humans after dark adaptation, and the characteristics of this response suggest transient receptor potential (TRP) channel involvement. The investigators rationale is that a better understanding of how IR impacts vision may allow for an alternative mechanism for vision in a number of diseases that cause blindness from the degradation or loss of function of photoreceptor cells. The investigators will test the investigators hypothesis with the following Aims: Aim 1: To determine the optimal IR wavelength for visual perception in dark-adapted human participants. The investigators hypothesize that the healthy human eye will detect IR irradiation, with a maximum sensitivity at a specific wavelength. Using a broad-spectrum light source with wavelength-specific bandpass filters, the spectral range of visual perception to IR will be evaluated. The same will be done on colorblind participants. Aim 2: To test the electrophysiologic response to IR in healthy humans after dark adaptation. The investigators hypothesize that IR will elicit an amplitude change on electroretinography (ERG) and visual evoked potential (VEP) responses after dark adaptation in healthy human participants. Participants will be tested with both test modalities to evaluate their response to IR. Aim 3: To test the electrophysiologic response to IR after dark adaptation in humans with certain retinal diseases. Participants with retinitis pigmentosa, age related macular degeneration and congenital stationary night blindness, will be tested. Results will be compared to baselines and to those of healthy participants. The investigators hypothesize that there will be a response to IR on ERG and VEP, which will provide clues to the retinal cell layer location of the response to IR and the nature of potential TRP channel involvement.
Corn-soy vitamin and mineral fortified blended foods (FBFs) are primarily used for food aid, although sorghum and cowpea may be suitable alternative FBF commodities. The objective of the Micronutrient Fortified Food Aid Pilot Project (MFFAPP) Tanzania Efficacy Study is to determine whether newly formulated, extruded sorghum- and cowpea-based FBFs have equal, or better, nutritive value and acceptance compared to a traditional corn-soy blend. The effectiveness of each blend will be determined in an efficacy study of Tanzanian children under the age of 5 that are deficient, or at risk for deficiency, in iron and vitamin A.
The purpose of this randomized control trial is to test the impact of provitamin A carotenoid biofortified maize meal consumption on maternal and infant vitamin A status.
The overall objective is to determine the impact of EED on zinc absorption and homeostasis, and its impact on the absorptive capacity of vitamin A absorption of young children (18-24 months of age) in an austere setting with high rates of diarrhea, stunting, and micro-nutrient deficiencies.