|MadSci Network: General Biology|
Vitamin D is manufactured by animals, with the largest amounts being found in fatty fish and fish oils. Small amounts of Vitamin D are found in milk and most milk is fortified with added Vitamin D as are many bread and cereal products. Vitamin D helps in the absorption of calcium, also found in sardines. Thus for sardines it is a win-win; calcium and Vitamin D. Vitamin D occurs at high levels naturally in sardines. Compared to vitamin fortified whole milk, sardines contain about 6X as much Vitamin D. The best naturally occurring source of Vitamin D is fatty fish and fish oils, including sardines, salmon, mackerel and cod liver oil. The most interesting thing is that herring, which is what is used in the United States for sardines, is not so much of a superior producer of Vitamin D but rather an accumulator of Vitamin D. There are chemistry issues as to why herring have Vitamin D, but as to why herring are higher in Vitamin D: Fish synthesize Vitamin D, a steroid. This compound is fat- soluble and is not passed as a waste metabolite like some other vitamins. So in fatty fish such as herring, salmon, mackerel the compound accumulates in fatty tissues. With thanks for much of the above text to Bruce Love of the Stinson Canning Company in Maine.
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