Vitamin A (also known as retinol) is a fat-soluble vitamin that plays a crucial role in various physiological functions within the body. It exists in different forms, including retinol (preformed vitamin A found in animal products) and provitamin A carotenoids (found in plant-based foods), which can be converted to active vitamin A in the body.
Key points:
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Functions: It is essential for the formation of visual pigments in the retina, contributing to low-light and color vision. It is also important for the immune system, cell differentiation, gene expression, growth, and development.
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Sources: Animal sources are liver, fish liver oils, egg yolks, and dairy products. Plant sources are colorful fruits and vegetables.
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Deficiency: Can lead to night blindness, dry skin, increased susceptibility to infections, and impaired immune function. In severe cases, it can cause blindness.
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Toxicity: Excessive intake of vitamin A, especially from supplements, can lead to toxicity. Symptoms may include nausea, dizziness, blurred vision, and in severe cases, more serious health issues.
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Recommended Dietary Allowance (RDA): The RDA varies by age, sex, and life stage. It is expressed in both retinol activity equivalents (RAE) and international units (IU).
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Supplementation: For most people, obtaining vitamin A through a balanced diet is sufficient.