What Is Vitamin A? Other Names: 3-Dehydroretinol, Antixerophthalmic Vitamin, Axerophtholum

What is Vitamin A?

This post was written with Consensus AI Academic Search Engine – please read our Disclaimer at the end of this article. Vitamin A is a fat-soluble vitamin essential for various bodily functions, including vision, immune system performance, and cellular communication. It exists in two primary forms: preformed vitamin A (retinol and its esterified form, retinyl ester) and provitamin A carotenoids (such as beta-carotene), which are converted into retinol in the body. Other names include: 3-Dehydroretinol, 3-Déhydrorétinol, Acétate de Rétinol, Antixerophthalmic Vitamin, Axerophtholum, Dehydroretinol, Déhydrorétinol, Fat-Soluble Vitamin, Oleovitamin A, Palmitate de Rétinol, Retinoid, Retinoids, Rétinoïdes, Retinol, Rétinol, Retinol Acetate, Retinol Palmitate, Retinyl Acetate, Rétinyl Acétate, Retinyl Palmitate, Rétinyl Palmitate, Vitamin A Acetate, Vitamin A Palmitate, Vitamin A1, Vitamin A2, Vitamina A, Vitamine A, Vitamine A1, Vitamine A2, Vitamine Liposoluble, Vitaminum A.

Biological Functions

Vitamin A plays a crucial role in maintaining healthy vision, particularly in low-light conditions. It is a component of rhodopsin, a protein in the eyes that absorbs light in the retinal receptors. Additionally, vitamin A supports the immune system by maintaining the integrity and function of skin and mucosal cells, which act as barriers to infections1 2.

Health Benefits of Vitamin A

Vision and Eye Health

Vitamin A is vital for preventing night blindness and may reduce the risk of age-related macular degeneration. It is also essential for the maintenance of corneal health and overall eye function1.

Immune System Support

Vitamin A enhances the immune response by promoting the production and function of white blood cells, which help capture and clear pathogens from the bloodstream. This vitamin is particularly beneficial in reducing the severity and duration of infections1 2.

Growth and Development

Vitamin A is essential for cellular growth and differentiation, making it crucial for fetal development and the growth of children. It has been shown to improve linear growth in children with vitamin A deficiency3.

Clinical Applications of Vitamin A

Urinary Tract Infections

Vitamin A supplementation has been found effective in improving clinical symptoms of urinary tract infections (UTIs) and reducing renal scarring in girls with acute pyelonephritis. This is attributed to its anti-inflammatory properties and role in the re-epithelialization of damaged mucosal surfaces1.

Chronic Lung Disease in Infants

In extremely-low-birth-weight infants, vitamin A supplementation has been shown to reduce the risk of chronic lung disease and sepsis, highlighting its importance in neonatal care2.

Ulcerative Colitis

Vitamin A supplementation has demonstrated positive effects in reducing disease activity in patients with ulcerative colitis, suggesting its potential role in managing inflammatory bowel diseases4.

Public Health Implications

Maternal and Child Health

Vitamin A supplementation in women of reproductive age has been studied for its potential to reduce pregnancy-related mortality, although results have been mixed. In some regions, such as Ghana, supplementation did not significantly impact maternal survival rates5. However, in children, vitamin A supplementation has been associated with reduced morbidity from diseases like measles and improved growth outcomes in the presence of infections such as HIV and malaria7 10.

Nutritional Programs

High-dose vitamin A supplementation is often included in public health programs to combat vitamin A deficiency, particularly in developing countries. These programs aim to reduce childhood mortality and improve overall health outcomes6 8.

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Adverse Effects of Vitamin A

Respiratory and Infectious Illnesses

Increased Respiratory Illnesses: High-dose vitamin A supplements have been associated with an increased incidence of acute respiratory illnesses (ARI) and acute lower respiratory illnesses (ALRI) in children with adequate nutritional status2 4.

Higher Risk of Respiratory Symptoms: Children receiving high-dose vitamin A supplements showed higher prevalence rates of respiratory symptoms such as cough and rapid respiratory rate1 4.

Gastrointestinal Issues

Diarrhea: Vitamin A supplementation has been linked to an increased incidence of diarrhea in children under 30 months of age, although it may reduce diarrhea in older children2 4.

Neurological Effects

Bulging Fontanelle: Infants receiving high doses of vitamin A showed a higher incidence of bulging fontanelle, indicating increased intracranial pressure3 5 8 10.

Biochemical Changes

Increased C-Reactive Protein (CRP): Long-term high-dose vitamin A supplementation in multiple sclerosis patients led to an increase in CRP levels, indicating inflammation6.

Vaccine Interactions

Adverse Reactions with Vaccines: Vitamin A supplementation can cause sex-differential adverse reactions when administered with vaccines, including increased local reactions to the measles vaccine8.

Mortality and Severe Outcomes

No Significant Impact on Mortality: Some studies found no significant difference in mortality rates between vitamin A and placebo groups, but noted potential non-lethal adverse outcomes10.

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How has Vitamin A Improved Patient Outcomes?

Urinary Tract Infections (UTIs) and Acute Pyelonephritis (APN)

Improvement in Symptoms and Reduction in Renal Scarring: Vitamin A supplementation significantly reduced the duration of fever, urinary frequency, and poor feeding in girls with APN. It also decreased the incidence of renal scarring compared to the placebo group1.

Ulcerative Colitis (UC)

Reduction in Disease Activity: Patients with UC who received vitamin A supplementation showed significant decreases in disease activity scores and improved clinical response and mucosal healing compared to the placebo group2.

Ischemic Stroke

Improvement in Clinical Outcomes: A combination of vitamin A and D supplementation in ischemic stroke patients led to significant improvements in clinical outcomes, including reduced levels of the inflammatory marker IL-1β and better scores on the National Institute of Health Stroke Scale (NIHSS)3.

Chronic Myelogenous Leukemia (CML)

Potential for Enhanced Survival: Although not statistically significant, patients with CML receiving vitamin A alongside busulfan showed longer durations of clinical progression-free survival and overall survival compared to those receiving busulfan alone4.

Very Low Birth Weight (VLBW) Neonates

Reduction in Mortality and Oxygen Requirement: Early postnatal oral vitamin A supplementation in VLBW infants significantly reduced the composite incidence of all-cause mortality and oxygen requirement, along with other complications such as late-onset sepsis and patent ductus arteriosus5.

Sepsis

No Significant Benefit: High-dose vitamin A supplementation in sepsis patients did not significantly reduce ICU stay, days on ventilator, or 28-day mortality rates compared to the placebo group6.

COVID-19

Ongoing Research: A study protocol suggests that vitamin A, along with other vitamins, may improve severity and mortality rates in ICU patients with COVID-19, but results are pending7.

Multiple Sclerosis (MS)

Improvement in Functional Composite Scores: Vitamin A supplementation improved the Multiple Sclerosis Functional Composite (MSFC) score in patients with relapsing-remitting MS, although it did not significantly affect the Expanded Disability Status Scale (EDSS), relapse rate, or brain lesions9.

Reduction in Fatigue and Depression: MS patients receiving vitamin A showed significant improvements in fatigue and depression scores10.

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Vitamin A Mechanisms of Action

Gene Expression Regulation

Vitamin A and its derivatives, such as retinoic acid, modulate gene expression by binding to nuclear receptors. These receptors include retinoic acid receptors (RARs) and retinoid X receptors (RXRs), which form heterodimers and regulate the transcription of target genes involved in cell differentiation, proliferation, and immune responses1 5 7.

Lipid Metabolism

Vitamin A influences lipid metabolism by regulating the expression of genes involved in cholesterol efflux and tissue lipid homeostasis. In vitamin A deficiency (VAD), there is a decrease in the expression of liver X receptor α (LXRα) and RXRα/β, leading to altered lipid metabolism and immune environment in the kidneys1.

Erythropoiesis

Vitamin A supplementation can enhance erythropoiesis by increasing the production of erythropoietin (EPO), which stimulates red blood cell production. This effect is particularly noted in populations with poor vitamin A and iron status, where vitamin A helps mobilize iron from hepatic stores to support increased erythropoiesis2.

Cognitive Function and Gut-Brain Axis

Vitamin A deficiency exacerbates cognitive deficits and alters gut microbiota composition, which in turn affects neurological functions. VAD leads to decreased expression of vitamin A-related receptors and enzymes in the brain, increased amyloid-β peptides, and altered gut microbiota, contributing to cognitive impairments3.

Glucocorticoid Metabolism

Vitamin A decreases the activity of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), an enzyme that converts inactive glucocorticoids to active forms. This reduction in 11β-HSD1 activity can help ameliorate obesity and metabolic syndrome by decreasing active glucocorticoid levels in adipose tissue4.

Immune Modulation

Vitamin A modulates immune responses by influencing the expression of cytokines and immune-related genes. It affects the expression of RARs in immune cells, which can downregulate inflammatory responses and support immune regulation5 7.

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Common Complaints Associated with Vitamin A Use

Gastrointestinal Symptoms

Gastrointestinal Discomfort: Vitamin A supplementation has been linked to gastrointestinal symptoms, particularly in patients with pre-existing conditions like ulcerative colitis. These symptoms can include nausea, vomiting, and abdominal pain1.

Overdose and Toxicity

Hypervitaminosis A: Excessive intake of Vitamin A can lead to toxicity, known as hypervitaminosis A. Symptoms of this condition include headache, dizziness, nausea, and even more severe effects like liver damage and increased intracranial pressure1.

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Disclaimer

The content presented in this blog is generated by Consensus, an AI-powered academic search engine, and is based on publicly available scientific literature. While every effort is made to provide accurate, up-to-date, and well-researched information, the content is intended for informational and educational purposes only. It does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional before making any decisions regarding medical conditions, treatments, or medications. The AI system’s analysis may not cover all perspectives, emerging research, or individual cases, and it is not a substitute for professional expertise. Neither the blog publisher nor the developers of the AI-powered search engine are responsible for any actions taken based on the information provided in this content. Use of this information is at your own risk. Citations to the original scientific studies are included for reference, but these studies should be reviewed in full and interpreted with the guidance of a healthcare or research professional.

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