Re: is this true?

yes it does.

you can demonstrate this for yourself with Lugols solution, and olive oil, in which about 50% of the side chains in the oil are oleic, each containing one double bond. add Lugols to olive oil, and shake. the red color disappears as the Iodine is incorporated into the oil. alternatively, the Iodine can be dissolved in carbon tetrachloride to form a purple solution, which when mixed with an olefinic substance will cause disapperance of the purple Iodine color rather rapidly.