Your liquid iodine I am assuming is Lugols Solution. Vit.C, more properly known as ascorbic acid, reacts immediately with elemental iodine in a redox reaction that changes some or all of the elemental iodine into iodide. The issue is not that you lose all benefit by mixing with Vit.C, since the iodide form is used by some tissues, like Thyroid. But you lose some or all of the elemental iodine form when you mix Lugols with Vit.C, and, in turn, you lose some or all of the benefit of the elemental form in that dose that is apparently required or preferred by many tissues, such as breast, ovaries, and prostate. BTW, Kelp acts as a seawater filter and picks up relatively high concentrations of toxins, including arsenic, which is why it really is not a good source of iodine.