Jim:
Regarding this statement in a recent article [by M.G.M.] :
“To test your body’s need for iodine, you place a drop on your wrist or foot, if it absorbs within four hours, your body is in need of iodine. (You will want to slowly build up [with an incrementally larger area of skin covered], over months so as not to disrupt your thyroid), if the mark stays close to eight hours, then you are sufficient in iodine. Your body will soak it up if you need it.”
This is an old wives’ tale. The visibility of iodine on the skin is influenced by a great many things, but least of all by the amount of iodine already in the body.
This paper contains the following text:
“From the published data, the skin iodine patch test is not a reliable method to assess whole body sufficiency for iodine. Many factors play a role in the disappearance of the yellow color of iodine from the surface of the skin. For example, if iodine is reduced to iodide by the skin, the yellow color of iodine will disappear because iodide is white. In order to regenerate iodine on the skin, one needs to apply an oxidant such as hydrogen peroxide, complicating the test further. The evaporation of iodine from the skin increases with increased ambient temperatures and decreased atmospheric pressure due to weather conditions and altitude. For example, the yellow color of iodine will disappear much faster in Denver, Colorado at 5,000 feet above sea level then Los Angeles, California at sea level, irrespective of the amount of bioavailable iodine.”
The data in the paper also suggests that this test can’t work as described, because the body will absorb far more iodine than it needs.
That paper references this paper which states:
“The percentage of iodine penetration through the skin is the same, irrespective of whether the cells have a high or low vitality, or are dead, and irrespective of the direction of penetration. Activity of the cells, therefore, does not seem to be indispensable for the penetration of iodine.”
That seems pretty conclusive. – P.N.G.