The primary form of vitamin A stored in the liver is retinyl esters.
The liver plays a crucial role in vitamin A metabolism. While the liver doesn't produce vitamin A from scratch, it is the main storage site for it. Retinol (another form of vitamin A) and carotenoids (precursors to vitamin A) circulate in the blood, but the liver converts retinol into retinyl esters for efficient storage.
Here's a breakdown:
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Vitamin A Sources: Vitamin A comes from two primary sources:
- Preformed vitamin A (retinol): Found in animal products like liver, dairy, and fish.
- Provitamin A carotenoids (beta-carotene): Found in plant-based foods like carrots, sweet potatoes, and leafy greens.
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Liver's Role:
- The liver takes up retinol from the bloodstream.
- It converts retinol into retinyl esters, which are a more stable storage form.
- When the body needs vitamin A, the liver hydrolyzes retinyl esters back into retinol and releases it into the bloodstream.
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Measurement: Retinol and carotenoid levels are measured in the blood (plasma or serum) for assessment, while the majority of vitamin A is stored in the liver as retinyl esters.
Therefore, while the liver doesn't synthesize vitamin A de novo, it's responsible for converting and storing it as retinyl esters for later use by the body.
