Retinyl palmitate (some manufacturers simply call it “Palmitate”) is the main storage form of vitamin A in all fish livers, and is actually a combination of retinol and palmitic acid. Small amounts of “free retinol” may also be present in the liver.
With regards to vitamin A analysis of fish liver oils, there is no need to measure levels of palmitate (the predominant form) and retinol (the minor form) separately. When a fish liver oil sample is sent away for analytical testing to measure the total level of vitamin A, the laboratory will take the sample of liver oil and break all forms of vitamin A present in the liver oil (including the palmitate form) down to the retinol form. The next step is to measure the amount of retinol present and this measurement is therefore a measure of the total vitamin A content for that sample of fish liver oil.
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